This is groff.info, produced by makeinfo version 7.0.3 from groff.texi. This manual documents GNU 'troff' version 1.23.0. Copyright © 1994-2023 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License". INFO-DIR-SECTION Typesetting START-INFO-DIR-ENTRY * Groff: (groff). The GNU roff document formatting system. END-INFO-DIR-ENTRY  File: groff.info, Node: Top, Next: Introduction, Prev: (dir), Up: (dir) GNU 'troff' *********** * Menu: * Introduction:: * Invoking groff:: * Tutorial for Macro Users:: * Major Macro Packages:: * GNU troff Reference:: * File Formats:: * Copying This Manual:: * Request Index:: * Escape Sequence Index:: * Operator Index:: * Register Index:: * Macro Index:: * String Index:: * File Keyword Index:: * Program and File Index:: * Concept Index:: This manual documents GNU 'troff' version 1.23.0. Copyright © 1994-2023 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".  File: groff.info, Node: Introduction, Next: Invoking groff, Prev: Top, Up: Top 1 Introduction ************** GNU 'roff' (or 'groff') is a programming system for typesetting documents. It is highly flexible and has been used extensively for over thirty years. * Menu: * Background:: * What Is groff?:: * groff Capabilities:: * Macro Package Intro:: * Preprocessor Intro:: * Output Device Intro:: * Conventions Used in This Manual:: * Installation:: * Credits::  File: groff.info, Node: Background, Next: What Is groff?, Prev: Introduction, Up: Introduction 1.1 Background ============== M. Douglas McIlroy, formerly of AT&T Bell Laboratories and present at the creation of the Unix operating system, offers an authoritative historical summary. The prime reason for Unix was the desire of Ken [Thompson], Dennis [Ritchie], and Joe Ossanna to have a pleasant environment for software development. The fig leaf that got the nod from ... management was that an early use would be to develop a "stand-alone" word-processing system for use in typing pools and secretarial offices. Perhaps they had in mind "dedicated", as distinct from "stand-alone"; that's what eventuated in various cases, most notably in the legal/patent department and in the AT&T CEO's office. Both those systems were targets of opportunity, not foreseen from the start. When Unix was up and running on the PDP-11, Joe got wind of the legal department having installed a commercial word processor. He went to pitch Unix as an alternative and clinched a trial by promising to make 'roff' able to number lines by tomorrow in order to fulfill a patent-office requirement that the commercial system did not support. Modems were installed so legal-department secretaries could try the Research machine. They liked it and Joe's superb customer service. Soon the legal department got a system of their own. Joe went on to create 'nroff' and 'troff'. Document preparation became a widespread use of Unix, but no stand-alone word-processing system was ever undertaken. A history relating 'groff' to its predecessors 'roff', 'nroff', and 'troff' is available in the 'roff(7)' man page.  File: groff.info, Node: What Is groff?, Next: groff Capabilities, Prev: Introduction, Up: Introduction 1.2 What Is 'groff'? ==================== 'groff' (GNU 'roff') is a typesetting system that reads plain text input files that include formatting commands to produce output in PostScript, PDF, HTML, DVI, or other formats, or for display to a terminal. Formatting commands can be low-level typesetting primitives, macros from a supplied package, or user-defined macros. All three approaches can be combined. A reimplementation and extension of the typesetter from AT&T Unix, 'groff' is present on most POSIX systems owing to its long association with Unix manuals (including man pages). It and its predecessor are notable for their production of several best-selling software engineering texts. 'groff' is capable of producing typographically sophisticated documents while consuming minimal system resources.  File: groff.info, Node: groff Capabilities, Next: Macro Package Intro, Prev: What Is groff?, Up: Introduction 1.3 'groff' Capabilities ======================== GNU 'troff' is a typesetting document formatter; it provides a wide range of low-level text and page operations within the framework of a programming language. These operations compose to generate footnotes, tables of contents, mathematical equations, diagrams, multi-column text, and other elements of typeset works. Here is a survey of formatter features; all are under precise user control. * text filling, breaking, alignment to the left or right margin; centering * adjustment of inter-word space size to justify text, and of inter-sentence space size to suit local style conventions * automatic and manual determination of hyphenation break points * pagination * selection of any font available to the output device * adjustment of type size and vertical spacing (or "leading") * configuration of line length and indentation amounts; columnation * drawing of geometric primitives (lines, arcs, polygons, circles, ...) * setup of stroke and fill colors (where supported by the output device) * embedding of hyperlinks, images, document metadata, and other inclusions (where supported by the output device)  File: groff.info, Node: Macro Package Intro, Next: Preprocessor Intro, Prev: groff Capabilities, Up: Introduction 1.4 Macro Packages ================== Elemental typesetting functions can be be challenging to use directly with complex documents. A "macro" facility specifies how certain routine operations, such as starting paragraphs, or printing headers and footers, should be performed in terms of those low-level instructions. Macros can be specific to one document or collected together into a "macro package" for use by many. Several macro packages available; the most widely used are provided with 'groff'. They are 'man', 'mdoc', 'me', 'mm', 'mom', and 'ms'.  File: groff.info, Node: Preprocessor Intro, Next: Output Device Intro, Prev: Macro Package Intro, Up: Introduction 1.5 Preprocessors ================= An alternative approach to complexity management, particularly when constructing tables, setting mathematics, or drawing diagrams, lies in preprocessing. A "preprocessor" employs a domian-specific language to ease the generation of tables, equations, and so forth in terms that are convenient for human entry. Each preprocessor reads a document and translates the parts of it that apply to it into GNU 'troff' input. Command-line options to 'groff' tell it which preprocessors to use. 'groff' provides preprocessors for laying out tables ('gtbl'), typesetting equations ('geqn'), drawing diagrams ('gpic' and 'ggrn'), inserting bibliographic references ('grefer'), and drawing chemical structures ('gchem'). An associated program that is useful when dealing with preprocessors is 'gsoelim'.(1) (*note Preprocessor Intro-Footnote-1::) 'groff' also supports 'grap', a preprocessor for drawing graphs. A free implementation of it can be obtained separately. Unique to 'groff' is the 'preconv' preprocessor that enables 'groff' to handle documents in a variety of input encodings. Other preprocessors exist, but no free implementations are known. An example is 'ideal', which draws diagrams using a mathematical constraint language.  File: groff.info, Node: Preprocessor Intro-Footnotes, Up: Preprocessor Intro (1) The 'g' prefix is not used on all systems; see *note Invoking groff::.  File: groff.info, Node: Output Device Intro, Next: Installation, Prev: Preprocessor Intro, Up: Introduction 1.6 Output Devices ================== GNU 'troff''s output is in a device-independent page description language, which is then read by an "output driver" that translates this language into a file format or byte stream that a piece of (possibly emulated) hardware understands. 'groff' features output drivers for PostScript devices, terminal emulators (and other simple typewriter-like machines), X11 (for previewing), TeX DVI, HP LaserJet 4/PCL5 and Canon LBP printers (which use CaPSL), HTML, XHTML, and PDF.  File: groff.info, Node: Installation, Next: Conventions Used in This Manual, Prev: Output Device Intro, Up: Introduction 1.7 Installation ================ Locate installation instructions in the files 'INSTALL', 'INSTALL.extra', and 'INSTALL.REPO' in the 'groff' source distribution. Being a GNU project, 'groff' supports the familiar './configure && make' command sequence.  File: groff.info, Node: Conventions Used in This Manual, Next: Credits, Prev: Installation, Up: Introduction 1.8 Conventions Used in This Manual =================================== We apply the term "groff" to the language documented here, the GNU implementation of the overall system, the project that develops that system, and the command of that name. In the first sense, 'groff' is an extended dialect of the 'roff' language, for which many similar implementations exist. The 'roff' language features several major categories for which many items are predefined. Presentations of these items feature the form in which the item is most commonly used on the left, and, aligned to the right margin, the name of the category in brackets. -- Register: \n[example] The register 'example' is one that that 'groff' _doesn't_ predefine. You can create it yourself, though; see *note Setting Registers::. To make this document useful as a reference and not merely amiable bedtime reading, we tend to present these syntax items in exhaustive detail when they arise. References to topics discussed later in the text are frequent; skip material you don't understand yet. We use Texinfo's "result" (=>) and error-> notations to present output written to the standard output and standard error streams, respectively. Diagnostic messages from the GNU 'troff' formatter and other programs are examples of the latter, but the formatter can also be directed to write user-specified messages to the standard error stream. The notation then serves to identify the output stream and does not necessarily mean that an error has occurred.(1) (*note Conventions Used in This Manual-Footnote-1::) $ echo "Twelve o'clock and" | groff -Tascii | sed '/^$/d' => Twelve o'clock and $ echo '.tm all is well.' | groff > /dev/null error-> all is well. Sometimes we use => somewhat abstractly to represent formatted text that you will need to use a PostScript or PDF viewer program (or a printer) to observe. While arguably an abuse of notation, we think this preferable to requiring the reader to understand the syntax of these page description languages. We also present diagnostic messages in an abbreviated form, often omitting the name of the program issuing them, the input file name, and line number or other positional information when such data do not serve to illuminate the topic under discussion. Most examples are of 'roff' language input that would be placed in a text file. Occasionally, we start an example with a '$' character to indicate a shell prompt, as seen above. You are encouraged to try the examples yourself, and to alter them to better learn 'groff''s behavior. Our examples frequently need to direct the formatter to set a line length (with '.ll') that will fit within the page margins of this manual. We mention this so that you know why it is there before we discuss the 'll' request formally.(2) (*note Conventions Used in This Manual-Footnote-2::)  File: groff.info, Node: Conventions Used in This Manual-Footnotes, Up: Conventions Used in This Manual (1) Unix and related operating systems distinguish standard output and standard error streams _because_ of 'troff': . (2) *Note Line Layout::.  File: groff.info, Node: Credits, Prev: Conventions Used in This Manual, Up: Introduction 1.9 Credits =========== We adapted portions of this manual from existing documents. James Clark's man pages were an essential resource; we have updated them in parallel with the development of this manual. We based the tutorial for macro users on Eric Allman's introduction to his 'me' macro package (which we also provide, little altered from 4.4BSD). Larry Kollar contributed much of the material on the 'ms' macro package.  File: groff.info, Node: Invoking groff, Next: Tutorial for Macro Users, Prev: Introduction, Up: Top 2 Invoking 'groff' ****************** This chapter focuses on how to invoke the 'groff' front end. This front end takes care of the details of constructing the pipeline among the preprocessors, 'gtroff' and the postprocessor. It has become a tradition that GNU programs get the prefix 'g' to distinguish them from their original counterparts provided by the host (*note Environment::). Thus, for example, 'geqn' is GNU 'eqn'. On operating systems like GNU/Linux or the Hurd, which don't contain proprietary versions of 'troff', and on MS-DOS/MS-Windows, where 'troff' and associated programs are not available at all, this prefix is omitted since GNU 'troff' is the only incarnation of 'troff' used. Exception: 'groff' is never replaced by 'roff'. In this document, we consequently say 'gtroff' when talking about the GNU 'troff' program. All other implementations of 'troff' are called AT&T 'troff', which is the common origin of almost all 'troff' implementations(1) (*note Invoking groff-Footnote-1::) (with more or less compatible changes). Similarly, we say 'gpic', 'geqn', and so on. * Menu: * Groff Options:: * Environment:: * Macro Directories:: * Font Directories:: * Paper Format:: * Invocation Examples::  File: groff.info, Node: Invoking groff-Footnotes, Up: Invoking groff (1) Besides 'groff', 'neatroff' is an exception.  File: groff.info, Node: Groff Options, Next: Environment, Prev: Invoking groff, Up: Invoking groff 2.1 Options =========== 'groff' normally runs the 'gtroff' program and a postprocessor appropriate for the selected device. The default device is 'ps' (but it can be changed when 'groff' is configured and built). It can optionally preprocess with any of 'gpic', 'geqn', 'gtbl', 'ggrn', 'grap', 'gchem', 'grefer', 'gsoelim', or 'preconv'. This section documents only options to the 'groff' front end. Many of the arguments to 'groff' are passed on to 'gtroff'; therefore, those are also included. Arguments to preprocessors and output drivers can be found in the man pages 'gpic(1)', 'geqn(1)', 'gtbl(1)', 'ggrn(1)', 'grefer(1)', 'gchem(1)', 'gsoelim(1)', 'preconv(1)', 'grotty(1)', 'grops(1)', 'gropdf(1)', 'grohtml(1)', 'grodvi(1)', 'grolj4(1)', 'grolbp(1)', and 'gxditview(1)'. The command-line format for 'groff' is: groff [ -abceghijklpstvzCEGNRSUVXZ ] [ -dCS ] [ -DARG ] [ -fFAM ] [ -FDIR ] [ -IDIR ] [ -KARG ] [ -LARG ] [ -mNAME ] [ -MDIR ] [ -nNUM ] [ -oLIST ] [ -PARG ] [ -rCN ] [ -TDEV ] [ -wNAME ] [ -WNAME ] [ FILES... ] The command-line format for 'gtroff' is as follows. gtroff [ -abcivzCERU ] [ -dCS ] [ -fFAM ] [ -FDIR ] [ -mNAME ] [ -MDIR ] [ -nNUM ] [ -oLIST ] [ -rCN ] [ -TNAME ] [ -wNAME ] [ -WNAME ] [ FILES... ] Obviously, many of the options to 'groff' are actually passed on to 'gtroff'. Options without an argument can be grouped behind a single '-'. A filename of '-' denotes the standard input. Whitespace is permitted between an option and its argument. The 'grog' command can be used to guess the correct 'groff' command to format a file. See its man page 'grog(1)'; type 'man grog' at the command line to view it. 'groff''s command-line options are as follows. '-a' Generate a plain text approximation of the typeset output. The read-only register '.A' is set to 1. *Note Built-in Registers::. This option produces a sort of abstract preview of the formatted output. * Page breaks are marked by a phrase in angle brackets; for example, ''. * Lines are broken where they would be in the formatted output. * A horizontal motion of any size is represented as one space. Adjacent horizontal motions are not combined. Inter-sentence space nodes (those arising from the second argument to the 'ss' request) are not represented. * Vertical motions are not represented. * Special characters are rendered in angle brackets; for example, the default soft hyphen character appears as ''. The above description should not be considered a specification; the details of '-a' output are subject to change. '-b' Write a backtrace reporting the state of 'gtroff''s input parser to the standard error stream with each diagnostic message. The line numbers given in the backtrace might not always be correct, because 'gtroff''s idea of line numbers can be confused by requests that append to macros. '-c' Start with color output disabled. '-C' Enable AT&T 'troff' compatibility mode; implies '-c'. *Note Implementation Differences::, for the list of incompatibilities between 'groff' and AT&T 'troff'. '-dCTEXT' '-dSTRING=TEXT' Define 'roff' string C or STRING as T or TEXT. C must be one character; STRING can be of arbitrary length. Such string assignments happen before any macro file is loaded, including the startup file. Due to 'getopt_long' limitations, C cannot be, and STRING cannot contain, an equals sign, even though that is a valid character in a 'roff' identifier. '-DENC' Set fallback input encoding used by 'preconv' to ENC; implies '-k'. '-e' Run 'geqn' preprocessor. '-E' Inhibit 'gtroff' error messages. This option does _not_ suppress messages sent to the standard error stream by documents or macro packages using 'tm' or related requests. '-fFAM' Use FAM as the default font family. *Note Font Families::. '-FDIR' Search in directory 'DIR' for the selected output device's directory of device and font description files. See the description of 'GROFF_FONT_PATH' in *note Environment:: below for the default search locations and ordering. '-g' Run 'ggrn' preprocessor. '-G' Run 'grap' preprocessor; implies '-p'. '-h' Display a usage message and exit. '-i' Read the standard input after all the named input files have been processed. '-IDIR' Search the directory DIR for files named in several contexts; implies '-g' and '-s'. * 'gsoelim' replaces 'so' requests with the contents of their file name arguments. * 'gtroff' searches for files named as operands in its command line and as arguments to 'psbb', 'so', and 'soquiet' requests. * Output drivers may search for files; for instance, 'grops' looks for files named in '\X'ps: import ...'', '\X'ps: file ...'', and '\X'pdf: pdfpic ...'' device control escape sequences. This option may be specified more than once; the directories are searched in the order specified. If you want to search the current directory before others, add '-I .' at the desired place. The current working directory is otherwise searched last. '-I' works similarly to, and is named for, the "include" option of Unix C compilers. '-I' options are passed to 'gsoelim', 'gtroff', and output drivers; with the flag letter changed to '-M', they are also passed to 'ggrn'. '-j' Run 'gchem' preprocessor. Implies '-p'. '-k' Run 'preconv' preprocessor. Refer to its man page for its behavior if neither of 'groff''s '-K' or '-D' options is also specified. '-KENC' Set input encoding used by 'preconv' to ENC; implies '-k'. '-l' Send the output to a spooler for printing. The 'print' directive in the device description file specifies the default command to be used; see *note Device and Font Description Files::. See options '-L' and '-X'. '-LARG' Pass ARG to the print spooler program. If multiple ARGs are required, pass each with a separate '-L' option. 'groff' does not prefix an option dash to ARG before passing it to the spooler program. '-mNAME' Process the file 'NAME.tmac' prior to any input files. If not found, 'tmac.NAME' is attempted. NAME (in both arrangements) is presumed to be a macro file; see the description of 'GROFF_TMAC_PATH' in *note Environment:: below for the default search locations and ordering. This option and its argument are also passed to 'geqn', 'grap', and 'ggrn'. '-MDIR' Search directory 'DIR' for macro files; see the description of 'GROFF_TMAC_PATH' in *note Environment:: below for the default search locations and ordering. This option and its argument are also passed to 'geqn', 'grap', and 'ggrn'. '-nNUM' Number the first page NUM. '-N' Prohibit newlines between 'eqn' delimiters: pass '-N' to 'geqn'. '-oLIST' Output only pages in LIST, which is a comma-separated list of page ranges; 'N' means page N, 'M-N' means every page between M and N, '-N' means every page up to N, 'N-' means every page from N on. 'gtroff' stops processing and exits after formatting the last page enumerated in LIST. '-p' Run 'gpic' preprocessor. '-PARG' Pass ARG to the postprocessor. If multiple ARGs are required, pass each with a separate '-P' option. 'groff' does not prefix an option dash to ARG before passing it to the postprocessor. '-rCNUMERIC-EXPRESSION' '-rREGISTER=EXPR' Set 'roff' register C or REGISTER to the value NUMERIC-EXPRESSION (*note Numeric Expressions::). C must be one character; REGISTER can be of arbitrary length. Such register assignments happen before any macro file is loaded, including the startup file. Due to 'getopt_long' limitations, C cannot be, and REGISTER cannot contain, an equals sign, even though that is a valid character in a 'roff' identifier. '-R' Run 'grefer' preprocessor. No mechanism is provided for passing arguments to 'grefer' because most 'grefer' options have equivalent language elements that can be specified within the document. 'gtroff' also accepts a '-R' option, which is not accessible via 'groff'. This option prevents the loading of the 'troffrc' and 'troffrc-end' files. '-s' Run 'gsoelim' preprocessor. '-S' Operate in "safer" mode; see '-U' below for its opposite. For security reasons, safer mode is enabled by default. '-t' Run 'gtbl' preprocessor. '-TDEV' Direct 'gtroff' to format the input for the output device DEV. 'groff' then calls an output driver to convert 'gtroff''s output to a form appropriate for DEV. The following output devices are available. 'ps' For PostScript printers and previewers. 'pdf' For PDF viewers or printers. 'dvi' For TeX DVI format. 'X75' For a 75dpi X11 previewer. 'X75-12' For a 75dpi X11 previewer with a 12-point base font in the document. 'X100' For a 100dpi X11 previewer. 'X100-12' For a 100dpi X11 previewer with a 12-point base font in the document. 'ascii' For typewriter-like devices using the (7-bit) ASCII (ISO 646) character set. 'latin1' For typewriter-like devices that support the Latin-1 (ISO 8859-1) character set. 'utf8' For typewriter-like devices that use the Unicode (ISO 10646) character set with UTF-8 encoding. 'cp1047' For typewriter-like devices that use the EBCDIC encoding IBM code page 1047. 'lj4' For HP LaserJet4-compatible (or other PCL5-compatible) printers. 'lbp' For Canon CaPSL printers (LBP-4 and LBP-8 series laser printers). 'html' 'xhtml' To produce HTML and XHTML output, respectively. This driver consists of two parts, a preprocessor ('pre-grohtml') and a postprocessor ('post-grohtml'). The predefined GNU 'troff' string '.T' contains the name of the output device; the read-only register '.T' is set to 1 if this option is used (which is always true if 'groff' is used to call GNU 'troff'). *Note Built-in Registers::. The postprocessor to be used for a device is specified by the 'postpro' command in the device description file. (*Note Device and Font Description Files::.) This can be overridden with the '-X' option. '-U' Operate in "unsafe mode", which enables the 'open', 'opena', 'pi', 'pso', and 'sy' requests. These requests are disabled by default because they allow an untrusted input document to write to arbitrary file names and run arbitrary commands. This option also adds the current directory to the macro package search path; see the '-m' option above. '-U' is passed to 'gpic' and 'gtroff'. '-v' Write version information for 'groff' and all programs run by it to the standard output stream; that is, the given command line is processed in the usual way, passing '-v' to the formatter and any pre- or postprocessors invoked. '-V' Output the pipeline that would be run by 'groff' (as a wrapper program) to the standard output stream, but do not execute it. If given more than once, the pipeline is both written to the standard error stream and run. '-wCATEGORY' Enable warnings in CATEGORY. Categories are listed in *note Warnings::. '-WCATEGORY' Inhibit warnings in CATEGORY. Categories are listed in *note Warnings::. '-X' Use 'gxditview' instead of the usual postprocessor to (pre)view a document on an X11 display. Combining this option with '-Tps' uses the font metrics of the PostScript device, whereas the '-TX75' and '-TX100' options use the metrics of X11 fonts. '-z' Suppress formatted output from 'gtroff'. '-Z' Disable postprocessing. 'gtroff' output will appear on the standard output stream (unless suppressed with '-z'; see *note gtroff Output:: for a description of this format.  File: groff.info, Node: Environment, Next: Macro Directories, Prev: Groff Options, Up: Invoking groff 2.2 Environment =============== There are also several environment variables (of the operating system, not within 'gtroff') that can modify the behavior of 'groff'. 'GROFF_BIN_PATH' This search path, followed by 'PATH', is used for commands executed by 'groff'. 'GROFF_COMMAND_PREFIX' If this is set to X, then 'groff' runs 'Xtroff' instead of 'gtroff'. This also applies to 'tbl', 'pic', 'eqn', 'grn', 'chem', 'refer', and 'soelim'. It does not apply to 'grops', 'grodvi', 'grotty', 'pre-grohtml', 'post-grohtml', 'preconv', 'grolj4', 'gropdf', and 'gxditview'. The default command prefix is determined during the installation process. If a non-GNU 'troff' system is found, prefix 'g' is used, none otherwise. 'GROFF_ENCODING' The value of this variable is passed to the 'preconv' preprocessor's '-e' option to select the character encoding of input files. This variable's existence implies the 'groff' option '-k'. If set but empty, 'groff' calls 'preconv' without an '-e' option. 'groff''s '-K' option overrides 'GROFF_ENCODING'. See the 'preconv(7)' man page; type 'man preconv' at the command line to view it. 'GROFF_FONT_PATH' A list of directories in which to seek the selected output device's directory of device and font description files. GNU 'troff' will search directories given as arguments to any specified '-F' options before these, and a built-in list of directories after them. *Note Font Directories:: and the 'troff(1)' or 'gtroff(1)' man pages. 'GROFF_TMAC_PATH' A list of directories in which to seek macro files. GNU 'troff' will search directories given as arguments to any specified '-M' options before these, and a built-in list of directories after them. *Note Macro Directories:: and the 'troff(1)' or 'gtroff(1)' man pages. 'GROFF_TMPDIR' The directory in which 'groff' creates temporary files. If this is not set and 'TMPDIR' is set, temporary files are created in that directory. Otherwise temporary files are created in a system-dependent default directory (on Unix and GNU/Linux systems, this is usually '/tmp'). 'grops', 'grefer', 'pre-grohtml', and 'post-grohtml' can create temporary files in this directory. 'GROFF_TYPESETTER' Sets the default output device. If empty or not set, a build-time default (often 'ps') is used. The '-TDEV' option overrides 'GROFF_TYPESETTER'. 'SOURCE_DATE_EPOCH' A timestamp (expressed as seconds since the Unix epoch) to use as the output creation timestamp in place of the current time. The time is converted to human-readable form using 'localtime(3)' when the formatter starts up and stored in registers usable by documents and macro packages (*note Built-in Registers::). 'TZ' The time zone to use when converting the current time (or value of 'SOURCE_DATE_EPOCH') to human-readable form; see 'tzset(3)'. MS-DOS and MS-Windows ports of 'groff' use semicolons, rather than colons, to separate the directories in the lists described above.  File: groff.info, Node: Macro Directories, Next: Font Directories, Prev: Environment, Up: Invoking groff 2.3 Macro Directories ===================== A macro file must have a name in the form 'NAME.tmac' or 'tmac.NAME' and be placed in a "tmac directory" to be found by the '-mNAME' command-line option.(1) (*note Macro Directories-Footnote-1::) Together, these directories constitute the "tmac path". Each directory is searched in the following order until the desired macro file is found or the list is exhausted. * Directories specified with GNU 'troff''s or 'groff''s '-M' command-line option. * Directories listed in the 'GROFF_TMAC_PATH' environment variable. * The current working directory (only if in unsafe mode using the '-U' command-line option). * The user's home directory, 'HOME'. * A platform-dependent directory, a site-local (platform-independent) directory, and the main tmac directory. The locations corresponding to your installation are listed in section "Environment" of 'gtroff(1)'. If not otherwise configured, they are as follows. /usr/local/lib/groff/site-tmac /usr/local/share/groff/site-tmac /usr/local/share/groff/1.23.0/tmac The foregoing assumes that the version of 'groff' is 1.23.0, and that the installation prefix was '/usr/local'. It is possible to fine-tune these locations during the source configuration process.  File: groff.info, Node: Macro Directories-Footnotes, Up: Macro Directories (1) The 'mso' request does not have these limitations. *Note I/O::.  File: groff.info, Node: Font Directories, Next: Paper Format, Prev: Macro Directories, Up: Invoking groff 2.4 Font Directories ==================== 'groff' enforces few restrictions on how font description files are named. For its family/style mechanism to work (*note Font Families::), the names of fonts within a family should start with the family name, followed by the style. For example, the Times family uses 'T' for the family name and 'R', 'B', 'I', and 'BI' to indicate the styles 'roman', 'bold', 'italic', and 'bold italic', respectively. Thus the final font names are 'TR', 'TB', 'TI', and 'TBI'. Font description files are kept in "font directories", which together constitute the "font path". The search procedure always appends the directory 'dev'NAME, where NAME is the name of the output device. Assuming TeX DVI output, and '/foo/bar' as a font directory, the font description files for 'grodvi' must be in '/foo/bar/devdvi'. Each directory in the font path is searched in the following order until the desired font description file is found or the list is exhausted. * Directories specified with GNU 'troff''s or 'groff''s '-f' command-line option. All output drivers (and some preprocessors) support this option as well, because they require information about the glyphs to be rendered in the document. * Directories listed in the 'GROFF_FONT_PATH' environment variable. * A site-local directory and the main font description directory. The locations corresponding to your installation are listed in section "Environment" of 'gtroff(1)'. If not otherwise configured, they are as follows. /usr/local/share/groff/site-font /usr/local/share/groff/1.23.0/font The foregoing assumes that the version of 'groff' is 1.23.0, and that the installation prefix was '/usr/local'. It is possible to fine-tune these locations during the source configuration process.  File: groff.info, Node: Paper Format, Next: Invocation Examples, Prev: Font Directories, Up: Invoking groff 2.5 Paper Format ================ In 'groff', the page dimensions for the formatter GNU 'troff' and for output devices are handled separately. *Note Page Layout::, for vertical manipulation of the page size, and *Note Line Layout::, for horizontal changes. The 'papersize' macro package, normally loaded by 'troffrc' at startup, provides an interface for configuring page dimensions by convenient names, like 'letter' or 'a4'; see 'groff_tmac(5)'. The default used by the formatter depends on its build configuration, but is usually one of the foregoing, as geographically appropriate. It is up to each macro package to respect the page dimensions configured in this way. For each output device, the size of the output medium can be set in its 'DESC' file. Most output drivers also recognize a command-line option '-p' to override the default dimensions and an option '-l' to use landscape orientation. *Note DESC File Format::, for a description of the 'papersize' keyword, which takes an argument of the same form as '-p'. The output driver's man page, such as 'grops(1)', may also be helpful. 'groff' uses the command-line option '-P' to pass options to postprocessors; for example, use the following for PostScript output on A4 paper in landscape orientation. groff -Tps -dpaper=a4l -P-pa4 -P-l -ms foo.ms > foo.ps  File: groff.info, Node: Invocation Examples, Prev: Paper Format, Up: Invoking groff 2.6 Invocation Examples ======================= 'roff' systems are best known for formatting man pages. Once a 'man' librarian program has located a man page, it may execute a 'groff' command much like the following. groff -t -man -Tutf8 /usr/share/man/man1/groff.1 The librarian will also pipe the output through a pager, which might not interpret the SGR terminal escape sequences 'groff' emits for boldface, underlining, or italics; see the 'grotty(1)' man page for a discussion. To process a 'roff' input file using the preprocessors 'gtbl' and 'gpic' and the 'me' macro package in the way to which AT&T 'troff' users were accustomed, one would type (or script) a pipeline. gpic foo.me | gtbl | gtroff -me -Tutf8 | grotty Using 'groff', this pipe can be shortened to an equivalent command. groff -p -t -me -T utf8 foo.me An even easier way to do this is to use 'grog' to guess the preprocessor and macro options and execute the result by using the command substitution feature of the shell. $(grog -Tutf8 foo.me) Each command-line option to a postprocessor must be specified with any required leading dashes '-' because 'groff' passes the arguments as-is to the postprocessor; this permits arbitrary arguments to be transmitted. For example, to pass a title to the 'gxditview' postprocessor, the shell commands groff -X -P -title -P 'trial run' mydoc.t and groff -X -Z mydoc.t | gxditview -title 'trial run' - are equivalent.  File: groff.info, Node: Tutorial for Macro Users, Next: Major Macro Packages, Prev: Invoking groff, Up: Top 3 Tutorial for Macro Users ************************** Most users of the 'roff' language employ a macro package to format their documents. Successful macro packages ease the composition process; their users need not have mastered the full formatting language, nor understand features like diversions, traps, and environments. This chapter aims to familiarize you with basic concepts and mechanisms common to many macro packages (like "displays"). If you prefer a meticulous and comprehensive presentation, try *note GNU troff Reference:: instead. * Menu: * Basics:: * Common Features::  File: groff.info, Node: Basics, Next: Common Features, Prev: Tutorial for Macro Users, Up: Tutorial for Macro Users 3.1 Basics ========== Let us first survey some basic concepts necessary to use a macro package fruitfully.(1) (*note Basics-Footnote-1::) References are made throughout to more detailed information. GNU 'troff' reads an input file prepared by the user and outputs a formatted document suitable for publication or framing. The input consists of text, or words to be printed, and embedded commands (requests and escape sequences), which tell GNU 'troff' how to format the output. *Note Formatter Instructions::. The word argument is used in this chapter to mean a word or number that appears on the same line as a request, and which modifies the meaning of that request. For example, the request .sp spaces one line, but .sp 4 spaces four lines. The number 4 is an argument to the 'sp' request, which says to space four lines instead of one. Arguments are separated from the request and from each other by spaces (_not_ tabs). *Note Invoking Requests::. The primary function of GNU 'troff' is to collect words from input lines, fill output lines with those words, adjust the line to the right-hand margin by widening spaces, and output the result. For example, the input: Now is the time for all good men to come to the aid of their party. Four score and seven years ago, etc. is read, packed onto output lines, and justified to produce: => Now is the time for all good men to come to the aid of => their party. Four score and seven years ago, etc. Sometimes a new output line should be started even though the current line is not yet full--for example, at the end of a paragraph. To do this it is possible to force a break, starting a new output line. Some requests cause a break automatically, as do (normally) blank input lines and input lines beginning with a space or tab. Not all input lines are text lines--words to be formatted. Some are control lines that tell a macro package (or GNU 'troff' directly) how to format the text. Control lines start with a dot ('.') or an apostrophe (''') as the first character, and can be followed by a macro call. The formatter also does more complex things, such as automatically numbering pages, skipping over page boundaries, putting footnotes in the correct place, and so forth. Here are a few hints for preparing text for input to GNU 'troff'. * First, keep the input lines short. Short input lines are easier to edit, and GNU 'troff' packs words onto longer lines anyhow. * In keeping with this, it is helpful to begin a new line after every comma or phrase, since common corrections are to add or delete sentences or phrases. * End each sentence with two spaces--or better, start each sentence on a new line. GNU 'troff' recognizes characters that usually end a sentence, and inserts inter-sentence space accordingly. * Do not hyphenate words at the end of lines--GNU 'troff' is smart enough to hyphenate words as needed, but is not smart enough to take hyphens out and join a word back together. Also, words such as "mother-in-law" should not be broken over a line, since then a space can occur where not wanted, such as "mother- in-law". We offer further advice in *note Input Conventions::. GNU 'troff' permits alteration of the distance between lines of text. This is termed vertical spacing and is expressed in the same units as the type size--the point. The default is 10-point type on 12-point spacing. To get double-spaced text you would set the vertical spacing to 24 points. Some, but not all, macro packages expose a macro or register to configure the vertical spacing. A number of requests allow you to change the way the output is arranged on the page, sometimes called the layout of the output page. Most macro packages don't supply macros for performing these (at least not without performing other actions besides), as they are such basic operations. The macro packages for writing man pages, 'man' and 'mdoc', don't encourage explicit use of these requests at all. The request '.sp N' leaves N lines of blank space. N can be omitted (skipping a single line) or can be of the form Ni (for N inches) or Nc (for N centimeters). For example, the input: .sp 1.5i My thoughts on the subject .sp leaves one and a half inches of space, followed by the line "My thoughts on the subject", followed by a single blank line (more measurement units are available; see *note Measurements::). If you seek precision in spacing, be advised when using a macro package that it might not honor 'sp' requests as you expect; it can use a formatter feature called no-space mode to prevent excess space from accumulating. Macro packages typically offer registers to control spacing between paragraphs, before section headings, and around displays (discussed below); use these facilities preferentially. *Note Manipulating Spacing::. Text lines can be centered by using the 'ce' request. The line after 'ce' is centered (horizontally) on the page. To center more than one line, use '.ce N' (where N is the number of lines to center), followed by the N lines. To center many lines without counting them, type: .ce 1000 lines to center .ce 0 The '.ce 0' request tells GNU 'troff' to center zero more lines, in other words, stop centering. GNU 'troff' also offers the 'rj' request for right-aligning text. It works analogously to 'ce' and is convenient for setting epigraphs. The 'bp' request starts a new page; this necessarily implies an ordinary (line) break. All of these requests cause a break; that is, they always start a new line. To start a new line without performing any other action, use 'br'. If you invoke them with the apostrophe ''', the no-break control character, the (initial) break they normally perform is suppressed. ''br' does nothing.  File: groff.info, Node: Basics-Footnotes, Up: Basics (1) The remainder of this chapter is based on 'Writing Papers with nroff using -me' by Eric P. Allman, which is distributed with 'groff' as 'meintro.me'.  File: groff.info, Node: Common Features, Prev: Basics, Up: Tutorial for Macro Users 3.2 Common Features =================== GNU 'troff' provides low-level operations for formatting a document. Many routine operations are undertaken in nearly all documents that require a series of such primitive operations to be performed. These common tasks are grouped into macros, which are then collected into a macro package. Macro packages come in two varieties: "major" or "full-service" ones that manage page layout, and "minor" or "auxiliary" ones that do not, instead fulfilling narrow, specific tasks. Find a list in the 'groff_tmac(5)' man page. Type 'man groff_tmac' at the command line to view it. We survey several capabilities of full-service macro package below. Each package employs its own macros to exercise them. For details, consult its man page or, for 'ms', see *note ms::. * Menu: * Paragraphs:: * Sections and Chapters:: * Headers and Footers:: * Page Layout Adjustment:: * Displays and Keeps:: * Footnotes and Endnotes:: * Table of Contents:: * Indexing:: * Document Formats:: * Columnation:: * Font and Size Changes:: * Predefined Text:: * Preprocessor Support:: * Configuration and Customization::  File: groff.info, Node: Paragraphs, Next: Sections and Chapters, Prev: Common Features, Up: Common Features 3.2.1 Paragraphs ---------------- Paragraphs can be separated and indented in various ways. Some start with a blank line and have a first-line indentation, like most of the ones in this manual. Block paragraphs omit the indentation. => Some men look at constitutions with sanctimonious => reverence, and deem them like the ark of the => covenant, too sacred to be touched. We also frequently encounter tagged paragraphs, which begin with a tag or label at the left margin and indent the remaining text. => one This is the first paragraph. Notice how the => first line of the resulting paragraph lines => up with the other lines in the paragraph. If the tag is too wide for the indentation, the line is broken. => longlabel => The label does not align with the subsequent => lines, but they align with each other. A variation of the tagged paragraph is the itemized or enumerated paragraph, which might use punctuation or a digit for a tag, respectively. These are frequently used to construct lists. => o This list item starts with a bullet. When => producing output for a device using the ASCII => character set, an 'o' is formatted instead. Often, use of the same macro without a tag continues such a discussion. => -xyz This option is recognized but ignored. => => It had a security hole that we don't discuss.  File: groff.info, Node: Sections and Chapters, Next: Headers and Footers, Prev: Paragraphs, Up: Common Features 3.2.2 Sections and Chapters --------------------------- The simplest kind of section heading is unnumbered, set in a bold or italic style, and occupies a line by itself. Others possess automatically numbered multi-level headings and/or different typeface styles or sizes at different levels. More sophisticated macro packages supply macros for designating chapters and appendices.  File: groff.info, Node: Headers and Footers, Next: Page Layout Adjustment, Prev: Sections and Chapters, Up: Common Features 3.2.3 Headers and Footers ------------------------- Headers and footers occupy the top and bottom of each page, respectively, and contain data like the page number and the article or chapter title. Their appearance is not affected by the running text. Some packages allow for different titles on even- and odd-numbered pages (for printed, bound material). Headers and footers are together called titles, and comprise three parts: left-aligned, centered, and right-aligned. A '%' character appearing anywhere in a title is automatically replaced by the page number. *Note Page Layout::.  File: groff.info, Node: Page Layout Adjustment, Next: Displays and Keeps, Prev: Headers and Footers, Up: Common Features 3.2.4 Page Layout ----------------- Most macro packages let the user specify the size of the page margins. The top and bottom margins are typically handled differently than the left and right margins; the latter two are derived from the page offset, indentation, and line length. *Note Line Layout::. Commonly, packages support registers to tune these values.  File: groff.info, Node: Displays and Keeps, Next: Footnotes and Endnotes, Prev: Page Layout Adjustment, Up: Common Features 3.2.5 Displays and Keeps ------------------------ Displays are sections of text set off from the surrounding material (typically paragraphs), often differing in indentation, and/or spacing. Tables, block quotations, and figures are displayed. Equations and code examples, when not much shorter than an output line, often are. Lists may or may not be. Packages for setting man pages support example displays but not keeps. A keep is a group of output lines, often a display, that is formatted on a single page if possible; it causes a page break to happen early so as to not interrupt the kept material. Floating keeps can move, or "float", relative to the text around them in the input. They are useful for displays that are captioned and referred to by name, as with "See figure 3". Depending on the package, a floating keep appears at the bottom of the current page if it fits, and at the top of the next otherwise. Alternatively, floating keeps might be deferred to the end of a section. Using a floating keep can avoid the large vertical spaces that may precede a tall keep of the ordinary sort when it won't fit on the page.  File: groff.info, Node: Footnotes and Endnotes, Next: Table of Contents, Prev: Displays and Keeps, Up: Common Features 3.2.6 Footnotes and Endnotes ---------------------------- Footnotes and endnotes are forms of delayed formatting. They are recorded at their points of relevance in the input, but not formatted there. Instead, a mark cues the reader to check the "foot", or bottom, of the current page, or in the case of endnotes, an annotation list later in the document. Macro packages that support these features also supply a means of automatically numbering either type of annotation.  File: groff.info, Node: Table of Contents, Next: Indexing, Prev: Footnotes and Endnotes, Up: Common Features 3.2.7 Table of Contents ----------------------- A package may handle a table of contents by directing section heading macros to save section heading text and the page number where it occurs for use in a later entry for a table of contents. It writes the collected entries at the end of the document, once all are known, upon request. A row of dots (a leader) bridges the text on the left with its location on the right. Other collections might work in this manner, providing lists of figures or tables. A table of contents is often found at the end of a GNU 'troff' document because the formatter processes the document in a single pass. The 'gropdf' output driver supports a PDF feature that relocates pages at the time the document is rendered; see the 'gropdf(1)' man page. Type 'man gropdf' at the command line to view it.  File: groff.info, Node: Indexing, Next: Document Formats, Prev: Table of Contents, Up: Common Features 3.2.8 Indexing -------------- An index is similar to a table of contents, in that entry labels and locations must be collected, but poses a greater challenge because it needs to be sorted before it is output. Here, processing the document in multiple passes is inescapable, and tools like the 'makeindex' program are necessary.  File: groff.info, Node: Document Formats, Next: Columnation, Prev: Indexing, Up: Common Features 3.2.9 Document Formats ---------------------- Some macro packages supply stock configurations of certain documents, like business letters and memoranda. These often also have provision for a cover sheet, which may be rigid in its format. With these features, it is even more important to use the package's macros in preference to the formatter requests presented earlier, where possible.  File: groff.info, Node: Columnation, Next: Font and Size Changes, Prev: Document Formats, Up: Common Features 3.2.10 Columnation ------------------ Macro packages apart from 'man' and 'mdoc' for man page formatting offer a facility for setting multiple columns on the page.  File: groff.info, Node: Font and Size Changes, Next: Predefined Text, Prev: Columnation, Up: Common Features 3.2.11 Font and Size Changes ---------------------------- The formatter's requests and escape sequences for setting the typeface and size are not always intuitive, so all macro packages provide macros to make these operations simpler. They also make it more convenient to change typefaces in the middle of a word and can handle italic corrections automatically. *Note Italic Corrections::.  File: groff.info, Node: Predefined Text, Next: Preprocessor Support, Prev: Font and Size Changes, Up: Common Features 3.2.12 Predefined Text ---------------------- Most macro packages supply predefined strings to set prepared text like the date, or to perform operations like super- and subscripting.  File: groff.info, Node: Preprocessor Support, Next: Configuration and Customization, Prev: Predefined Text, Up: Common Features 3.2.13 Preprocessor Support --------------------------- All macro packages provide support for various preprocessors and may extend their functionality by defining macros to set their contents in displays. Examples include 'TS' and 'TE' for 'gtbl', 'EQ' and 'EN' for 'geqn', and 'PS' and 'PE' for 'gpic'.  File: groff.info, Node: Configuration and Customization, Prev: Preprocessor Support, Up: Common Features 3.2.14 Configuration and Customization -------------------------------------- Packages provide means of customizing many of the details of how the package behaves. These range from setting the default type size to changing the appearance of section headers.  File: groff.info, Node: Major Macro Packages, Next: GNU troff Reference, Prev: Tutorial for Macro Users, Up: Top 4 Macro Packages **************** This chapter surveys the "major" macro packages that come with 'groff'. One, 'ms', is presented in detail. Major macro packages are also sometimes described as "full-service" due to the breadth of features they provide and because more than one cannot be used by the same document; for example groff -m man foo.man -m ms bar.doc doesn't work. Option arguments are processed before non-option arguments; the above (failing) sample is thus reordered to groff -m man -m ms foo.man bar.doc Many auxiliary, or "minor", macro packages are also available. They may in general be used with any full-service macro package and handle a variety of tasks from character encoding selection, to language localization, to inlining of raster images. See the 'groff_tmac(5)' man page for a list. Type 'man groff_tmac' at the command line to view it. * Menu: * man:: * mdoc:: * me:: * mm:: * mom:: * ms::  File: groff.info, Node: man, Next: mdoc, Prev: Major Macro Packages, Up: Major Macro Packages 4.1 'man' ========= The 'man' macro package is the most widely used and probably the most important ever developed for 'troff'. It is easy to use, and a vast majority of manual pages ("man pages") are written in it. 'groff''s implementation is documented in the 'groff_man(7)' man page. Type 'man groff_man' at the command line to view it. * Menu: * Optional man extensions::  File: groff.info, Node: Optional man extensions, Up: man 4.1.1 Optional 'man' extensions ------------------------------- Use the file 'man.local' for local extensions to the 'man' macros or for style changes. Custom headers and footers .......................... In 'groff' versions 1.18.2 and later, you can specify custom headers and footers by redefining the following macros in 'man.local'. -- Macro: .PT Control the content of the headers. Normally, the header prints the command name and section number on either side, and the optional fifth argument to 'TH' in the center. -- Macro: .BT Control the content of the footers. Normally, the footer prints the page number and the third and fourth arguments to 'TH'. Use the 'FT' register to specify the footer position. The default is -0.5i. Ultrix-specific man macros .......................... The 'groff' source distribution includes a file named 'man.ultrix', containing macros compatible with the Ultrix variant of 'man'. Copy this file into 'man.local' (or use the 'mso' request to load it) to enable the following macros. -- Macro: .CT key Print ''. -- Macro: .CW Print subsequent text using a "constant-width" (monospaced) typeface (Courier roman). -- Macro: .Ds Begin a non-filled display. -- Macro: .De End a non-filled display started with 'Ds'. -- Macro: .EX [indent] Begin a non-filled display using a monospaced typeface (Courier roman). Use the optional INDENT argument to indent the display. -- Macro: .EE End a non-filled display started with 'EX'. -- Macro: .G [text] Set TEXT in Helvetica. If no text is present on the line where the macro is called, then the text of the next line appears in Helvetica. -- Macro: .GL [text] Set TEXT in Helvetica oblique. If no text is present on the line where the macro is called, then the text of the next line appears in Helvetica Oblique. -- Macro: .HB [text] Set TEXT in Helvetica bold. If no text is present on the line where the macro is called, then all text up to the next 'HB' appears in Helvetica bold. -- Macro: .TB [text] Identical to 'HB'. -- Macro: .MS title sect [punct] Set a man page reference in Ultrix format. The TITLE is in Courier instead of italic. Optional punctuation follows the section number without an intervening space. -- Macro: .NT [C] [title] Begin a note. Print the optional title, or the word "Note", centered on the page. Text following the macro makes up the body of the note, and is indented on both sides. If the first argument is 'C', the body of the note is printed centered (the second argument replaces the word "Note" if specified). -- Macro: .NE End a note begun with 'NT'. -- Macro: .PN path [punct] Set the path name in a monospaced typeface (Courier roman), followed by optional punctuation. -- Macro: .Pn [punct] path [punct] If called with two arguments, identical to 'PN'. If called with three arguments, set the second argument in a monospaced typeface (Courier roman), bracketed by the first and third arguments in the current font. -- Macro: .R Switch to roman font and turn off any underlining in effect. -- Macro: .RN Print the string ''. -- Macro: .VS [4] Start printing a change bar in the margin if the number '4' is specified. Otherwise, this macro does nothing. -- Macro: .VE End printing the change bar begun by 'VS'. Simple example .............. The following example 'man.local' file alters the 'SH' macro to add some extra vertical space before printing the heading. Headings are printed in Helvetica bold. .\" Make the heading fonts Helvetica .ds HF HB . .\" Put more space in front of headings. .rn SH SH-orig .de SH . if t .sp (u;\\n[PD]*2) . SH-orig \\$* ..  File: groff.info, Node: mdoc, Next: me, Prev: man, Up: Major Macro Packages 4.2 'mdoc' ========== 'groff''s implementation of the BSD 'doc' package for man pages is documented in the 'groff_mdoc(7)' man page. Type 'man groff_mdoc' at the command line to view it.  File: groff.info, Node: me, Next: mm, Prev: mdoc, Up: Major Macro Packages 4.3 'me' ======== 'groff''s implementation of the BSD 'me' macro package is documented using itself. A tutorial, 'meintro.me', and reference, 'meref.me', are available in 'groff''s documentation directory. A 'groff_me(7)' man page is also available and identifies the installation path for these documents. Type 'man groff_me' at the command line to view it. A French translation of the tutorial is available as 'meintro_fr.me' and installed parallel to the English version.  File: groff.info, Node: mm, Next: mom, Prev: me, Up: Major Macro Packages 4.4 'mm' ======== 'groff''s implementation of the AT&T memorandum macro package is documented in the 'groff_mm(7)' man page. Type 'man groff_mm' at the command line) to view it. A Swedish localization of 'mm' is also available; see 'groff_mmse(7)'.  File: groff.info, Node: mom, Next: ms, Prev: mm, Up: Major Macro Packages 4.5 'mom' ========= The main documentation files for the 'mom' macros are in HTML format. Additional, useful documentation is in PDF format. See the 'groff(1)' man page, section "Installation Directories", for their location. * 'toc.html' Entry point to the full mom manual. * 'macrolist.html' Hyperlinked index of macros with brief descriptions, arranged by category. * 'mom-pdf.pdf' PDF features and usage. The mom macros are in active development between 'groff' releases. The most recent version, along with up-to-date documentation, is available at . The 'groff_mom(7)' man page (type 'man groff_mom' at the command line) contains a partial list of available macros, however their usage is best understood by consulting the HTML documentation.  File: groff.info, Node: ms, Prev: mom, Up: Major Macro Packages 4.6 'ms' ======== The 'ms' ("manuscript") package is suitable for the preparation of letters, memoranda, reports, and books. These 'groff' macros feature cover page and table of contents generation, automatically numbered headings, several paragraph styles, a variety of text styling options, footnotes, and multi-column page layouts. 'ms' supports the 'tbl', 'eqn', 'pic', and 'refer' preprocessors for inclusion of tables, mathematical equations, diagrams, and standardized bibliographic citations. This implementation is mostly compatible with the documented interface and behavior of AT&T Unix Version 7 'ms'. Many extensions from 4.2BSD (Berkeley) and Tenth Edition Research Unix have been recreated. * Menu: * ms Introduction:: * ms Document Structure:: * ms Document Control Settings:: * ms Document Description Macros:: * ms Body Text:: * ms Page Layout:: * Differences from AT&T ms:: * ms Legacy Features:: * ms Naming Conventions::  File: groff.info, Node: ms Introduction, Next: ms Document Structure, Prev: ms, Up: ms 4.6.1 Introduction ------------------ The 'ms' macros are the oldest surviving package for 'roff' systems.(1) (*note ms Introduction-Footnote-1::) While the 'man' package was designed for brief reference documents, the 'ms' macros are also suitable for longer works intended for printing and possible publication. * Menu: * ms basic information::  File: groff.info, Node: ms Introduction-Footnotes, Up: ms Introduction (1) While manual _pages_ are older, early ones used macros supplanted by the 'man' package of Seventh Edition Unix (1979). 'ms' shipped with Sixth Edition (1975) and was documented by Mike Lesk in a Bell Labs internal memorandum.  File: groff.info, Node: ms basic information, Next: ms Document Structure, Prev: ms Introduction, Up: ms Introduction 4.6.1.1 Basic information ......................... 'ms' documents are plain text files; prepare them with your preferred text editor. If you're in a hurry to start, know that 'ms' needs one of its macros called at the beginning of a document so that it can initialize. A "macro" is a formatting instruction to 'ms'. Put a macro call on a line by itself. Use '.PP' if you want your paragraph's first line to be indented, or '.LP' if you don't. After that, start typing normally. It is a good practice to start each sentence on a new line, or to put two spaces after sentence-ending punctuation, so that the formatter knows where the sentence boundaries are. You can separate paragraphs with further paragraphing macros, or with blank lines, and you can indent with tabs. When you need one of the features mentioned earlier (*note ms::), return to this part of the manual. Format the document with the 'groff' command. 'nroff' can be useful for previewing. $ editor radical.ms $ nroff -ww -z -ms radical.ms # check for errors $ nroff -ms radical.ms | less -R $ groff -T ps -ms radical.ms > radical.ps $ see radical.ps Our 'radical.ms' document might look like this. .LP Radical novelties are so disturbing that they tend to be suppressed or ignored, to the extent that even the possibility of their existence in general is more often denied than admitted. ->That's what Dijkstra said, anyway. 'ms' exposes many aspects of document layout to user control via 'groff''s "registers" and "strings", which store numbers and text, respectively. Measurements in 'groff' are expressed with a suffix called a "scaling unit". 'i' inches 'c' centimeters 'p' points (1/72 inch) 'P' picas (1/6 inch) 'v' vees; current vertical spacing 'm' ems; width of an "M" in the current font 'n' ens; one-half em Set registers with the 'nr' request and strings with the 'ds' request. "Requests" are like macro calls; they go on lines by themselves and start with the "control character", a dot ('.'). The difference is that they directly instruct the formatter program, rather than the macro package. We'll discuss a few as applicable. It is wise to specify a scaling unit when setting any register that represents a length, size, or distance. .nr PS 10.5p \" Use 10.5-point type. .ds FAM P \" Use Palatino font family. In the foregoing, we see that '\"' begins a comment. This is an example of an "escape sequence", the other kind of formatting instruction. Escape sequences can appear anywhere. They begin with the escape character ('\') and are followed by at least one more character. 'ms' documents tend to use only a few of 'groff''s many requests and escape sequences; see *note Request Index:: and *note Escape Sequence Index:: or the 'groff(7)' man page for complete lists. '\"' Begin comment; ignore remainder of line. '\n[REG]' Interpolate value of register REG. '\*[STR]' Interpolate contents of string STR. '\*S' abbreviation of '\*[S]'; the name S must be only one character '\[CHAR]' Interpolate glyph of special character named CHAR. '\&' dummy character '\~' Insert an unbreakable space that is adjustable like a normal space. '\|' Move horizontally by one-sixth em ("thin space"). Prefix any words that start with a dot '.' or neutral apostrophe ''' with '\&' if they are at the beginning of an input line (or might become that way in editing) to prevent them from being interpreted as macro calls or requests. Suffix '.', '?', and '!' with '\&' when needed to cancel end-of-sentence detection. My exposure was \&.5 to \&.6 Sv of neutrons, said Dr.\& Wallace after the criticality incident.  File: groff.info, Node: ms Document Structure, Next: ms Document Control Settings, Prev: ms Introduction, Up: ms 4.6.2 Document Structure ------------------------ The 'ms' macro package expects a certain amount of structure: a well-formed document contains at least one paragraphing or heading macro call. Longer documents have a structure as follows. *Document type* Calling the 'RP' macro at the beginning of your document puts the document description (see below) on a cover page. Otherwise, 'ms' places the information (if any) on the first page, followed immediately by the body text. Some document types found in other 'ms' implementations are specific to AT&T or Berkeley, and are not supported by 'groff' 'ms'. *Format and layout* By setting registers and strings, you can configure your document's typeface, margins, spacing, headers and footers, and footnote arrangement. *Note ms Document Control Settings::. *Document description* A document description consists of any of: a title, one or more authors' names and affiliated institutions, an abstract, and a date or other identifier. *Note ms Document Description Macros::. *Body text* The main matter of your document follows its description (if any). 'ms' supports highly structured text consisting of paragraphs interspersed with multi-level headings (chapters, sections, subsections, and so forth) and augmented by lists, footnotes, tables, diagrams, and similar material. *Note ms Body Text::. *Tables of contents* Macros enable the collection of entries for a table of contents (or index) as the material they discuss appears in the document. You then call a macro to emit the table of contents at the end of your document. The table of contents must necessarily follow the rest of the text since GNU 'troff' is a single-pass formatter; it thus cannot determine the page number of a division of the text until it has been set and output. Since 'ms' was designed for the production of hard copy, the traditional procedure was to manually relocate the pages containing the table of contents between the cover page and the body text. Today, page resequencing is more often done in the digital domain. An index works similarly, but because it typically needs to be sorted after collection, its preparation requires separate processing.  File: groff.info, Node: ms Document Control Settings, Next: ms Document Description Macros, Prev: ms Document Structure, Up: ms 4.6.3 Document Control Settings ------------------------------- 'ms' exposes many aspects of document layout to user control via 'groff' requests. To use them, you must understand how to define registers and strings. -- Request: .nr reg value Set register REG to VALUE. If REG doesn't exist, GNU 'troff' creates it. -- Request: .ds name contents Set string NAME to CONTENTS. A list of document control registers and strings follows. For any parameter whose default is unsatisfactory, define its register or string before calling any 'ms' macro other than 'RP'. Margin settings ............... -- Register: \n[PO] Defines the page offset (i.e., the left margin). Effective: next page. Default: Varies by output device and paper format; 1i is used for typesetters using U.S. letter paper, and zero for terminals. *Note Paper Format::. -- Register: \n[LL] Defines the line length (i.e., the width of the body text). Effective: next paragraph. Default: Varies by output device and paper format; 6.5i is used for typesetters using U.S. letter paper (*note Paper Format::) and 65n on terminals. -- Register: \n[LT] Defines the title line length (i.e., the header and footer width). This is usually the same as 'LL', but need not be. Effective: next paragraph. Default: Varies by output device and paper format; 6.5i is used for typesetters using U.S. letter paper (*note Paper Format::) and 65n on terminals. -- Register: \n[HM] Defines the header margin height at the top of the page. Effective: next page. Default: 1i. -- Register: \n[FM] Defines the footer margin height at the bottom of the page. Effective: next page. Default: 1i. Titles (headers, footers) ......................... -- String: \*[LH] Defines the text displayed in the left header position. Effective: next header. Default: empty. -- String: \*[CH] Defines the text displayed in the center header position. Effective: next header. Default: '-\n[%]-'. -- String: \*[RH] Defines the text displayed in the right header position. Effective: next header. Default: empty. -- String: \*[LF] Defines the text displayed in the left footer position. Effective: next footer. Default: empty. -- String: \*[CF] Defines the text displayed in the center footer position. Effective: next footer. Default: empty. -- String: \*[RF] Defines the text displayed in the right footer position. Effective: next footer. Default: empty. Text settings ............. -- Register: \n[PS] Defines the type size of the body text. Effective: next paragraph. Default: 10p. -- Register: \n[VS] Defines the vertical spacing (type size plus leading). Effective: next paragraph. Default: 12p. -- Register: \n[HY] Defines the automatic hyphenation mode used with the 'hy' request. Setting 'HY' to 0 is equivalent to using the 'nh' request. This is a Tenth Edition Research Unix extension. Effective: next paragraph. Default: 6. -- String: \*[FAM] Defines the font family used to typeset the document. This is a GNU extension. Effective: next paragraph. Default: defined by the output device; often 'T' (*note ms Body Text::) Paragraph settings .................. -- Register: \n[PI] Defines the indentation amount used by the 'PP', 'IP' (unless overridden by an optional argument), 'XP', and 'RS' macros. Effective: next paragraph. Default: 5n. -- Register: \n[PD] Defines the space between paragraphs. Effective: next paragraph. Default: 0.3v (1v on low-resolution devices). -- Register: \n[QI] Defines the indentation amount used on both sides of a paragraph set with the 'QP' or between the 'QS' and 'QE' macros. Effective: next paragraph. Default: 5n. -- Register: \n[PORPHANS] Defines the minimum number of initial lines of any paragraph that must be kept together to avoid isolated lines at the bottom of a page. If a new paragraph is started close to the bottom of a page, and there is insufficient space to accommodate 'PORPHANS' lines before an automatic page break, then a page break is forced before the start of the paragraph. This is a GNU extension. Effective: next paragraph. Default: 1. Heading settings ................ -- Register: \n[PSINCR] Defines an increment in type size to be applied to a heading at a lesser depth than that specified in 'GROWPS'. The value of 'PSINCR' should be specified in points with the p scaling unit and may include a fractional component; for example, '.nr PSINCR 1.5p' sets a type size increment of 1.5p. This is a GNU extension. Effective: next heading. Default: 1p. -- Register: \n[GROWPS] Defines the heading depth above which the type size increment set by 'PSINCR' becomes effective. For each heading depth less than the value of 'GROWPS', the type size is increased by 'PSINCR'. Setting 'GROWPS' to any value less than 2 disables the incremental heading size feature. This is a GNU extension. Effective: next heading. Default: 0. -- Register: \n[HORPHANS] Defines the minimum number of lines of an immediately succeeding paragraph that should be kept together with any heading introduced by the 'NH' or 'SH' macros. If a heading is placed close to the bottom of a page, and there is insufficient space to accommodate both the heading and at least 'HORPHANS' lines of the following paragraph, before an automatic page break, then the page break is forced before the heading. This is a GNU extension. Effective: next paragraph. Default: 1. -- String: \*[SN-STYLE] Defines the style used to print numbered headings. *Note Headings in ms::. This is a GNU extension. Effective: next heading. Default: alias of 'SN-DOT' Footnote settings ................. -- Register: \n[FI] Defines the footnote indentation. This is a Berkeley extension. Effective: next footnote. Default: 2n. -- Register: \n[FF] Defines the format of automatically numbered footnotes, and those for which the 'FS' request is given a marker argument, at the bottom of a column or page. This is a Berkeley extension. '0' Set an automatic number(1) (*note ms Document Control Settings-Footnote-1::) as a superscript (on typesetter devices) or surrounded by square brackets (on terminals). The footnote paragraph is indented as with 'PP' if there is an 'FS' argument or an automatic number, and as with 'LP' otherwise. This is the default. '1' As '0', but set the marker as regular text and follow an automatic number with a period. '2' As '1', but without indentation (like 'LP'). '3' As '1', but set the footnote paragraph with the marker hanging (like 'IP'). Effective: next footnote. Default: 0. -- Register: \n[FPS] Defines the footnote type size. Effective: next footnote. Default: '\n[PS] - 2p'. -- Register: \n[FVS] Defines the footnote vertical spacing. Effective: next footnote. Default: '\n[FPS] + 2p'. -- Register: \n[FPD] Defines the footnote paragraph spacing. This is a GNU extension. Effective: next footnote. Default: '\n[PD] / 2'. -- String: \*[FR] Defines the ratio of the footnote line length to the current line length. This is a GNU extension. Effective: next footnote in single-column arrangements, next page otherwise. Default: '11/12'. Display settings ................ -- Register: \n[DD] Sets the display distance--the vertical spacing before and after a display, a 'tbl' table, an 'eqn' equation, or a 'pic' image. This is a Berkeley extension. Effective: next display boundary. Default: 0.5v (1v on low-resolution devices). -- Register: \n[DI] Sets the default amount by which to indent a display started with 'DS' and 'ID' without arguments, to '.DS I' without an indentation argument, and to equations set with '.EQ I'. This is a GNU extension. Effective: next indented display. Default: 0.5i. Other settings .............. -- Register: \n[MINGW] Defines the default minimum width between columns in a multi-column document. This is a GNU extension. Effective: next page. Default: 2n. -- Register: \n[TC-MARGIN] Defines the width of the field in which page numbers are set in a table of contents entry; the right margin thus moves inboard by this amount. This is a GNU extension. Effective: next 'PX' call. Default: '\w'000''  File: groff.info, Node: ms Document Control Settings-Footnotes, Up: ms Document Control Settings (1) defined in *note ms Footnotes::  File: groff.info, Node: ms Document Description Macros, Next: ms Body Text, Prev: ms Document Control Settings, Up: ms 4.6.4 Document Description Macros --------------------------------- Only the simplest document lacks a title.(1) (*note ms Document Description Macros-Footnote-1::) As its level of sophistication (or complexity) increases, it tends to acquire a date of revision, explicitly identified authors, sponsoring institutions for authors, and, at the rarefied heights, an abstract of its content. Define these data by calling the macros below in the order shown; 'DA' or 'ND' can be called to set the document date (or other identifier) at any time before (a) the abstract, if present, or (b) its information is required in a header or footer. Use of these macros is optional, except that 'TL' is mandatory if any of 'RP', 'AU', 'AI', or 'AB' is called, and 'AE' is mandatory if 'AB' is called. -- Macro: .RP [no-repeat-info] [no-renumber] Use the "report" (AT&T: "released paper") format for your document, creating a separate cover page. The default arrangement is to place most of the document description (title, author names and institutions, and abstract, but not the date) at the top of the first page. If the optional 'no-repeat-info' argument is given, 'ms' produces a cover page but does not repeat any of its information subsequently (but see the 'DA' macro below regarding the date). Normally, 'RP' sets the page number following the cover page to 1. Specifying the optional 'no-renumber' argument suppresses this alteration. Optional arguments can occur in any order. 'no' is recognized as a synonym of 'no-repeat-info' for 'AT&T' compatibility. -- Macro: .TL Specify the document title. 'ms' collects text on input lines following this call into the title until reaching 'AU', 'AB', or a heading or paragraphing macro call. -- Macro: .AU Specify an author's name. 'ms' collects text on input lines following this call into the author's name until reaching 'AI', 'AB', another 'AU', or a heading or paragraphing macro call. Call it repeatedly to specify multiple authors. -- Macro: .AI Specify the preceding author's institution. An 'AU' call is usefully followed by at most one 'AI' call; if there are more, the last 'AI' call controls. 'ms' collects text on input lines following this call into the author's institution until reaching 'AU', 'AB', or a heading or paragraphing macro call. -- Macro: .DA [x ...] Typeset the current date, or any arguments X, in the center footer, and, if 'RP' is also called, left-aligned at the end of the description information on the cover page. -- Macro: .ND [x ...] Typeset the current date, or any arguments X, if 'RP' is also called, left-aligned at the end of the document description on the cover page. This is 'groff' 'ms''s default. -- Macro: .AB [no] Begin the abstract. 'ms' collects text on input lines following this call into the abstract until reaching an 'AE' call. By default, 'ms' places the word "ABSTRACT" centered and in italics above the text of the abstract. The optional argument 'no' suppresses this heading. -- Macro: .AE End the abstract. An example document description, using a cover page, follows. .RP .TL The Inevitability of Code Bloat in Commercial and Free Software .AU J.\& Random Luser .AI University of West Bumblefuzz .AB This report examines the long-term growth of the code bases in two large, popular software packages; the free Emacs and the commercial Microsoft Word. While differences appear in the type or order of features added, due to the different methodologies used, the results are the same in the end. .PP The free software approach is shown to be superior in that while free software can become as bloated as commercial offerings, free software tends to have fewer serious bugs and the added features are more in line with user demand. .AE ...the rest of the paper...  File: groff.info, Node: ms Document Description Macros-Footnotes, Up: ms Document Description Macros (1) Distinguish a document title from "titles", which are what 'roff' systems call headers and footers collectively.  File: groff.info, Node: ms Body Text, Next: ms Page Layout, Prev: ms Document Description Macros, Up: ms 4.6.5 Body Text --------------- A variety of macros, registers, and strings can be used to structure and style the body of your document. They organize your text into paragraphs, headings, footnotes, and inclusions of material such as tables and figures. * Menu: * Text settings in ms:: * Typographical symbols in ms:: * Paragraphs in ms:: * Headings in ms:: * Typeface and decoration:: * Lists in ms:: * Indented regions in ms:: * ms keeps and displays:: * ms Insertions:: * ms Footnotes:: * ms language and localization::  File: groff.info, Node: Text settings in ms, Next: Typographical symbols in ms, Prev: ms Body Text, Up: ms Body Text 4.6.5.1 Text settings ..................... The 'FAM' string, a GNU extension, sets the font family for body text; the default is 'T'. The 'PS' and 'VS' registers set the type size and vertical spacing (distance between text baselines), respectively. The font family and type size are ignored on terminal devices. Setting these parameters before the first call of a heading, paragraphing, or (non-date) document description macro also applies them to headers, footers, and (for 'FAM') footnotes. Which font families are available depends on the output device; as a convention, 'T' selects a serif family ("Times"), 'H' a sans-serif family ("Helvetica"), and 'C' a monospaced family ("Courier"). The man page for the output driver documents its font repertoire. Consult the 'groff(1)' man page for lists of available output devices and their drivers. The hyphenation mode (as used by the 'hy' request) is set from the 'HY' register. Setting 'HY' to '0' is equivalent to using the 'nh' request. This is a Tenth Edition Research Unix extension.  File: groff.info, Node: Typographical symbols in ms, Next: Paragraphs in ms, Prev: Text settings in ms, Up: ms Body Text 4.6.5.2 Typographical symbols ............................. 'ms' provides a few strings to obtain typographical symbols not easily entered with the keyboard. These and many others are available as special character escape sequences--see the 'groff_char(7)' man page. -- String: \*[-] Interpolate an em dash. -- String: \*[Q] -- String: \*[U] Interpolate typographer's quotation marks where available, and neutral double quotes otherwise. '\*Q' is the left quote and '\*U' the right.  File: groff.info, Node: Paragraphs in ms, Next: Headings in ms, Prev: Typographical symbols in ms, Up: ms Body Text 4.6.5.3 Paragraphs .................. Paragraphing macros "break", or terminate, any pending output line so that a new paragraph can begin. Several paragraph types are available, differing in how indentation applies to them: to left, right, or both margins; to the first output line of the paragraph, all output lines, or all but the first. All paragraphing macro calls cause the insertion of vertical space in the amount stored in the 'PD' register, except at page or column breaks. Alternatively, a blank input line breaks the output line and vertically spaces by one vee. -- Macro: .LP Set a paragraph without any (additional) indentation. -- Macro: .PP Set a paragraph with a first-line left indentation in the amount stored in the 'PI' register. -- Macro: .IP [marker [width]] Set a paragraph with a left indentation. The optional MARKER is not indented and is empty by default. It has several applications; see *note Lists in ms::. WIDTH overrides the indentation amount stored in the 'PI' register; its default unit is 'n'. Once specified, WIDTH applies to further 'IP' calls until specified again or a heading or different paragraphing macro is called. -- Macro: .QP Set a paragraph indented from both left and right margins by the amount stored in the 'QI' register. -- Macro: .QS -- Macro: .QE Begin ('QS') and end ('QE') a region where each paragraph is indented from both margins by the amount stored in the 'QI' register. The text between 'QS' and 'QE' can be structured further by use of other paragraphing macros. -- Macro: .XP Set an "exdented" paragraph--one with a left indentation in the amount stored in the 'PI' register on every line _except_ the first (also known as a hanging indent). This is a Berkeley extension. The following example illustrates the use of paragraphing macros. .NH 2 Cases used in the 2001 study .LP Two software releases were considered for this report. .PP The first is commercial software; the second is free. .IP \[bu] Microsoft Word for Windows, starting with version 1.0 through the current version (Word 2000). .IP \[bu] GNU Emacs, from its first appearance as a standalone editor through the current version (v20). See [Bloggs 2002] for details. .QP Franklin's Law applied to software: software expands to outgrow both RAM and disk space over time. .SH Bibliography .XP Bloggs, Joseph R., .I "Everyone's a Critic" , Underground Press, March 2002. A definitive work that answers all questions and criticisms about the quality and usability of free software.  File: groff.info, Node: Headings in ms, Next: Typeface and decoration, Prev: Paragraphs in ms, Up: ms Body Text 4.6.5.4 Headings ................ Use headings to create a sequential or hierarchical structure for your document. The 'ms' macros print headings in *bold* using the same font family and, by default, type size as the body text. Headings are available with and without automatic numbering. Text on input lines following the macro call becomes the heading's title. Call a paragraphing macro to end the heading text and start the section's content. -- Macro: .NH [depth] -- Macro: .NH S heading-depth-index ... Set an automatically numbered heading. 'ms' produces a numbered heading the form A.B.C..., to any depth desired, with the numbering of each depth increasing automatically and being reset to zero when a more significant level is increased. "1" is the most significant or coarsest division of the document. Only non-zero values are output. If DEPTH is omitted, it is taken to be '1'. If you specify DEPTH such that an ascending gap occurs relative to the previous 'NH' call--that is, you "skip a depth", as by '.NH 1' and then '.NH 3'--'groff' 'ms' emits a warning on the standard error stream. Alternatively, you can give 'NH' a first argument of 'S', followed by integers to number the heading depths explicitly. Further automatic numbering, if used, resumes using the specified indices as their predecessors. This feature is a Berkeley extension. An example may be illustrative. .NH 1 Animalia .NH 2 Arthropoda .NH 3 Crustacea .NH 2 Chordata .NH S 6 6 6 Daimonia .NH 1 Plantae The above results in numbering as follows; the vertical space that normally precedes each heading is omitted. 1. Animalia 1.1. Arthropoda 1.1.1. Crustacea 1.2. Chordata 6.6.6. Daimonia 7. Plantae -- String: \*[SN-STYLE] -- String: \*[SN-DOT] -- String: \*[SN-NO-DOT] -- String: \*[SN] After 'NH' is called, the assigned number is made available in the strings 'SN-DOT' (as it appears in a printed heading with default formatting, followed by a terminating period) and 'SN-NO-DOT' (with the terminating period omitted). These are GNU extensions. You can control the style used to print numbered headings by defining an appropriate alias for the string 'SN-STYLE'. By default, 'SN-STYLE' is aliased to 'SN-DOT'. If you prefer to omit the terminating period from numbers appearing in numbered headings, you may define the alias as follows. .als SN-STYLE SN-NO-DOT Any such change in numbering style becomes effective from the next use of 'NH' following redefinition of the alias for 'SN-STYLE'. The formatted number of the current heading is available in the 'SN' string (a feature first documented by Berkeley), which facilitates its inclusion in, for example, table captions, equation labels, and 'XS'/'XA'/'XE' table of contents entries. -- Macro: .SH [depth] Set an unnumbered heading. The optional DEPTH argument is a GNU extension indicating the heading depth corresponding to the DEPTH argument of 'NH'. It matches the type size at which the heading is set to that of a numbered heading at the same depth when the 'GROWPS' and 'PSINCR' heading size adjustment mechanism is in effect. If the 'GROWPS' register is set to a value greater than the LEVEL argument to 'NH' or 'SH', the type size of a heading produced by these macros increases by 'PSINCR' units over the size specified by 'PS' multiplied by the difference of 'GROWPS' and LEVEL. The value stored in 'PSINCR' is interpreted in 'groff' basic units; the 'p' scaling unit should be employed when assigning a value specified in points. For example, the sequence .nr PS 10 .nr GROWPS 3 .nr PSINCR 1.5p .NH 1 Carnivora .NH 2 Felinae .NH 3 Felis catus .SH 2 Machairodontinae will cause "1. Carnivora" to be printed in 13-point text, followed by "1.1. Felinae" in 11.5-point text, while "1.1.1. Felis catus" and all more deeply nested heading levels will remain in the 10-point text specified by the 'PS' register. "Machairodontinae" is printed at 11.5 points, since it corresponds to heading level 2. The 'HORPHANS' register operates in conjunction with the 'NH' and 'SH' macros to inhibit the printing of isolated headings at the bottom of a page; it specifies the minimum number of lines of an immediately subsequent paragraph that must be kept on the same page as the heading. If insufficient space remains on the current page to accommodate the heading and this number of lines of paragraph text, a page break is forced before the heading is printed. Any display macro call or 'tbl', 'pic', or 'eqn' region between the heading and the subsequent paragraph suppresses this grouping. *Note ms keeps and displays:: and *note ms Insertions::.  File: groff.info, Node: Typeface and decoration, Next: Lists in ms, Prev: Headings in ms, Up: ms Body Text 4.6.5.5 Typeface and decoration ............................... The 'ms' macros provide a variety of ways to style text. Attend closely to the ordering of arguments labeled PRE and POST, which is not intuitive. Support for PRE arguments is a GNU extension.(1) (*note Typeface and decoration-Footnote-1::) -- Macro: .B [text [post [pre]]] Style TEXT in bold, followed by POST in the previous font style without intervening space, and preceded by PRE similarly. Without arguments, 'ms' styles subsequent text in bold until the next paragraphing, heading, or no-argument typeface macro call. -- Macro: .R [text [post [pre]]] As 'B', but use the roman style (upright text of normal weight) instead of bold. Argument recognition is a GNU extension. -- Macro: .I [text [post [pre]]] As 'B', but use an italic or oblique style instead of bold. -- Macro: .BI [text [post [pre]]] As 'B', but use a bold italic or bold oblique style instead of upright bold. This is a Tenth Edition Research Unix extension. -- Macro: .CW [text [post [pre]]] As 'B', but use a constant-width (monospaced) roman typeface instead of bold. This is a Tenth Edition Research Unix extension. -- Macro: .BX [text] Typeset TEXT and draw a box around it. On terminal devices, reverse video is used instead. If you want TEXT to contain space, use unbreakable space or horizontal motion escape sequences ('\~', '\', '\^', '\|', '\0' or '\h'). -- Macro: .UL [text [post]] Typeset TEXT with an underline. POST, if present, is set after TEXT with no intervening space. -- Macro: .LG Set subsequent text in larger type (two points larger than the current size) until the next type size, paragraphing, or heading macro call. You can specify this macro multiple times to enlarge the type size as needed. -- Macro: .SM Set subsequent text in smaller type (two points smaller than the current size) until the next type size, paragraphing, or heading macro call. You can specify this macro multiple times to reduce the type size as needed. -- Macro: .NL Set subsequent text at the normal type size (the amount in the 'PS' register). PRE and POST arguments are typically used to simplify the attachment of punctuation to styled words. When PRE is used, a hyphenation control escape sequence '\%' that would ordinarily start TEXT must start PRE instead to have the desired effect. The CS course's students found one C language keyword .CW static ) \%( most troublesome. The foregoing example produces output as follows. The CS course's students found one C language keyword (static) most troublesome. You can use the output line continuation escape sequence '\c' to achieve the same result (*note Line Continuation::). It is also portable to older 'ms' implementations. The CS course's students found one C language keyword \%(\c .CW \%static ) most troublesome. 'groff' 'ms' also offers strings to begin and end super- and subscripting. These are GNU extensions. -- String: \*[{] -- String: \*[}] Begin and end superscripting, respectively. -- String: \*[<] -- String: \*[>] Begin and end subscripting, respectively. Rather than calling the 'CW' macro, in 'groff' 'ms' you might prefer to change the font family to Courier by setting the 'FAM' string to 'C'. You can then use all four style macros above, returning to the default family (Times) with '.ds FAM T'. Because changes to 'FAM' take effect only at the next paragraph, 'CW' remains useful to "inline" a change to the font family, similarly to the practice of this document in noting syntactical elements of 'ms' and 'groff'.  File: groff.info, Node: Typeface and decoration-Footnotes, Up: Typeface and decoration (1) This idiosyncrasy arose through feature accretion; for example, the 'B' macro in Version 6 Unix 'ms' (1975) accepted only one argument, the text to be set in boldface. By Version 7 (1979) it recognized a second argument; in 1990, 'groff' 'ms' added a "pre" argument, placing it third to avoid breaking support for older documents.  File: groff.info, Node: Lists in ms, Next: Indented regions in ms, Prev: Typeface and decoration, Up: ms Body Text 4.6.5.6 Lists ............. The MARKER argument to the 'IP' macro can be employed to present a variety of lists; for instance, you can use a bullet glyph ('\[bu]') for unordered lists, a number (or auto-incrementing register) for numbered lists, or a word or phrase for glossary-style or definition lists. If you set the paragraph indentation register 'PI' before calling 'IP', you can later reorder the items in the list without having to ensure that a WIDTH argument remains affixed to the first call. The following is an example of a bulleted list. .nr PI 2n A bulleted list: .IP \[bu] lawyers .IP \[bu] guns .IP \[bu] money A bulleted list: * lawyers * guns * money The following is an example of a numbered list. .nr step 0 1 .nr PI 3n A numbered list: .IP \n+[step] lawyers .IP \n+[step] guns .IP \n+[step] money A numbered list: 1. lawyers 2. guns 3. money Here we have employed the 'nr' request to create a register of our own, 'step'. We initialized it to zero and assigned it an auto-increment of 1. Each time we use the escape sequence '\n+[PI]' (note the plus sign), the formatter applies the increment just before interpolating the register's value. Preparing the 'PI' register as well enables us to rearrange the list without the tedium of updating macro calls. The next example illustrates a glossary-style list. A glossary-style list: .IP lawyers 0.4i Two or more attorneys. .IP guns Firearms, preferably large-caliber. .IP money Gotta pay for those lawyers and guns! A glossary-style list: lawyers Two or more attorneys. guns Firearms, preferably large-caliber. money Gotta pay for those lawyers and guns! In the previous example, observe how the 'IP' macro places the definition on the same line as the term if it has enough space. If this is not what you want, there are a few workarounds we will illustrate by modifying the example. First, you can use a 'br' request to force a break after printing the term or label. .IP guns .br Firearms, Second, you could apply the '\p' escape sequence to force a break. The space following the escape sequence is important; if you omit it, 'groff' prints the first word of the paragraph text on the same line as the term or label (if it fits) _then_ breaks the line. .IP guns \p Firearms, Finally, you may append a horizontal motion to the marker with the '\h' escape sequence; using the same amount as the indentation will ensure that the marker is too wide for 'groff' to treat it as "fitting" on the same line as the paragraph text. .IP guns\h'0.4i' Firearms, In each case, the result is the same. A glossary-style list: lawyers Two or more attorneys. guns Firearms, preferably large-caliber. money Gotta pay for those lawyers and guns!  File: groff.info, Node: Indented regions in ms, Next: ms keeps and displays, Prev: Lists in ms, Up: ms Body Text 4.6.5.7 Indented regions ........................ You may need to indent a region of text while otherwise formatting it normally. Indented regions can be nested; you can change '\n[PI]' before each call to vary the amount of inset. -- Macro: .RS Begin a region where headings, paragraphs, and displays are indented (further) by the amount stored in the 'PI' register. -- Macro: .RE End the (next) most recent indented region. This feature enables you to easily line up text under hanging and indented paragraphs. For example, you may wish to structure lists hierarchically. .IP \[bu] 2 Lawyers: .RS .IP \[bu] Dewey, .IP \[bu] Cheatham, and .IP \[bu] and Howe. .RE .IP \[bu] Guns * Lawyers: * Dewey, * Cheatham, and * Howe. * Guns  File: groff.info, Node: ms keeps and displays, Next: ms Insertions, Prev: Indented regions in ms, Up: ms Body Text 4.6.5.8 Keeps, boxed keeps, and displays ........................................ On occasion, you may want to "keep" several lines of text, or a region of a document, together on a single page, preventing an automatic page break within certain boundaries. This can cause a page break to occur earlier than it normally would. For example, you may want to keep two paragraphs together, or a paragraph that refers to a table, list, or figure adjacent to the item it discusses. 'ms' provides the 'KS' and 'KE' macros for this purpose. You can alternatively specify a "floating keep": if a keep cannot fit on the current page, 'ms' holds its contents and allows material following the keep (in the source document) to fill the remainder of the current page. When the page breaks, whether by reaching the end or 'bp' request, 'ms' puts the floating keep at the beginning of the next page. This is useful for placing large graphics or tables that do not need to appear exactly where they occur in the source document. -- Macro: .KS -- Macro: .KF -- Macro: .KE 'KS' begins a keep, 'KF' a floating keep, and 'KE' ends a keep of either kind. As an alternative to the keep mechanism, the 'ne' request forces a page break if there is not at least the amount of vertical space specified in its argument remaining on the page (*note Page Control::). One application of 'ne' is to reserve space on the page for a figure or illustration to be included later. A "boxed keep" has a frame drawn around it. -- Macro: .B1 -- Macro: .B2 'B1' begins a keep with a box drawn around it. 'B2' ends a boxed keep. Boxed keep macros cause breaks; if you need to box a word or phrase within a line, see the 'BX' macro in *note Typeface and decoration::. Box lines are drawn as close as possible to the text they enclose so that they are usable within paragraphs. If you wish to box one or more paragraphs, you may improve the appearance by calling 'B1' after the first paragraphing macro, and by adding a small amount of vertical space before calling 'B2'. .LP .B1 .I Warning: Happy Fun Ball may suddenly accelerate to dangerous speeds. .sp \n[PD]/2 \" space by half the inter-paragraph distance .B2 If you want a boxed keep to float, you will need to enclose the 'B1' and 'B2' calls within a pair of 'KF' and 'KE' calls. "Displays" turn off filling; lines of verse or program code are shown with their lines broken as in the source document without requiring 'br' requests between lines. Displays can be kept on a single page or allowed to break across pages. The 'DS' macro begins a kept display of the layout specified in its first argument; non-kept displays are begun with dedicated macros corresponding to their layout. -- Macro: .DS L -- Macro: .LD Begin ('DS': kept) left-aligned display. -- Macro: .DS [I [indent]] -- Macro: .ID [indent] Begin ('DS': kept) display indented by INDENT if specified, and by the amount of the 'DI' register otherwise. -- Macro: .DS B -- Macro: .BD Begin a ('DS': kept) a block display: the entire display is left-aligned, but indented such that the longest line in the display is centered on the page. -- Macro: .DS C -- Macro: .CD Begin a ('DS': kept) centered display: each line in the display is centered. -- Macro: .DS R -- Macro: .RD Begin a ('DS': kept) right-aligned display. This is a GNU extension. -- Macro: .DE End any display. The distance stored in the 'DD' register is inserted before and after each pair of display macros; this is a Berkeley extension. In 'groff' 'ms', this distance replaces any adjacent inter-paragraph distance or subsequent spacing prior to a section heading. The 'DI' register is a GNU extension; its value is an indentation applied to displays created with '.DS' and '.ID' without arguments, to '.DS I' without an indentation argument, and to indented equations set with '.EQ'. Changes to either register take effect at the next display boundary.  File: groff.info, Node: ms Insertions, Next: ms Footnotes, Prev: ms keeps and displays, Up: ms Body Text 4.6.5.9 Tables, figures, equations, and references .................................................. The 'ms' package is often used with the 'tbl', 'pic', 'eqn', and 'refer' preprocessors. Mark text meant for preprocessors by enclosing it in pairs of tokens as follows, with nothing between the dot and the macro name. The preprocessors match these tokens only at the start of an input line. -- Macro: .TS [H] -- Macro: .TE Demarcate a table to be processed by the 'tbl' preprocessor. The optional argument 'H' to 'TS' instructs 'ms' to repeat table rows (often column headings) at the top of each new page the table spans, if applicable; calling the 'TH' macro marks the end of such rows. The GNU 'tbl(1)' man page provides a comprehensive reference to the preprocessor and offers examples of its use. -- Macro: .PS -- Macro: .PE -- Macro: .PF 'PS' begins a picture to be processed by the 'gpic' preprocessor; either of 'PE' or 'PF' ends it, the latter with "flyback" to the vertical position at its top. You can create 'pic' input manually or with a program such as 'xfig'. -- Macro: .EQ [align [label]] -- Macro: .EN Demarcate an equation to be processed by the 'eqn' preprocessor. The equation is centered by default; ALIGN can be 'C', 'L', or 'I' to (explicitly) center, left-align, or indent it by the amount stored in the 'DI' register, respectively. If specified, LABEL is set right-aligned. -- Macro: .[ -- Macro: .] Demarcate a bibliographic citation to be processed by the 'refer' preprocessor. The GNU 'refer(1)' man page provides a comprehensive reference to the preprocessor and the format of its bibliographic database. Type 'man refer' at the command line to view it. When 'refer' emits collected references (as might be done on a "Works Cited" page), it interpolates the 'REFERENCES' string as an unnumbered heading ('SH'). The following is an example of how to set up a table that may print across two or more pages. .TS H allbox; Cb | Cb . Part->Description _ .TH .T& GH-1978->Fribulating gonkulator ...the rest of the table follows... .TE Attempting to place a multi-page table inside a keep can lead to unpleasant results, particularly if the 'tbl' 'allbox' option is used. Mathematics can be typeset using the language of the 'eqn' preprocessor. .EQ C (\*[SN-NO-DOT]a) p ~ = ~ q sqrt { ( 1 + ~ ( x / q sup 2 ) } .EN This input formats a labelled equation. We used the 'SN-NO-DOT' string to base the equation label on the current heading number, giving us more flexibility to reorganize the document. Use 'groff' options to run preprocessors on the input: '-e' for 'geqn', '-p' for 'gpic', '-R' for 'grefer', and '-t' for 'gtbl'.  File: groff.info, Node: ms Footnotes, Prev: ms Insertions, Up: ms Body Text 4.6.5.10 Footnotes .................. A footnote is typically anchored to a place in the text with a "marker", which is a small integer, a symbol such as a dagger, or arbitrary user-specified text. -- String: \*[*] Place an "automatic number", an automatically generated numeric footnote marker, in the text. Each time this string is interpolated, the number it produces increments by one. Automatic numbers start at 1. This is a Berkeley extension. Enclose the footnote text in 'FS' and 'FE' macro calls to set it at the nearest available "foot", or bottom, of a text column or page. -- Macro: .FS [marker] -- Macro: .FE Begin ('FS') and end ('FE') a footnote. 'FS' calls 'FS-MARK' with any supplied MARKER argument, which is then also placed at the beginning of the footnote text. If MARKER is omitted, the next pending automatic footnote number enqueued by interpolation of the '*' string is used, and if none exists, nothing is prefixed. You may not desire automatically numbered footnotes in spite of their convenience. You can indicate a footnote with a symbol or other text by specifying its marker at the appropriate place (for example, by using '\[dg]' for the dagger glyph) _and_ as an argument to the 'FS' macro. Such manual marks should be repeated as arguments to 'FS' or as part of the footnote text to disambiguate their correspondence. You may wish to use '\*{' and '\*}' to superscript the marker at the anchor point, in the footnote text, or both. 'groff' 'ms' provides a hook macro, 'FS-MARK', for user-determined operations to be performed when the 'FS' macro is called. It is passed the same arguments as 'FS' itself. An application of 'FS-MARK' is anchor placement for a hyperlink reference, so that a footnote can link back to its referential context.(1) (*note ms Footnotes-Footnote-1::) By default, this macro has an empty definition. 'FS-MARK' is a GNU extension. Footnotes can be safely used within keeps and displays, but you should avoid using automatically numbered footnotes within floating keeps. You can place a second '\**' interpolation between a '\**' and its corresponding 'FS' call as long as each 'FS' call occurs _after_ the corresponding '\**' and occurrences of 'FS' are in the same order as corresponding occurrences of '\**'. Footnote text is formatted as paragraphs are, using analogous parameters. The registers 'FI', 'FPD', 'FPS', and 'FVS' correspond to 'PI', 'PD', 'PS', and 'CS', respectively; 'FPD', 'FPS', and 'FVS' are GNU extensions. The 'FF' register controls the formatting of automatically numbered footnote paragraphs and those for which 'FS' is given a marker argument. *Note ms Document Control Settings::. The default footnote line length is 11/12ths of the normal line length for compatibility with the expectations of historical 'ms' documents; you may wish to set the 'FR' string to '1' to align with contemporary typesetting practices. In the past,(2) (*note ms Footnotes-Footnote-2::) an 'FL' register was used for the line length in footnotes; however, setting this register at document initialization time had no effect on the footnote line length in multi-column arrangements.(3) (*note ms Footnotes-Footnote-3::) 'FR' should be used in preference to the old 'FL' register in contemporary documents. The footnote line length is effectively computed as 'column-width * \*[FR]'. If an absolute footnote line length is required, recall that arithmetic expressions in 'roff' input are evaluated strictly from left to right, with no operator precedence (parentheses are honored). .ds FR 0+3i \" Set footnote line length to 3 inches.  File: groff.info, Node: ms Footnotes-Footnotes, Up: ms Footnotes (1) "Portable Document Format Publishing with GNU Troff", 'pdfmark.ms' in the 'groff' distribution, uses this technique. (2) Unix Version 7 'ms', its descendants, and GNU 'ms' prior to 'groff' version 1.23.0 (3) You could reset it after each call to '.1C', '.2C', or '.MC'.  File: groff.info, Node: ms language and localization, Next: ms Page Layout, Prev: ms Footnotes, Up: ms Body Text 4.6.5.11 Language and localization .................................. 'groff' 'ms' provides several strings that you can customize for your own purposes, or redefine to adapt the macro package to languages other than English. It is already localized for Czech, German, French, Italian, and Swedish. Load the desired localization macro package after 'ms'; see the 'groff_tmac(5)' man page. $ groff -ms -mfr bienvenue.ms The following strings are available. -- String: \*[REFERENCES] Contains the string printed at the beginning of a references (bibliography) page produced with GNU 'refer(1)'. The default is 'References'. -- String: \*[ABSTRACT] Contains the string printed at the beginning of the abstract. The default is '\f[I]ABSTRACT\f[]'; it includes font selection escape sequences to set the word in italics. -- String: \*[TOC] Contains the string printed at the beginning of the table of contents. The default is 'Table of Contents'. -- String: \*[MONTH1] -- String: \*[MONTH2] -- String: \*[MONTH3] -- String: \*[MONTH4] -- String: \*[MONTH5] -- String: \*[MONTH6] -- String: \*[MONTH7] -- String: \*[MONTH8] -- String: \*[MONTH9] -- String: \*[MONTH10] -- String: \*[MONTH11] -- String: \*[MONTH12] Contain the full names of the calendar months. The defaults are in English: 'January', 'February', and so on.  File: groff.info, Node: ms Page Layout, Next: Differences from AT&T ms, Prev: ms Body Text, Up: ms 4.6.6 Page layout ----------------- 'ms''s default page layout arranges text in a single column with the page number between hyphens centered in a header on each page except the first, and produces no footers. You can customize this arrangement. * Menu: * ms Headers and Footers:: * Tab Stops in ms:: * ms Margins:: * ms Multiple Columns:: * ms TOC::  File: groff.info, Node: ms Headers and Footers, Next: Tab Stops in ms, Prev: ms Page Layout, Up: ms Page Layout 4.6.6.1 Headers and footers ........................... There are multiple ways to produce headers and footers. One is to define the strings 'LH', 'CH', and 'RH' to set the left, center, and right headers, respectively; and 'LF', 'CF', and 'RF' to set the left, center, and right footers. This approach suffices for documents that do not distinguish odd- and even-numbered pages. Another method is to call macros that set headers or footers for odd- or even-numbered pages. Each such macro takes a delimited argument separating the left, center, and right header or footer texts from each other. You can replace the neutral apostrophes (''') shown below with any character not appearing in the header or footer text. These macros are Berkeley extensions. -- Macro: .OH 'left'center'right' -- Macro: .EH 'left'center'right' -- Macro: .OF 'left'center'right' -- Macro: .EF 'left'center'right' The 'OH' and 'EH' macros define headers for odd- (recto) and even-numbered (verso) pages, respectively; the 'OF' and 'EF' macros define footers for them. With either method, a percent sign '%' in header or footer text is replaced by the current page number. By default, 'ms' places no header on a page numbered "1" (regardless of its number format). -- Macro: .P1 Typeset the header even on page 1. To be effective, this macro must be called before the header trap is sprung on any page numbered "1"; in practice, unless your page numbering is unusual, this means that you should call it early, before 'TL' or any heading or paragraphing macro. This is a Berkeley extension. For even greater flexibility, 'ms' is designed to permit the redefinition of the macros that are called when the 'groff' traps that ordinarily cause the headers and footers to be output are sprung. 'PT' ("page trap") is called by 'ms' when the header is to be written, and 'BT' ("bottom trap") when the footer is to be. The 'groff' page location trap that 'ms' sets up to format the header also calls the (normally undefined) 'HD' macro after 'PT'; you can define 'HD' if you need additional processing after setting the header (for example, to draw a line below it). The 'HD' hook is a Berkeley extension. Any such macros you (re)define must implement any desired specialization for odd-, even-, or first numbered pages.  File: groff.info, Node: Tab Stops in ms, Next: ms Margins, Prev: ms Headers and Footers, Up: ms Page Layout 4.6.6.2 Tab stops ................. Use the 'ta' request to define tab stops as needed. *Note Tabs and Fields::. -- Macro: .TA Reset the tab stops to the 'ms' default (every 5 ens). Redefine this macro to create a different set of default tab stops.  File: groff.info, Node: ms Margins, Next: ms Multiple Columns, Prev: Tab Stops in ms, Up: ms Page Layout 4.6.6.3 Margins ............... Control margins using the registers summarized in "Margin settings" in *note ms Document Control Settings:: above. There is no setting for the right margin; the combination of page offset '\n[PO]' and line length '\n[LL]' determines it.  File: groff.info, Node: ms Multiple Columns, Next: ms TOC, Prev: ms Margins, Up: ms Page Layout 4.6.6.4 Multiple columns ........................ 'ms' can set text in as many columns as reasonably fit on the page. The following macros force a page break if a multi-column layout is active when they are called. The 'MINGW' register stores the default minimum gutter width; it is a GNU extension. When multiple columns are in use, keeps and the 'HORPHANS' and 'PORPHANS' registers work with respect to column breaks instead of page breaks. -- Macro: .1C Arrange page text in a single column (the default). -- Macro: .2C Arrange page text in two columns. -- Macro: .MC [column-width [gutter-width]] Arrange page text in multiple columns. If you specify no arguments, it is equivalent to the '2C' macro. Otherwise, COLUMN-WIDTH is the width of each column and GUTTER-WIDTH is the minimum distance between columns.  File: groff.info, Node: ms TOC, Next: Differences from AT&T ms, Prev: ms Multiple Columns, Up: ms Page Layout 4.6.6.5 Creating a table of contents .................................... Because 'roff' formatters process their input in a single pass, material on page 50, for example, cannot influence what appears on page 1--this poses a challenge for a table of contents at its traditional location in front matter, if you wish to avoid manually maintaining it. 'ms' enables the collection of material to be presented in the table of contents as it appears, saving its page number along with it, and then emitting the collected contents on demand toward the end of the document. The table of contents can then be resequenced to its desired location by physically rearranging the pages of a printed document, or as part of post-processing--with a 'sed(1)' script to reorder the pages in 'troff''s output, with 'pdfjam(1)', or with 'gropdf(1)''s '.pdfswitchtopage' feature, for example. Define an entry to appear in the table of contents by bracketing its text between calls to the 'XS' and 'XE' macros. A typical application is to call them immediately after 'NH' or 'SH' and repeat the heading text within them. The 'XA' macro, used within '.XS'/'.XE' pairs, supplements an entry--for instance, when it requires multiple output lines, whether because a heading is too long to fit or because style dictates that page numbers not be repeated. You may wish to indent the text thus wrapped to correspond to its heading depth; this can be done in the entry text by prefixing it with tabs or horizontal motion escape sequences, or by providing a second argument to the 'XA' macro. 'XS' and 'XA' automatically associate the page number where they are called with the text following them, but they accept arguments to override this behavior. At the end of the document, call 'TC' or 'PX' to emit the table of contents; 'TC' resets the page number to 'i' (Roman numeral one), and then calls 'PX'. All of these macros are Berkeley extensions. -- Macro: .XS [page-number] -- Macro: .XA [page-number [indentation]] -- Macro: .XE Begin, supplement, and end a table of contents entry. Each entry is associated with PAGE-NUMBER (otherwise the current page number); a PAGE-NUMBER of 'no' prevents a leader and page number from being emitted for that entry. Use of 'XA' within 'XS'/'XE' is optional; it can be repeated. If INDENTATION is present, a supplemental entry is indented by that amount; ens are assumed if no unit is indicated. Text on input lines between 'XS' and 'XE' is stored for later recall by 'PX'. -- Macro: .PX [no] Switch to single-column layout. Unless 'no' is specified, center and interpolate the 'TOC' string in bold and two points larger than the body text. Emit the table of contents entries. -- Macro: .TC [no] Set the page number to 1, the page number format to lowercase Roman numerals, and call 'PX' (with a 'no' argument, if present). Here's an example of typical 'ms' table of contents preparation. We employ horizontal escape sequences '\h' to indent the entries by sectioning depth. .NH 1 Introduction .XS Introduction .XE ... .NH 2 Methodology .XS \h'2n'Methodology .XA \h'4n'Fassbinder's Approach \h'4n'Kahiu's Approach .XE ... .NH 1 Findings .XS Findings .XE ... .TC The remaining features in this subsubsection are GNU extensions. 'groff' 'ms' obviates the need to repeat heading text after 'XS' calls. Call 'XN' and 'XH' after 'NH' and 'SH', respectively. -- Macro: .XN heading-text -- Macro: .XH depth heading-text Format HEADING-TEXT and create a corresponding table of contents entry. 'XN' computes the indentation from the depth of the preceding 'NH' call; 'XH' requires a DEPTH argument to do so. 'groff' 'ms' encourages customization of table of contents entry production. -- Macro: .XN-REPLACEMENT heading-text -- Macro: .XH-REPLACEMENT depth heading-text These hook macros implement 'XN' and 'XH', respectively. They call 'XN-INIT' and pass their HEADING-TEXT arguments to 'XH-UPDATE-TOC'. -- Macro: .XN-INIT -- Macro: .XH-UPDATE-TOC depth heading-text The 'XN-INIT' hook macro does nothing by default. 'XH-UPDATE-TOC' brackets HEADING-TEXT with 'XS' and 'XE' calls, indenting it by 2 ens per level of DEPTH beyond the first. We could therefore produce a table of contents similar to that in the previous example with fewer macro calls. (The difference is that this input follows the "Approach" entries with leaders and page numbers.) .NH 1 .XN Introduction ... .NH 2 .XN Methodology .XH 3 "Fassbinder's Approach" .XH 3 "Kahiu's Approach" ... .NH 1 .XN Findings ... To get the section number of the numbered headings into the table of contents entries, we might define 'XN-REPLACEMENT' as follows. (We obtain the heading depth from 'groff' 'ms''s internal register 'nh*hl'.) .de XN-REPLACEMENT .XN-INIT .XH-UPDATE-TOC \\n[nh*hl] \\$@ \&\\*[SN] \\$* .. You can change the style of the leader that bridges each table of contents entry with its page number; define the 'TC-LEADER' special character by using the 'char' request. A typical leader combines the dot glyph '.' with a horizontal motion escape sequence to spread the dots. The width of the page number field is stored in the 'TC-MARGIN' register.  File: groff.info, Node: Differences from AT&T ms, Next: ms Naming Conventions, Prev: ms Page Layout, Up: ms 4.6.7 Differences from AT&T 'ms' -------------------------------- The 'groff' 'ms' macros are an independent reimplementation, using no AT&T code. Since they take advantage of the extended features of 'groff', they cannot be used with AT&T 'troff'. 'groff' 'ms' supports features described above as Berkeley and Tenth Edition Research Unix extensions, and adds several of its own. * The internals of 'groff' 'ms' differ from the internals of AT&T 'ms'. Documents that depend upon implementation details of AT&T 'ms' may not format properly with 'groff' 'ms'. Such details include macros whose function was not documented in the AT&T 'ms' manual.(1) (*note Differences from AT&T ms-Footnote-1::) * The error-handling policy of 'groff' 'ms' is to detect and report errors, rather than to ignore them silently. * Tenth Edition Research Unix supported 'P1'/'P2' macros to bracket code examples; 'groff' 'ms' does not. * 'groff' 'ms' does not work in GNU 'troff''s AT&T compatibility mode. If loaded when that mode is enabled, it aborts processing with a diagnostic message. * Multiple line spacing is not supported. Use a larger vertical spacing instead. * 'groff' 'ms' uses the same header and footer defaults in both 'nroff' and 'troff' modes as AT&T 'ms' does in 'troff' mode; AT&T's default in 'nroff' mode is to put the date, in U.S. traditional format (e.g., "January 1, 2021"), in the center footer (the 'CF' string). * Many 'groff' 'ms' macros, including those for paragraphs, headings, and displays, cause a reset of paragraph rendering parameters, and may change the indentation; they do so not by incrementing or decrementing it, but by setting it absolutely. This can cause problems for documents that define additional macros of their own that try to manipulate indentation. Use the 'ms' 'RS' and 'RE' macros instead of the 'in' request. * AT&T 'ms' interpreted the values of the registers 'PS' and 'VS' in points, and did not support the use of scaling units with them. 'groff' 'ms' interprets values of the registers 'PS', 'VS', 'FPS', and 'FVS' equal to or larger than 1,000 (one thousand) as decimal fractions multiplied by 1,000.(2) (*note Differences from AT&T ms-Footnote-2::) This threshold makes use of a scaling unit with these parameters practical for high-resolution devices while preserving backward compatibility. It also permits expression of non-integral type sizes. For example, 'groff -rPS=10.5p' at the shell prompt is equivalent to placing '.nr PS 10.5p' at the beginning of the document. * AT&T 'ms''s 'AU' macro supported arguments used with some document types; 'groff' 'ms' does not. * Right-aligned displays are available. The AT&T 'ms' manual observes that "it is tempting to assume that '.DS R' will right adjust lines, but it doesn't work". In 'groff' 'ms', it does. * To make 'groff' 'ms' use the default page offset (which also specifies the left margin), the 'PO' register must stay undefined until the first 'ms' macro is called. This implies that '\n[PO]' should not be used early in the document, unless it is changed also: accessing an undefined register automatically defines it. * 'groff' 'ms' supports the 'PN' register, but it is not necessary; you can access the page number via the usual '%' register and invoke the 'af' request to assign a different format to it if desired.(3) (*note Differences from AT&T ms-Footnote-3::) * The AT&T 'ms' manual documents registers 'CW' and 'GW' as setting the default column width and "intercolumn gap", respectively, and which applied when 'MC' was called with fewer than two arguments. 'groff' 'ms' instead treats 'MC' without arguments as synonymous with '2C'; there is thus no occasion for a default column width register. Further, the 'MINGW' register and the second argument to 'MC' specify a _minimum_ space between columns, not the fixed gutter width of AT&T 'ms'. * The AT&T 'ms' manual did not document the 'QI' register; Berkeley and 'groff' 'ms' do. -- Register: \n[GS] The register 'GS' is set to 1 by the 'groff' 'ms' macros, but is not used by the AT&T 'ms' package. Documents that need to determine whether they are being formatted with 'groff' 'ms' or another implementation should test this register. * Menu: * Missing Unix Version 7 ms Macros::  File: groff.info, Node: Differences from AT&T ms-Footnotes, Up: Differences from AT&T ms (1) 'Typing Documents on the UNIX System: Using the -ms Macros with Troff and Nroff', M. E. Lesk, Bell Laboratories, 1978 (2) Register values are converted to and stored as basic units. *Note Measurements::. (3) If you redefine the 'ms' 'PT' macro and desire special treatment of certain page numbers (like '1'), you may need to handle a non-Arabic page number format, as 'groff' 'ms''s 'PT' does; see the macro package source. 'groff' 'ms' aliases the 'PN' register to '%'.  File: groff.info, Node: Missing Unix Version 7 ms Macros, Prev: Differences from AT&T ms, Up: Differences from AT&T ms 4.6.7.1 Unix Version 7 'ms' macros not implemented by 'groff' 'ms' .................................................................. Several macros described in the Unix Version 7 'ms' documentation are unimplemented by 'groff' 'ms' because they are specific to the requirements of documents produced internally by Bell Laboratories, some of which also require a glyph for the Bell System logo that 'groff' does not support. These macros implemented several document type formats ('EG', 'IM', 'MF', 'MR', 'TM', 'TR'), were meaningful only in conjunction with the use of certain document types ('AT', 'CS', 'CT', 'OK', 'SG'), stored the postal addresses of Bell Labs sites ('HO', 'IH', 'MH', 'PY', 'WH'), or lacked a stable definition over time ('UX'). To compatibly render historical 'ms' documents using these macros, we advise your documents to invoke the 'rm' request to remove any such macros it uses and then define replacements with an authentically typeset original at hand.(1) (*note Missing Unix Version 7 ms Macros-Footnote-1::) For informal purposes, a simple definition of 'UX' should maintain the readability of the document's substance. .rm UX .ds UX Unix\"  File: groff.info, Node: Missing Unix Version 7 ms Macros-Footnotes, Up: Missing Unix Version 7 ms Macros (1) The removal beforehand is necessary because 'groff' 'ms' aliases these macros to a diagnostic macro, and you want to redefine the aliased name, not its target.  File: groff.info, Node: ms Legacy Features, Next: ms Naming Conventions, Prev: Differences from AT&T ms, Up: ms 4.6.8 Legacy Features --------------------- 'groff' 'ms' retains some legacy features solely to support formatting of historical documents; contemporary ones should not use them because they can render poorly. See the 'groff_char(7)' man page. AT&T accent mark strings ........................ AT&T 'ms' defined accent mark strings as follows. -- String: \*['] Apply acute accent to subsequent glyph. -- String: \*[`] Apply grave accent to subsequent glyph. -- String: \*[:] Apply dieresis (umlaut) to subsequent glyph. -- String: \*[^] Apply circumflex accent to subsequent glyph. -- String: \*[~] Apply tilde accent to subsequent glyph. -- String: \*[C] Apply caron to subsequent glyph. -- String: \*[,] Apply cedilla to subsequent glyph. Berkeley accent mark and glyph strings ...................................... Berkeley 'ms' offered an 'AM' macro; calling it redefined the AT&T accent mark strings (except for '\*C'), applied them to the _preceding_ glyph, and defined additional strings, some for spacing glyphs. -- Macro: .AM Enable alternative accent mark and glyph-producing strings. -- String: \*['] Apply acute accent to preceding glyph. -- String: \*[`] Apply grave accent to preceding glyph. -- String: \*[:] Apply dieresis (umlaut) to preceding glyph. -- String: \*[^] Apply circumflex accent to preceding glyph. -- String: \*[~] Apply tilde accent to preceding glyph. -- String: \*[,] Apply cedilla to preceding glyph. -- String: \*[/] Apply stroke (slash) to preceding glyph. -- String: \*[v] Apply caron to preceding glyph. -- String: \*[_] Apply macron to preceding glyph. -- String: \*[.] Apply underdot to preceding glyph. -- String: \*[o] Apply ring accent to preceding glyph. -- String: \*[?] Interpolate inverted question mark. -- String: \*[!] Interpolate inverted exclamation mark. -- String: \*[8] Interpolate small letter sharp s. -- String: \*[q] Interpolate small letter o with hook accent (ogonek). -- String: \*[3] Interpolate small letter yogh. -- String: \*[d-] Interpolate small letter eth. -- String: \*[D-] Interpolate capital letter eth. -- String: \*[th] Interpolate small letter thorn. -- String: \*[Th] Interpolate capital letter thorn. -- String: \*[ae] Interpolate small æ ligature. -- String: \*[Ae] Interpolate capital Æ ligature. -- String: \*[oe] Interpolate small oe ligature. -- String: \*[OE] Interpolate capital OE ligature.  File: groff.info, Node: ms Naming Conventions, Prev: ms Legacy Features, Up: ms 4.6.9 Naming Conventions ------------------------ The following conventions are used for names of macros, strings, and registers. External names available to documents that use the 'groff' 'ms' macros contain only uppercase letters and digits. Internally, the macros are divided into modules. Conventions for identifier names are as follows. * Names used only within one module are of the form MODULE'*'NAME. * Names used outside the module in which they are defined are of the form MODULE'@'NAME. * Names associated with a particular environment are of the form ENVIRONMENT':'NAME; these are used only within the 'par' module. * NAME does not have a module prefix. * Constructed names used to implement arrays are of the form ARRAY'!'INDEX. Thus the 'groff' 'ms' macros reserve the following names. * Names containing the characters '*', '@', and ':'. * Names containing only uppercase letters and digits.  File: groff.info, Node: GNU troff Reference, Next: File Formats, Prev: Major Macro Packages, Up: Top 5 GNU 'troff' Reference *********************** This chapter covers _all_ of the facilities of the GNU 'troff' formatting engine. Users of macro packages may skip it if not interested in details. * Menu: * Text:: * Page Geometry:: * Measurements:: * Numeric Expressions:: * Identifiers:: * Formatter Instructions:: * Comments:: * Registers:: * Manipulating Filling and Adjustment:: * Manipulating Hyphenation:: * Manipulating Spacing:: * Tabs and Fields:: * Character Translations:: * troff and nroff Modes:: * Line Layout:: * Line Continuation:: * Page Layout:: * Page Control:: * Using Fonts:: * Manipulating Type Size and Vertical Spacing:: * Colors:: * Strings:: * Conditionals and Loops:: * Writing Macros:: * Page Motions:: * Drawing Geometric Objects:: * Deferring Output:: * Traps:: * Diversions:: * Punning Names:: * Environments:: * Suppressing Output:: * I/O:: * Postprocessor Access:: * Miscellaneous:: * Gtroff Internals:: * Debugging:: * Implementation Differences::  File: groff.info, Node: Text, Next: Measurements, Prev: GNU troff Reference, Up: GNU troff Reference 5.1 Text ======== AT&T 'troff' was designed to take input as it would be composed on a typewriter, including the teletypewriters used as early computer terminals, and relieve the user drafting a document of concern with details like line length, hyphenation breaking, and the achievement of straight margins. Early in its development, the program gained the ability to prepare output for a phototypesetter; a document could then be prepared for output to either a teletypewriter, a phototypesetter, or both. GNU 'troff' continues this tradition of permitting an author to compose a single master version of a document which can then be rendered for a variety of output formats or devices. 'roff' input files contain text interspersed with instructions to control the formatter. Even in the absence of such instructions, GNU 'troff' still processes its input in several ways, by filling, hyphenating, breaking, and adjusting it, and supplementing it with inter-sentence space. * Menu: * Filling:: * Hyphenation:: * Sentences:: * Breaking:: * Adjustment:: * Tabs and Leaders:: * Requests and Macros:: * Macro Packages:: * Input Encodings:: * Input Conventions::  File: groff.info, Node: Filling, Next: Sentences, Prev: Text, Up: Text 5.1.1 Filling ------------- When GNU 'troff' starts up, it obtains information about the device for which it is preparing output.(1) (*note Filling-Footnote-1::) An essential property is the length of the output line, such as "6.5 inches". GNU 'troff' interprets plain text files employing the Unix line-ending convention. It reads input a character at a time, collecting words as it goes, and fits as many words together on an output line as it can--this is known as "filling". To GNU 'troff', a "word" is any sequence of one or more characters that aren't spaces or newlines. The exceptions separate words.(2) (*note Filling-Footnote-2::) To disable filling, see *note Manipulating Filling and Adjustment::. It is a truth universally acknowledged that a single man in possession of a good fortune must be in want of a wife. => It is a truth universally acknowledged that a => single man in possession of a good fortune must => be in want of a wife.  File: groff.info, Node: Filling-Footnotes, Up: Filling (1) *Note Device and Font Description Files::. (2) Tabs and leaders also separate words. Escape sequences can function as word characters, word separators, or neither--the last simply have no effect on GNU 'troff''s idea of whether an input character is within a word. We'll discuss all of these in due course.  File: groff.info, Node: Sentences, Next: Hyphenation, Prev: Filling, Up: Text 5.1.2 Sentences --------------- A passionate debate has raged for decades among writers of the English language over whether more space should appear between adjacent sentences than between words within a sentence, and if so, how much, and what other circumstances should influence this spacing.(1) (*note Sentences-Footnote-1::) GNU 'troff' follows the example of AT&T 'troff'; it attempts to detect the boundaries between sentences, and supplies additional inter-sentence space between them. Hello, world! Welcome to groff. => Hello, world! Welcome to groff. GNU 'troff' flags certain characters (normally '!', '?', and '.') as potentially ending a sentence. When GNU 'troff' encounters one of these "end-of-sentence characters" at the end of an input line, or one of them is followed by two (unescaped) spaces on the same input line, it appends an inter-word space followed by an inter-sentence space in the output. R. Harper subscribes to a maxim of P. T. Barnum. => R. Harper subscribes to a maxim of P. T. Barnum. In the above example, inter-sentence space is not added after 'P.' or 'T.' because the periods do not occur at the end of an input line, nor are they followed by two or more spaces. Let's imagine that we've heard something about defamation from Mr. Harper's attorney, recast the sentence, and reflowed it in our text editor. I submit that R. Harper subscribes to a maxim of P. T. Barnum. => I submit that R. Harper subscribes to a maxim of => P. T. Barnum. "Barnum" doesn't begin a sentence! What to do? Let us meet our first "escape sequence", a series of input characters that give instructions to GNU 'troff' instead of being used to construct output device glyphs.(2) (*note Sentences-Footnote-2::) An escape sequence begins with the backslash character '\' by default, an uncommon character in natural language text, and is _always_ followed by at least one other character, hence the term "sequence". The dummy character escape sequence '\&' can be used after an end-of-sentence character to defeat end-of-sentence detection on a per-instance basis. We can therefore rewrite our input more defensively. I submit that R.\& Harper subscribes to a maxim of P.\& T.\& Barnum. => I submit that R. Harper subscribes to a maxim of => P. T. Barnum. Adding text caused our input to wrap; now, we don't need '\&' after 'T.' but we do after 'P.'. Consistent use of the escape sequence ensures that potential sentence boundaries are robust to editing activities. Further advice along these lines will follow in *note Input Conventions::. Normally, the occurrence of a visible non-end-of-sentence character (as opposed to a space or tab) immediately after an end-of-sentence character cancels detection of the end of a sentence. For example, it would be incorrect for GNU 'troff' to infer the end of a sentence after the dot in '3.14159'. However, several characters are treated _transparently_ after the occurrence of an end-of-sentence character. That is, GNU 'troff' does not cancel end-of-sentence detection when it processes them. This is because such characters are often used as footnote markers or to close quotations and parentheticals. The default set is '"', ''', ')', ']', '*', '\[dg]', '\[dd]', '\[rq]', and '\[cq]'. The last four are examples of "special characters", escape sequences whose purpose is to obtain glyphs that are not easily typed at the keyboard, or which have special meaning to GNU 'troff' (like '\' itself).(3) (*note Sentences-Footnote-3::) \[lq]The idea that the poor should have leisure has always been shocking to the rich.\[rq] (Bertrand Russell, 1935) => "The idea that the poor should have => leisure has always been shocking to => the rich." (Bertrand Russell, 1935) The sets of characters that potentially end sentences or are transparent to sentence endings are configurable. See the 'cflags' request in *note Using Symbols::. To change the additional inter-sentence space amount--even to remove it entirely--see *note Manipulating Filling and Adjustment::.  File: groff.info, Node: Sentences-Footnotes, Up: Sentences (1) A well-researched jeremiad appreciated by 'groff' contributors on both sides of the sentence-spacing debate can be found at . (2) This statement oversimplifies; there are escape sequences whose purpose is precisely to produce glyphs on the output device, and input characters that _aren't_ part of escape sequences can undergo a great deal of processing before getting to the output. (3) The mnemonics for the special characters shown here are "dagger", "double dagger", "right (double) quote", and "closing (single) quote". See the 'groff_char(7)' man page.  File: groff.info, Node: Hyphenation, Next: Breaking, Prev: Sentences, Up: Text 5.1.3 Hyphenation ----------------- When an output line is nearly full, it is uncommon for the next word collected from the input to exactly fill it--typically, there is room left over only for part of the next word. The process of splitting a word so that it appears partially on one line (with a hyphen to indicate to the reader that the word has been broken) with its remainder on the next is "hyphenation". Hyphenation points can be manually specified; GNU 'troff' also uses a hyphenation algorithm and language-specific pattern files (based on those used in TeX) to decide which words can be hyphenated and where. Hyphenation does not always occur even when the hyphenation rules for a word allow it; it can be disabled, and when not disabled there are several parameters that can prevent it in certain circumstances. *Note Manipulating Hyphenation::.  File: groff.info, Node: Breaking, Next: Adjustment, Prev: Hyphenation, Up: Text 5.1.4 Breaking -------------- Once an output line is full, the next word (or remainder of a hyphenated one) is placed on a different output line; this is called a "break". In this manual and in 'roff' discussions generally, a "break" if not further qualified always refers to the termination of an output line. When the formatter is filling text, it introduces breaks automatically to keep output lines from exceeding the configured line length. After an automatic break, GNU 'troff' adjusts the line if applicable (see below), and then resumes collecting and filling text on the next output line. Sometimes, a line cannot be broken automatically. This usually does not happen with natural language text unless the output line length has been manipulated to be extremely short, but it can with specialized text like program source code. We can use 'perl' at the shell prompt to contrive an example of failure to break the line. We also employ the '-z' option to suppress normal output. $ perl -e 'print "#" x 80, "\n";' | nroff -z error-> warning: cannot break line The remedy for these cases is to tell GNU 'troff' where the line may be broken without hyphens. This is done with the non-printing break point escape sequence '\:'; see *note Manipulating Hyphenation::. What if the document author wants to stop filling lines temporarily, for instance to start a new paragraph? There are several solutions. A blank input line not only causes a break, but by default it also outputs a one-line vertical space (effectively a blank output line). This behavior can be modified; see *note Blank Line Traps::. Macro packages may discourage or disable the blank line method of paragraphing in favor of their own macros. A line that begins with one or more spaces causes a break. The spaces are output at the beginning of the next line without being _adjusted_ (see below); however, this behavior can be modified (*note Leading Space Traps::). Again, macro packages may provide other methods of producing indented paragraphs. Trailing spaces on text lines are discarded.(1) (*note Breaking-Footnote-1::) What if the file ends before enough words have been collected to fill an output line? Or the output line is exactly full but not yet broken, and there is no more input? GNU 'troff' interprets the end of input as a break. Certain requests also cause breaks, implicitly or explicitly. This is discussed in *note Manipulating Filling and Adjustment::.  File: groff.info, Node: Breaking-Footnotes, Up: Breaking (1) "Text lines" are defined in *note Requests and Macros::.  File: groff.info, Node: Adjustment, Next: Tabs and Leaders, Prev: Breaking, Up: Text 5.1.5 Adjustment ---------------- After GNU 'troff' performs an automatic break, it may then "adjust" the line, widening inter-word spaces until the text reaches the right margin. Extra spaces between words are preserved. Leading and trailing spaces are handled as noted above. Text can be aligned to the left or right margin only, or centered; see *note Manipulating Filling and Adjustment::.  File: groff.info, Node: Tabs and Leaders, Next: Input Conventions, Prev: Adjustment, Up: Text 5.1.6 Tabs and Leaders ---------------------- GNU 'troff' translates input horizontal tab characters ("tabs") and characters ("leaders") into movements to the next tab stop. Tabs simply move to the next tab stop; leaders place enough periods to fill the space. Tab stops are by default located every half inch measured from the drawing position corresponding to the beginning of the input line; see *note Page Geometry::. Tabs and leaders do not cause breaks and therefore do not interrupt filling. Below, we use arrows -> and bullets * to indicate input tabs and leaders, respectively. 1 -> 2 -> 3 * 4 -> * 5 => 1 2 3.......4 ........5 Tabs and leaders lend themselves to table construction.(1) (*note Tabs and Leaders-Footnote-1::) The tab and leader glyphs can be configured, and further facilities for sophisticated table composition are available; see *note Tabs and Fields::. There are many details to track when using such low-level features, so most users turn to the 'tbl(1)' preprocessor to lay out tables.  File: groff.info, Node: Tabs and Leaders-Footnotes, Up: Tabs and Leaders (1) "Tab" is short for "tabulation", revealing the term's origin as a spacing mechanism for table arrangement.  File: groff.info, Node: Requests and Macros, Next: Macro Packages, Prev: Tabs and Leaders, Up: Text 5.1.7 Requests and Macros ------------------------- We have now encountered almost all of the syntax there is in the 'roff' language, with an exception already noted in passing. A "request" is an instruction to the formatter that occurs after a "control character", which is recognized at the beginning of an input line. The regular control character is a dot ('.'). Its counterpart, the "no-break control character", a neutral apostrophe ('''), suppresses the break that is implied by some requests. These characters were chosen because it is uncommon for lines of text in natural languages to begin with them. If you require a formatted period or apostrophe (closing single quotation mark) where GNU 'troff' is expecting a control character, prefix the dot or neutral apostrophe with the dummy character escape sequence, '\&'. An input line beginning with a control character is called a "control line". Every line of input that is not a control line is a "text line".(1) (*note Requests and Macros-Footnote-1::) Requests often take "arguments", words (separated from the request name and each other by spaces) that specify details of the action GNU 'troff' is expected to perform. If a request is meaningless without arguments, it is typically ignored. GNU 'troff''s requests and escape sequences comprise the control language of the formatter. Of key importance are the requests that define macros. Macros are invoked like requests, enabling the request repertoire to be extended or overridden.(2) (*note Requests and Macros-Footnote-2::) A "macro" can be thought of as an abbreviation you can define for a collection of control and text lines. When the macro is "called" by giving its name after a control character, it is replaced with what it stands for. The process of textual replacement is known as "interpolation".(3) (*note Requests and Macros-Footnote-3::) Interpolations are handled as soon as they are recognized, and once performed, a 'roff' formatter scans the replacement for further requests, macro calls, and escape sequences. In 'roff' systems, the 'de' request defines a macro.(4) (*note Requests and Macros-Footnote-4::) .de DATE 2020-11-14 .. The foregoing input produces no output by itself; all we have done is store some information. Observe the pair of dots that ends the macro definition. This is a default; you can specify your own terminator for the macro definition as the second argument to the 'de' request. .de NAME ENDNAME Heywood Jabuzzoff .ENDNAME In fact, the ending marker is itself the name of a macro to be called, or a request to be invoked, if it is defined at the time its control line is read. .de END Big Rip .. .de START END Big Bang .END .START => Big Rip Big Bang In the foregoing example, "Big Rip" printed before "Big Bang" because its macro was _called_ first. Consider what would happen if we dropped 'END' from the '.de START' line and added '..' after '.END'. Would the order change? Let us consider a more elaborate example. .de DATE 2020-10-05 .. . .de BOSS D.\& Kruger, J.\& Peterman .. . .de NOTICE Approved: .DATE by .BOSS .. . Insert tedious regulatory compliance paragraph here. .NOTICE Insert tedious liability disclaimer paragraph here. .NOTICE => Insert tedious regulatory compliance paragraph here. => => Approved: 2020-10-05 by D. Kruger, J. Peterman => => Insert tedious liability disclaimer paragraph here. => => Approved: 2020-10-05 by D. Kruger, J. Peterman The above document started with a series of control lines. Three macros were defined, with a 'de' request declaring each macro's name, and the "body" of the macro starting on the next line and continuing until a line with two dots ''..'' marked its end. The text proper began only after the macros were defined; this is a common pattern. Only the 'NOTICE' macro was called "directly" by the document; 'DATE' and 'BOSS' were called only by 'NOTICE' itself. Escape sequences were used in 'BOSS', two levels of macro interpolation deep. The advantage in typing and maintenance economy may not be obvious from such a short example, but imagine a much longer document with dozens of such paragraphs, each requiring a notice of managerial approval. Consider what must happen if you are in charge of generating a new version of such a document with a different date, for a different boss. With well-chosen macros, you only have to change each datum in one place. In practice, we would probably use strings (*note Strings::) instead of macros for such simple interpolations; what is important here is to glimpse the potential of macros and the power of recursive interpolation. We could have defined 'DATE' and 'BOSS' in the opposite order; perhaps less obviously, we could also have defined them _after_ 'NOTICE'. "Forward references" like this are acceptable because the body of a macro definition is not (completely) interpreted, but stored instead (*note Copy Mode::). While a macro is being defined (or appended to), requests are not interpreted and macros not interpolated, whereas some commonly used escape sequences _are_ interpreted. 'roff' systems also support recursive macro calls, as long as you have a way to break the recursion (*note Conditionals and Loops::). Maintainable 'roff' documents tend to arrange macro definitions to minimize forward references.  File: groff.info, Node: Requests and Macros-Footnotes, Up: Requests and Macros (1) The '\' escape sequence can alter how an input line is classified; see *note Line Continuation::. (2) Argument handling in macros is more flexible but also more complex. *Note Calling Macros::. (3) Some escape sequences undergo interpolation as well. (4) GNU 'troff' offers additional ones. *Note Writing Macros::.  File: groff.info, Node: Macro Packages, Next: Input Encodings, Prev: Requests and Macros, Up: Text 5.1.8 Macro Packages -------------------- Macro definitions can be collected into "macro files", 'roff' input files designed to produce no output themselves but instead ease the preparation of other 'roff' documents. There is no syntactical difference between a macro file and any other 'roff' document; only its purpose distinguishes it. When a macro file is installed at a standard location and suitable for use by a general audience, it is often termed a "macro package".(1) (*note Macro Packages-Footnote-1::) Macro packages can be loaded by supplying the '-m' option to GNU 'troff' or a 'groff' front end. Alternatively, a document requiring a macro package can load it with the 'mso' ("macro source") request.  File: groff.info, Node: Macro Packages-Footnotes, Up: Macro Packages (1) Macro files and packages frequently define registers and strings as well.  File: groff.info, Node: Input Encodings, Next: Input Conventions, Prev: Macro Packages, Up: Text 5.1.9 Input Encodings --------------------- The 'groff' command's '-k' option calls the 'preconv' preprocessor to perform input character encoding conversions. Input to the GNU 'troff' formatter itself, on the other hand, must be in one of two encodings it can recognize. 'cp1047' The code page 1047 input encoding works only on EBCDIC platforms (and conversely, the other input encodings don't work with EBCDIC); the file 'cp1047.tmac' is loaded at startup. 'latin1' ISO Latin-1, an encoding for Western European languages, is the default input encoding on non-EBCDIC platforms; the file 'latin1.tmac' is loaded at startup. Any document that is encoded in ISO 646:1991 (a descendant of USAS X3.4-1968 or "US-ASCII"), or, equivalently, uses only code points from the "C0 Controls" and "Basic Latin" parts of the Unicode character set is also a valid ISO Latin-1 document; the standards are interchangeable in their first 128 code points.(1) (*note Input Encodings-Footnote-1::) Other encodings are supported by means of macro packages. 'latin2' To use ISO Latin-2, an encoding for Central and Eastern European languages, invoke '.mso latin2.tmac' at the beginning of your document or supply '-mlatin2' as a command-line argument to 'groff'. 'latin5' To use ISO Latin-5, an encoding for the Turkish language, invoke '.mso latin5.tmac' at the beginning of your document or supply '-mlatin5' as a command-line argument to 'groff'. 'latin9' ISO Latin-9 succeeds Latin-1; it includes a Euro sign and better glyph coverage for French. To use this encoding, invoke '.mso latin9.tmac' at the beginning of your document or supply '-mlatin9' as a command-line argument to 'groff'. Some characters from an input encoding may not be available with a particular output driver, or their glyphs may not have representation in the font used. For terminal devices, fallbacks are defined, like 'EUR' for the Euro sign and '(C)' for the copyright sign. For typesetter devices, you may need to "mount" fonts that support glyphs required by the document. *Note Font Positions::. Because a Euro glyph was not historically defined in PostScript fonts, 'groff' comes with a font called 'freeeuro.pfa' that provides the Euro in several styles. Standard PostScript fonts contain the glyphs from Latin-5 and Latin-9 that Latin-1 lacks, so these encodings are supported for the 'ps' and 'pdf' output devices as 'groff' ships, while Latin-2 is not. Unicode supports characters from all other input encodings; the 'utf8' output driver for terminals therefore does as well. The DVI output driver supports the Latin-2 and Latin-9 encodings if the command-line option '-mec' is used as well. (2) (*note Input Encodings-Footnote-2::)  File: groff.info, Node: Input Encodings-Footnotes, Up: Input Encodings (1) The _semantics_ of certain punctuation code points have gotten stricter with the successive standards, a cause of some frustration among man page writers; see the 'groff_char(7)' man page. (2) The DVI output device defaults to using the Computer Modern (CM) fonts; 'ec.tmac' loads the EC fonts instead, which provide Euro '\[Eu]' and per mille '\[%0]' glyphs.  File: groff.info, Node: Input Conventions, Prev: Input Encodings, Up: Text 5.1.10 Input Conventions ------------------------ Since GNU 'troff' fills text automatically, it is common practice in the 'roff' language to avoid visual composition of text in input files: the esthetic appeal of the formatted output is what matters. Therefore, 'roff' input should be arranged such that it is easy for authors and maintainers to compose and develop the document, understand the syntax of 'roff' requests, macro calls, and preprocessor languages used, and predict the behavior of the formatter. Several traditions have accrued in service of these goals. * Follow sentence endings in the input with newlines to ease their recognition (*note Sentences::). It is frequently convenient to end text lines after colons and semicolons as well, as these typically precede independent clauses. Consider doing so after commas; they often occur in lists that become easy to scan when itemized by line, or constitute supplements to the sentence that are added, deleted, or updated to clarify it. Parenthetical and quoted phrases are also good candidates for placement on text lines by themselves. * Set your text editor's line length to 72 characters or fewer.(1) (*note Input Conventions-Footnote-1::) This limit, combined with the previous item of advice, makes it less common that an input line will wrap in your text editor, and thus will help you perceive excessively long constructions in your text. Recall that natural languages originate in speech, not writing, and that punctuation is correlated with pauses for breathing and changes in prosody. * Use '\&' after '!', '?', and '.' if they are followed by space, tab, or newline characters and don't end a sentence. * In filled text lines, use '\&' before '.' and ''' if they are preceded by space, so that reflowing the input doesn't turn them into control lines. * Do not use spaces to perform indentation or align columns of a table. Leading spaces are reliable when text is not being filled. * Comment your document. It is never too soon to apply comments to record information of use to future document maintainers (including your future self). We thus introduce another escape sequence, '\"', which causes GNU 'troff' to ignore the remainder of the input line. * Use the empty request--a control character followed immediately by a newline--to visually manage separation of material in input files. Many of the 'groff' project's own documents use an empty request between sentences, after macro definitions, and where a break is expected, and two empty requests between paragraphs or other requests or macro calls that will introduce vertical space into the document. You can combine the empty request with the comment escape sequence to include whole-line comments in your document, and even "comment out" sections of it. We conclude this section with an example sufficiently long to illustrate most of the above suggestions in practice. For the purpose of fitting the example between the margins of this manual with the font used for its typeset version, we have shortened the input line length to 56 columns. As before, an arrow -> indicates a tab character. .\" nroff this_file.roff | less .\" groff -T ps this_file.roff > this_file.ps ->The theory of relativity is intimately connected with the theory of space and time. . I shall therefore begin with a brief investigation of the origin of our ideas of space and time, although in doing so I know that I introduce a controversial subject. \" remainder of paragraph elided . . ->The experiences of an individual appear to us arranged in a series of events; in this series the single events which we remember appear to be ordered according to the criterion of \[lq]earlier\[rq] and \[lq]later\[rq], \" punct swapped which cannot be analysed further. . There exists, therefore, for the individual, an I-time, or subjective time. . This itself is not measurable. . I can, indeed, associate numbers with the events, in such a way that the greater number is associated with the later event than with an earlier one; but the nature of this association may be quite arbitrary. . This association I can define by means of a clock by comparing the order of events furnished by the clock with the order of a given series of events. . We understand by a clock something which provides a series of events which can be counted, and which has other properties of which we shall speak later. .\" Albert Einstein, _The Meaning of Relativity_, 1922  File: groff.info, Node: Input Conventions-Footnotes, Up: Input Conventions (1) Emacs: 'fill-column: 72'; Vim: 'textwidth=72'  File: groff.info, Node: Page Geometry, Next: Measurements, Prev: Text, Up: GNU troff Reference 5.2 Page Geometry ================= 'roff' systems format text under certain assumptions about the size of the output medium, or page. For the formatter to correctly break a line it is filling, it must know the line length, which it derives from the page width (*note Line Layout::). For it to decide whether to write an output line to the current page or wait until the next one, it must know the page length (*note Page Layout::). A device's "resolution" converts practical units like inches or centimeters to "basic units", a convenient length measure for the output device or file format. The formatter and output driver use basic units to reckon page measurements. The device description file defines its resolution and page dimensions (*note DESC File Format::). A "page" is a two-dimensional structure upon which a 'roff' system imposes a rectangular coordinate system with its upper left corner as the origin. Coordinate values are in basic units and increase down and to the right. Useful ones are therefore always positive and within numeric ranges corresponding to the page boundaries. While the formatter (and, later, output driver) is processing a page, it keeps track of its "drawing position", which is the location at which the next glyph will be written, from which the next motion will be measured, or where a geometric object will commence rendering. Notionally, glyphs are drawn from the text baseline upward and to the right.(1) (*note Page Geometry-Footnote-1::) The "text baseline" is a (usually invisible) line upon which the glyphs of a typeface are aligned. A glyph therefore "starts" at its bottom-left corner. If drawn at the origin, a typical letter glyph would lie partially or wholly off the page, depending on whether, like "g", it features a descender below the baseline. Such a situation is nearly always undesirable. It is furthermore conventional not to write or draw at the extreme edges of the page. Therefore the initial drawing position of a 'roff' formatter is not at the origin, but below and to the right of it. This rightward shift from the left edge is known as the "page offset".(2) (*note Page Geometry-Footnote-2::) The downward shift leaves room for a text output line. Text is arranged on a one-dimensional lattice of text baselines from the top to the bottom of the page. "Vertical spacing" is the distance between adjacent text baselines. Typographic tradition sets this quantity to 120% of the type size. The initial drawing position is one unit of vertical spacing below the page top. Typographers term this unit a vee. Vertical spacing has an impact on page-breaking decisions. Generally, when a break occurs, the formatter moves the drawing position to the next text baseline automatically. If the formatter were already writing to the last line that would fit on the page, advancing by one vee would place the next text baseline off the page. Rather than let that happen, 'roff' formatters instruct the output driver to eject the page, start a new one, and again set the drawing position to one vee below the page top; this is a "page break". When the last line of input text corresponds to the last output line that fits on the page, the break caused by the end of input will also break the page, producing a useless blank one. Macro packages keep users from having to confront this difficulty by setting "traps" (*note Traps::); moreover, all but the simplest page layouts tend to have headers and footers, or at least bear vertical margins larger than one vee.  File: groff.info, Node: Page Geometry-Footnotes, Up: Page Geometry (1) 'groff' does not yet support right-to-left scripts. (2) 'groff''s terminal output devices have page offsets of zero.  File: groff.info, Node: Measurements, Next: Numeric Expressions, Prev: Text, Up: GNU troff Reference 5.3 Measurements ================ The formatter sometimes requires the input of numeric parameters to specify measurements. These are specified as integers or decimal fractions with an optional "scaling unit" suffixed. A scaling unit is a letter that immediately follows the last digit of a number. Digits after the decimal point are optional. Measurement expressions include '10.5p', '11i', and '3.c'. Measurements are scaled by the scaling unit and stored internally (with any fractional part discarded) in basic units. The device resolution can therefore be obtained by storing a value of '1i' to a register. The only constraint on the basic unit is that it is at least as small as any other unit. 'u' Basic unit. 'i' Inch; defined as 2.54 centimeters. 'c' Centimeter; a centimeter is about 0.3937 inches. 'p' Point; a typesetter's unit used for measuring type size. There are 72 points to an inch. 'P' Pica; another typesetter's unit. There are 6 picas to an inch and 12 points to a pica. 's' 'z' *Note Using Fractional Type Sizes::, for a discussion of these units. 'f' GNU 'troff' defines this unit to scale decimal fractions in the interval [0, 1] to 16-bit unsigned integers. It multiplies a quantity by 65,536. *Note Colors::, for usage. The magnitudes of other scaling units depend on the text formatting parameters in effect. These are useful when specifying measurements that need to scale with the typeface or vertical spacing. 'm' Em; an em is equal to the current type size in points. It is named thus because it is approximately the width of the letter 'M'. 'n' En; an en is one-half em. 'v' Vee; recall *note Page Geometry::. 'M' Hundredth of an em. * Menu: * Motion Quanta:: * Default Units::  File: groff.info, Node: Motion Quanta, Next: Default Units, Prev: Measurements, Up: Measurements 5.3.1 Motion Quanta ------------------- An output device's basic unit 'u' is not necessarily its smallest addressable length; 'u' can be smaller to avoid problems with integer roundoff. The minimum distances that a device can work with in the horizontal and vertical directions are termed its "motion quanta". Measurements are rounded to applicable motion quanta. Half-quantum fractions round toward zero. -- Register: \n[.H] -- Register: \n[.V] These read-only registers interpolate the horizontal and vertical motion quanta, respectively, of the output device in basic units. For example, we might draw short baseline rules on a terminal device as follows. *Note Drawing Geometric Objects::. .tm \n[.H] error-> 24 .nf \l'36u' 36u \l'37u' 37u => _ 36u => __ 37u  File: groff.info, Node: Default Units, Prev: Motion Quanta, Up: Measurements 5.3.2 Default Units ------------------- A general-purpose register (one created or updated with the 'nr' request; see *note Registers::) is implicitly dimensionless, or reckoned in basic units if interpreted in a measurement context. But it is convenient for many requests and escape sequences to infer a scaling unit for an argument if none is specified. An explicit scaling unit (not after a closing parenthesis) can override an undesirable default. Effectively, the default unit is suffixed to the expression if a scaling unit is not already present. GNU 'troff''s use of integer arithmetic should also be kept in mind (*note Numeric Expressions::). The 'll' request interprets its argument in ems by default. Consider several attempts to set a line length of 3.5 inches when the type size is 10 points on a terminal device with a resolution of 240 basic units and horizontal motion quantum of 24. Some expressions become zero; the request clamps them to that quantum. .ll 3.5i \" 3.5i (= 840u) .ll 7/2 \" 7u/2u -> 3u -> 3m -> 0, clamped to 24u .ll (7 / 2)u \" 7u/2u -> as above .ll 7/2i \" 7u/2i -> 7u/480u -> 0 -> as above .ll 7i/2 \" 7i/2u -> 1680u/2m -> 1680u/24u -> 35u .ll 7i/2u \" 3.5i (= 840u) The safest way to specify measurements is to attach a scaling unit. To multiply or divide by a dimensionless quantity, use 'u' as its scaling unit.  File: groff.info, Node: Numeric Expressions, Next: Identifiers, Prev: Measurements, Up: GNU troff Reference 5.4 Numeric Expressions ======================= A "numeric expression" evaluates to an integer: it can be as simple as a literal '0' or it can be a complex sequence of register and string interpolations interleaved with measurements and operators. GNU 'troff' provides a set of mathematical and logical operators familiar to programmers--as well as some unusual ones--but supports only integer arithmetic.(1) (*note Numeric Expressions-Footnote-1::) The internal data type used for computing results is usually a 32-bit signed integer, which suffices to represent magnitudes within a range of ±2 billion.(2) (*note Numeric Expressions-Footnote-2::) Arithmetic infix operators perform a function on the numeric expressions to their left and right; they are '+' (addition), '-' (subtraction), '*' (multiplication), '/' (truncating division), and '%' (modulus). "Truncating division" rounds to the integer nearer to zero, no matter how large the fractional portion. Overflow and division (or modulus) by zero are errors and abort evaluation of a numeric expression. Arithmetic unary operators operate on the numeric expression to their right; they are '-' (negation) and '+' (assertion--for completeness; it does nothing). The unary minus must often be used with parentheses to avoid confusion with the decrementation operator, discussed below. Observe the rounding behavior and effect of negative operands on the modulus and truncating division operators. .nr T 199/100 .nr U 5/2 .nr V (-5)/2 .nr W 5/-2 .nr X 5%2 .nr Y (-5)%2 .nr Z 5%-2 T=\n[T] U=\n[U] V=\n[V] W=\n[W] X=\n[X] Y=\n[Y] Z=\n[Z] => T=1 U=2 V=-2 W=-2 X=1 Y=-1 Z=1 The sign of the modulus of operands of mixed signs is determined by the sign of the first. Division and modulus operators satisfy the following property: given a dividend A and a divisor B, a quotient Q formed by '(a / b)' and a remainder R by '(a % b)', then qb + r = a. GNU 'troff''s scaling operator, used with parentheses as '(C;E)', evaluates a numeric expression E using C as the default scaling unit. If C is omitted, scaling units are ignored in the evaluation of E. This operator can save typing by avoiding the attachment of scaling units to every operand out of caution. Your macros can select a sensible default unit in case the user neglects to supply one. .\" Indent by amount given in first argument; assume ens. .de Indent . in (n;\\$1) .. Without the scaling operator, the foregoing macro would, if called with a unitless argument, cause indentation by the 'in' request's default scaling unit (ems). The result would be twice as much indentation as expected. GNU 'troff' also provides a pair of operators to compute the extrema of two operands: '>?' (maximum) and ' Looks like we'll end up paying 3 salaries. Comparison operators comprise '<' (less than), '>' (greater than), '<=' (less than or equal), '>=' (greater than or equal), and '=' (equal). '==' is a synonym for '='. When evaluated, a comparison is replaced with '0' if it is false and '1' if true. In the 'roff' language, positive values are true, others false. We can operate on truth values with the logical operators '&' (logical conjunction or "and") and ':' (logical disjunction or "or"). They evaluate as comparison operators do. A logical complementation ("not") operator, '!', works only within 'if', 'ie', and 'while' requests. Furthermore, '!' is recognized only at the beginning of a numeric expression not contained by another numeric expression. In other words, it must be the "outermost" operator. Including it elsewhere in the expression produces a warning in the 'number' category (*note Warnings::), and its expression evaluates false. This unfortunate limitation maintains compatibility with AT&T 'troff'. Test a numeric expression for falsity by comparing it to a false value.(3) (*note Numeric Expressions-Footnote-3::) .nr X 1 .nr Y 0 .\" This does not work as expected. .if (\n[X])&(!\n[Y]) .nop A: X is true, Y is false . .\" Use this construct instead. .if (\n[X])&(\n[Y]<=0) .nop B: X is true, Y is false error-> warning: expected numeric expression, got '!' => B: X is true, Y is false The 'roff' language has no operator precedence: expressions are evaluated strictly from left to right, in contrast to schoolhouse arithmetic. Use parentheses '(' ')' to impose a desired precedence upon subexpressions. .nr X 3+5*4 .nr Y (3+5)*4 .nr Z 3+(5*4) X=\n[X] Y=\n[Y] Z=\n[Z] => X=32 Y=32 Z=23 For many requests and escape sequences that cause motion on the page, the unary operators '+' and '-' work differently when leading a numeric expression. They then indicate a motion relative to the drawing position: positive is down in vertical contexts, right in horizontal ones. '+' and '-' are also treated differently by the following requests and escape sequences: 'bp', 'in', 'll', 'lt', 'nm', 'nr', 'pl', 'pn', 'po', 'ps', 'pvs', 'rt', 'ti', '\H', '\R', and '\s'. Here, leading plus and minus signs serve as incrementation and decrementation operators, respectively. To negate an expression, subtract it from zero or include the unary minus in parentheses with its argument. *Note Setting Registers::, for examples. A leading '|' operator indicates a motion relative not to the drawing position but to a boundary. For horizontal motions, the measurement specifies a distance relative to a drawing position corresponding to the beginning of the _input_ line. By default, tab stops reckon movements in this way. Most escape sequences do not; '|' tells them to do so. Mind the \h'1.2i'gap. .br Mind the \h'|1.2i'gap. .br Mind the \h'|1.2i'gap. => Mind the gap. => Mind the gap. => Mind the gap. One use of this feature is to define macros whose scope is limited to the output they format. .\" underline word $1 with trailing punctuation $2 .de Underline . nop \\$1\l'|0\[ul]'\\$2 .. Typographical emphasis is best used .Underline sparingly . In the above example, '|0' specifies a negative motion from the current position (at the end of the argument just emitted, '\$1') to the beginning of the input line. Thus, the '\l' escape sequence in this case draws a line from right to left. A macro call occurs at the beginning of an input line;(4) (*note Numeric Expressions-Footnote-4::) if the '|' operator were omitted, then the underline would be drawn at zero distance from the current position, producing device-dependent, and likely undesirable, results. On the 'ps' output device, it underlines the period. For vertical motions, the '|' operator specifies a distance from the first text baseline on the page or in the current diversion,(5) (*note Numeric Expressions-Footnote-5::) using the current vertical spacing. A .br B \Z'C'\v'|0'D => A D => B C In the foregoing example, we've used the '\Z' escape sequence (*note Page Motions::) to restore the drawing position after formatting 'C', then moved vertically to the first text baseline on the page. -- Escape sequence: \B'anything' Interpolate 1 if ANYTHING is a valid numeric expression, and 0 otherwise. The delimiter need not be a neutral apostrophe; see *note Delimiters::. You might use '\B' along with the 'if' request to filter out invalid macro or string arguments. *Note Conditionals and Loops::. .\" Indent by amount given in first argument; assume ens. .de Indent . if \B'\\$1' .in (n;\\$1) .. A register interpolated as an operand in a numeric expression must have an Arabic format; luckily, this is the default. *Note Assigning Register Formats::. Because spaces separate arguments to requests, spaces are not allowed in numeric expressions unless the (sub)expression containing them is surrounded by parentheses. *Note Invoking Requests::, and *note Conditionals and Loops::. .nf .nr a 1+2 + 2+1 \na error-> expected numeric expression, got a space => 3 .nr a 1+(2 + 2)+1 \na => 6 The 'nr' request (*note Setting Registers::) expects its second and optional third arguments to be numeric expressions; a bare '+' does not qualify, so our first attempt got a warning.  File: groff.info, Node: Numeric Expressions-Footnotes, Up: Numeric Expressions (1) Provision is made for interpreting and reporting decimal fractions in certain cases. (2) If that's not enough, see the 'groff_tmac(5)' man page for the '62bit.tmac' macro package. (3) *Note Conditionals and Loops::. (4) Control structure syntax creates an exception to this rule, but is designed to remain useful: recalling our example, '.if 1 .Underline this' would underline only "this", precisely. *Note Conditionals and Loops::. (5) *Note Diversions::.  File: groff.info, Node: Identifiers, Next: Formatter Instructions, Prev: Numeric Expressions, Up: GNU troff Reference 5.5 Identifiers =============== An "identifier" labels a GNU 'troff' datum such as a register, name (macro, string, or diversion), typeface, color, special character, character class, environment, or stream. Valid identifiers consist of one or more ordinary characters. An ordinary character is an input character that is not the escape character, a leader, tab, newline, or invalid as GNU 'troff' input. Invalid input characters are a subset of control characters (from the sets "C0 Controls" and "C1 Controls" as Unicode describes them). When GNU 'troff' encounters one in an identifier, it produces a warning in category 'input' (*note Warnings::). They are removed during interpretation: an identifier 'foo', followed by an invalid character and then 'bar', is processed as 'foobar'. On a machine using the ISO 646, 8859, or 10646 character encodings, invalid input characters are '0x00', '0x08', '0x0B', '0x0D'-'0x1F', and '0x80'-'0x9F'. On an EBCDIC host, they are '0x00'-'0x01', '0x08', '0x09', '0x0B', '0x0D'-'0x14', '0x17'-'0x1F', and '0x30'-'0x3F'.(1) (*note Identifiers-Footnote-1::) Some of these code points are used by GNU 'troff' internally, making it non-trivial to extend the program to accept UTF-8 or other encodings that use characters from these ranges.(2) (*note Identifiers-Footnote-2::) Thus, the identifiers 'br', 'PP', 'end-list', 'ref*normal-print', '|', '@_', and '!"#$%'()*+,-./' are all valid. Discretion should be exercised to prevent confusion. Identifiers starting with '(' or '[' require care. .nr x 9 .nr y 1 .nr (x 2 .nr [y 3 .nr sum1 (\n(x + \n[y]) error-> a space character is not allowed in an escape error-> sequence parameter A:2+3=\n[sum1] .nr sum2 (\n((x + \n[[y]) B:2+3=\n[sum2] .nr sum3 (\n[(x] + \n([y) C:2+3=\n[sum3] => A:2+3=1 B:2+3=5 C:2+3=5 An identifier with a closing bracket (']') in its name can't be accessed with bracket-form escape sequences that expect an identifier as a parameter. For example, '\[foo]]' accesses the glyph 'foo', followed by ']' in whatever the surrounding context is, whereas '\C'foo]'' formats a glyph named 'foo]'. Similarly, the identifier '(' can't be interpolated _except_ with bracket forms. If you begin a macro, string, or diversion name with either of the characters '[' or ']', you foreclose use of the 'grefer' preprocessor, which recognizes '.[' and '.]' as bibliographic reference delimiters. -- Escape sequence: \A'anything' Interpolate 1 if ANYTHING is a valid identifier, and 0 otherwise. The delimiter need not be a neutral apostrophe; see *note Delimiters::. Because invalid input characters are removed (see above), invalid identifiers are empty or contain spaces, tabs, or newlines. You can employ '\A' to validate a macro argument before using it to construct another escape sequence or identifier. .\" usage: .init-coordinate-pair name val1 val2 .\" Create a coordinate pair where name!x=val1 and .\" name!y=val2. .de init-coordinate-pair . if \A'\\$1' \{\ . if \B'\\$2' .nr \\$1!x \\$2 . if \B'\\$3' .nr \\$1!y \\$3 . \} .. .init-coordinate-pair center 5 10 The center is at (\n[center!x], \n[center!y]). .init-coordinate-pair "poi->nt" trash garbage \" ignored .init-coordinate-pair point trash garbage \" ignored => The center is at (5, 10). In this example, we also validated the numeric arguments; the registers 'point!x' and 'point!y' remain undefined. *Note Numeric Expressions:: for the '\B' escape sequence. How GNU 'troff' handles the interpretation of an undefined identifier depends on the context. There is no way to invoke an undefined request; such syntax is interpreted as a macro call instead. If the identifier is interpreted as a string, macro, or diversion, GNU 'troff' emits a warning in category 'mac', defines it as empty, and interpolates nothing. If the identifier is interpreted as a register, GNU 'troff' emits a warning in category 'reg', initializes it to zero, and interpolates that value. *Note Warnings::, *note Interpolating Registers::, and *note Strings::. Attempting to use an undefined typeface, special character, color, character class, environment, or stream generally provokes an error diagnostic. Identifiers for requests, macros, strings, and diversions share one name space; special characters and character classes another. No other object types do. .de xxx . nop foo .. .di xxx bar .br .di . .xxx => bar The foregoing example shows that GNU 'troff' reuses the identifier 'xxx', changing it from a macro to a diversion. No warning is emitted, and the previous contents of 'xxx' are lost.  File: groff.info, Node: Identifiers-Footnotes, Up: Identifiers (1) Historically, control characters like ASCII STX, ETX, and BEL (, , and ) have been observed in 'roff' documents, particularly in macro packages employing them as delimiters with the output comparison operator to try to avoid collisions with the content of arbitrary user-supplied parameters (*note Operators in Conditionals::). We discourage this expedient; in GNU 'troff' it is unnecessary (outside of compatibility mode) because delimited arguments are parsed at a different input level than the surrounding context. *Note Implementation Differences::. (2) Consider what happens when a C1 control '0x80'-'0x9F' is necessary as a continuation byte in a UTF-8 sequence.  File: groff.info, Node: Formatter Instructions, Next: Registers, Prev: Identifiers, Up: GNU troff Reference 5.6 Formatter Instructions ========================== To support documents that require more than filling, automatic line breaking and hyphenation, adjustment, and supplemental inter-sentence space, the 'roff' language offers two means of embedding instructions to the formatter. One is a "request", which begins with a control character and takes up the remainder of the input line. Requests often perform relatively large-scale operations such as setting the page length, breaking the line, or starting a new page. They also conduct internal operations like defining macros. The other is an "escape sequence", which begins with the escape character and can be embedded anywhere in the input, even in arguments to requests and other escape sequences. Escape sequences interpolate special characters, strings, or registers, and handle comparatively minor formatting tasks like sub- and superscripting. Some operations, such as font selection and type size alteration, are available via both requests and escape sequences. * Menu: * Control Characters:: * Invoking Requests:: * Calling Macros:: * Using Escape Sequences:: * Delimiters::  File: groff.info, Node: Control Characters, Next: Invoking Requests, Prev: Formatter Instructions, Up: Formatter Instructions 5.6.1 Control Characters ------------------------ The mechanism of using 'roff''s control characters to invoke requests and call macros was introduced in *note Requests and Macros::. Control characters are recognized only at the beginning of an input line, or at the beginning of the branch of a control structure request; see *note Conditionals and Loops::. A few requests cause a break implicitly; use the no-break control character to prevent the break. Break suppression is its sole behavioral distinction. Employing the no-break control character to invoke requests that don't cause breaks is harmless but poor style. *Note Manipulating Filling and Adjustment::. The control '.' and no-break control ''' characters can each be changed to any ordinary character(1) (*note Control Characters-Footnote-1::) with the 'cc' and 'c2' requests, respectively. -- Request: .cc [o] Recognize the ordinary character O as the control character. If O is absent or invalid, the default control character '.' is selected. The identity of the control character is associated with the environment (*note Environments::). -- Request: .c2 [o] Recognize the ordinary character O as the no-break control character. If O is absent or invalid, the default no-break control character ''' is selected. The identity of the no-break control character is associated with the environment (*note Environments::). When writing a macro, you might wish to know which control character was used to call it. -- Register: \n[.br] This read-only register interpolates 1 if the currently executing macro was called using the normal control character and 0 otherwise. If a macro is interpolated as a string, the '.br' register's value is inherited from the context of the string interpolation. *Note Strings::. Use this register to reliably intercept requests that imply breaks. .als bp*orig bp .de bp . ie \\n[.br] .bp*orig . el 'bp*orig .. Testing the '.br' register outside of a macro definition makes no sense.  File: groff.info, Node: Control Characters-Footnotes, Up: Control Characters (1) Recall *note Identifiers::.  File: groff.info, Node: Invoking Requests, Next: Calling Macros, Prev: Control Characters, Up: Formatter Instructions 5.6.2 Invoking Requests ----------------------- A control character is optionally followed by tabs and/or spaces and then an identifier naming a request or macro. The invocation of an unrecognized request is interpreted as a macro call. Defining a macro with the same name as a request replaces the request. Deleting a request name with the 'rm' request makes it unavailable. The 'als' request can alias requests, permitting them to be wrapped or non-destructively replaced. *Note Strings::. There is no inherent limit on argument length or quantity. Most requests take one or more arguments, and ignore any they do not expect. A request may be separated from its arguments by tabs or spaces, but only spaces can separate an argument from its successor. Only one between arguments is necessary; any excess is ignored. GNU 'troff' does not allow tabs for argument separation.(1) (*note Invoking Requests-Footnote-1::) Generally, a space _within_ a request argument is not relevant, not meaningful, or is supported by bespoke provisions, as with the 'tl' request's delimiters (*note Page Layout::). Some requests, like 'ds', interpret the remainder of the control line as a single argument. *Note Strings::. Spaces and tabs immediately after a control character are ignored. Commonly, authors structure the source of documents or macro files with them. .de center . if \\n[.br] \ . br . ce \\$1 .. . . .de right-align .->if \\n[.br] \ .->->br .->rj \\$1 .. If you assign an empty blank line trap, you can separate macro definitions (or any input lines) with blank lines. .de do-nothing .. .blm do-nothing \" activate blank line trap .de center . if \\n[.br] \ . br . ce \\$1 .. .de right-align .->if \\n[.br] \ .->->br .->rj \\$1 .. .blm \" deactivate blank line trap *Note Blank Line Traps::.  File: groff.info, Node: Invoking Requests-Footnotes, Up: Invoking Requests (1) In compatibility mode, a space is not necessary after a request or macro name of two characters' length. Also, Plan 9 'troff' allows tabs to separate arguments.  File: groff.info, Node: Calling Macros, Next: Using Escape Sequences, Prev: Invoking Requests, Up: Formatter Instructions 5.6.3 Calling Macros -------------------- If a macro of the desired name does not exist when called, it is created, assigned an empty definition, and a warning in category 'mac' is emitted. Calling an undefined macro _does_ end a macro definition naming it as its end macro (*note Writing Macros::). To embed spaces _within_ a macro argument, enclose the argument in neutral double quotes '"'. Horizontal motion escape sequences are sometimes a better choice for arguments to be formatted as text. Consider calls to a hypothetical section heading macro 'uh'. .uh The Mouse Problem .uh "The Mouse Problem" .uh The\~Mouse\~Problem .uh The\ Mouse\ Problem The first line calls 'uh' with three arguments: 'The', 'Mouse', and 'Problem'. The remainder call the 'uh' macro with one argument, 'The Mouse Problem'. The last solution, using escaped spaces, can be found in documents prepared for AT&T 'troff'. It can cause surprise when text is adjusted, because '\' inserts a _fixed-width_, non-breaking space. GNU 'troff''s '\~' escape sequence inserts an adjustable, non-breaking space.(1) (*note Calling Macros-Footnote-1::) The foregoing raises the question of how to embed neutral double quotes or backslashes in macro arguments when _those_ characters are desired as literals. In GNU 'troff', the special character escape sequence '\[rs]' produces a backslash and '\[dq]' a neutral double quote. In GNU 'troff''s AT&T compatibility mode, these characters remain available as '\(rs' and '\(dq', respectively. AT&T 'troff' did not consistently define these special characters, but its descendants can be made to support them. *Note Device and Font Description Files::. If even that is not feasible, options remain. To obtain a literal escape character in a macro argument, you can simply type it if you change or disable the escape character first. *Note Using Escape Sequences::. Otherwise, you must escape the escape character repeatedly to a context-dependent extent. *Note Copy Mode::. For the (neutral) double quote, you have recourse to an obscure syntactical feature of AT&T 'troff'. Because a double quote can begin a macro argument, the formatter keeps track of whether the current argument was started thus, and doesn't require a space after the double quote that ends it.(2) (*note Calling Macros-Footnote-2::) In the argument list to a macro, a double quote that _isn't_ preceded by a space _doesn't_ start a macro argument. If not preceded by a double quote that began an argument, this double quote becomes part of the argument. Furthermore, within a quoted argument, a pair of adjacent double quotes becomes a literal double quote. .de eq . tm arg1:\\$1 arg2:\\$2 arg3:\\$3 . tm arg4:\\$4 arg5:\\$5 arg6:\\$6 .. \" 4 backslashes on the next line .eq a" "b c" "de"f\\\\g" h""i "j""k" error-> arg1:a" arg2:b c arg3:de error-> arg4:f\g" arg5:h""i arg6:j"k Apart from the complexity of the rules, this traditional solution has the disadvantage that double quotes don't survive repeated argument expansion in AT&T 'troff' or GNU 'troff''s compatibility mode. This can frustrate efforts to pass such arguments intact through multiple macro calls. .cp 1 .de eq . tm arg1:\\$1 arg2:\\$2 arg3:\\$3 . tm arg4:\\$4 arg5:\\$5 arg6:\\$6 .. .de xe . eq \\$1 \\$2 \\$3 \\$4 \\$5 \\$6 .. \" 8 backslashes on the next line .xe a" "b c" "de"f\\\\\\\\g" h""i "j""k" error-> arg1:a" arg2:b arg3:c error-> arg4:de arg5:f\g" arg6:h""i Outside of compatibility mode, GNU 'troff' doesn't exhibit this problem because it tracks the nesting depth of interpolations. *Note Implementation Differences::.  File: groff.info, Node: Calling Macros-Footnotes, Up: Calling Macros (1) '\~' is fairly portable; see *note Other Differences::. (2) Strictly, you can neglect to close the last quoted macro argument, relying on the end of the control line to do so. We consider this lethargic practice poor style.  File: groff.info, Node: Using Escape Sequences, Next: Delimiters, Prev: Calling Macros, Up: Formatter Instructions 5.6.4 Using Escape Sequences ---------------------------- Whereas requests must occur on control lines, escape sequences can occur intermixed with text and may appear in arguments to requests, macros, and other escape sequences. An escape sequence is introduced by the escape character, a backslash '\' (but see the 'ec' request below). The next character selects the escape's function. Escape sequences vary in length. Some take an argument, and of those, some have different syntactical forms for a one-character, two-character, or arbitrary-length argument. Others accept _only_ an arbitrary-length argument. In the former scheme, a one-character argument follows the function character immediately, an opening parenthesis '(' introduces a two-character argument (no closing parenthesis is used), and an argument of arbitrary length is enclosed in brackets '[]'. In the latter scheme, the user selects a delimiter character. A few escape sequences are idiosyncratic, and support both of the foregoing conventions ('\s'), designate their own termination sequence ('\?'), consume input until the next newline ('\!', '\"', '\#'), or support an additional modifier character ('\s' again, and '\n'). As with requests, use of some escape sequences in source documents may interact poorly with a macro package you use; consult its documentation to learn of "safe" sequences or alternative facilities it provides to achieve the desired result. If an escape character is followed by a character that does not identify a defined operation, the escape character is ignored (producing a diagnostic of the 'escape' warning category, which is not enabled by default) and the following character is processed normally. $ groff -Tps -ww .nr N 12 .ds co white .ds animal elephant I have \fI\nN \*(co \*[animal]s,\f[] said \P.\&\~Pseudo Pachyderm. error-> warning: escape character ignored before 'P' => I have 12 white elephants, said P. Pseudo Pachyderm. Escape sequence interpolation is of higher precedence than escape sequence argument interpretation. This rule affords flexibility in using escape sequences to construct parameters to other escape sequences. .ds family C\" Courier .ds style I\" oblique Choice a typeface \f(\*[family]\*[style]wisely. => Choose a typeface wisely. In the above, the syntax form '\f(' accepts only two characters for an argument; the example works because the subsequent escape sequences are interpolated before the selection escape sequence argument is processed, and strings 'family' and 'style' interpolate one character each.(1) (*note Using Escape Sequences-Footnote-1::) The escape character is nearly always interpreted when encountered; it is therefore desirable to have a way to interpolate it, disable it, or change it. -- Escape sequence: \e Interpolate the escape character. The '\[rs]' special character escape sequence formats a backslash glyph. In macro and string definitions, the input sequences '\\' and '\E' defer interpretation of escape sequences. *Note Copy Mode::. -- Request: .eo Disable the escape mechanism except in copy mode. Once this request is invoked, no input character is recognized as starting an escape sequence in interpretation mode. -- Request: .ec [o] Recognize the ordinary character O as the escape character. If O is absent or invalid, the default escape character '\' is selected. Switching escape sequence interpretation off to define a macro and back on afterward can obviate the need to double the escape character within the definition. *Note Writing Macros::. This technique is not available if your macro needs to interpolate values at the time it is _defined_--but many do not. .\" simplified `BR` macro from the man(7) macro package .eo .de BR . ds result \& . while (\n[.$] >= 2) \{\ . as result \fB\$1\fR\$2\" . shift 2 . \} . if \n[.$] .as result \fB\$1\" \*[result] . rm result . ft R .. .ec -- Request: .ecs -- Request: .ecr The 'ecs' request stores the escape character for recall with 'ecr'. 'ecr' sets the escape character to '\' if none has been saved. Use these requests together to temporarily change the escape character. Using a different escape character, or disabling it, when calling macros not under your control will likely cause errors, since GNU 'troff' has no mechanism to "intern" macros--that is, to convert a macro definition into a form independent of its representation.(2) (*note Using Escape Sequences-Footnote-2::) When a macro is called, its contents are interpreted literally.  File: groff.info, Node: Using Escape Sequences-Footnotes, Up: Using Escape Sequences (1) The omission of spaces before the comment escape sequences is necessary; see *note Strings::. (2) TeX does have such a mechanism.  File: groff.info, Node: Delimiters, Prev: Using Escape Sequences, Up: Formatter Instructions 5.6.5 Delimiters ---------------- Some escape sequences that require parameters use delimiters. The neutral apostrophe ''' is a popular choice and shown in this document. The neutral double quote '"' is also commonly seen. Letters, numerals, and leaders can be used. Punctuation characters are likely better choices, except for those defined as infix operators in numeric expressions; see below. \l'1.5i\[bu]' \" draw 1.5 inches of bullet glyphs The following escape sequences don't take arguments and thus are allowed as delimiters: '\', '\%', '\|', '\^', '\{', '\}', '\'', '\`', '\-', '\_', '\!', '\?', '\)', '\/', '\,', '\&', '\:', '\~', '\0', '\a', '\c', '\d', '\e', '\E', '\p', '\r', '\t', and '\u'. However, using them this way is discouraged; they can make the input confusing to read. A few escape sequences, '\A', '\b', '\o', '\w', '\X', and '\Z', accept a newline as a delimiter. Newlines that serve as delimiters continue to be recognized as input line terminators. A caf\o e\(aa in Paris => A café in Paris Use of newlines as delimiters in escape sequences is also discouraged. Finally, the escape sequences '\D', '\h', '\H', '\l', '\L', '\N', '\R', '\s', '\S', '\v', and '\x' prohibit many delimiters. * the numerals '0'-'9' and the decimal point '.' * the (single-character) operators '+-/*%<>=&:()' * the space and tab characters * any escape sequences other than '\%', '\:', '\{', '\}', '\'', '\`', '\-', '\_', '\!', '\/', '\c', '\e', and '\p' Delimiter syntax is complex and flexible primarily for historical reasons; the foregoing restrictions need be kept in mind mainly when using 'groff' in AT&T compatibility mode. GNU 'troff' keeps track of the nesting depth of escape sequence interpolations, so the only characters you need to avoid using as delimiters are those that appear in the arguments you input, not any that result from interpolation. Typically, ''' works fine. *Note Implementation Differences::. $ groff -Tps .de Mw . nr wd \w'\\$1' . tm "\\$1" is \\n(wd units wide. .. .Mw Wet'suwet'en .Mw Wet+200i .cp 1 \" turn on compatibility mode .Mw Wet'suwet'en .Mw Wet' .Mw Wet+200i error-> "Wet'suwet'en" is 54740 units wide. error-> "Wet'+200i" is 42610 units wide. error-> "Wet'suwet'en" is 15860 units wide. error-> "Wet'" is 15860 units wide. error-> "Wet'+200i" is 14415860 units wide. We see here that in compatibility mode, the part of the argument after the ''' delimiter escapes from its context and, if nefariously crafted, influences the computation of the WD register's value in a surprising way.  File: groff.info, Node: Comments, Next: Registers, Prev: Formatter Instructions, Up: GNU troff Reference 5.7 Comments ============ One of the most common forms of escape sequence is the comment.(1) (*note Comments-Footnote-1::) -- Escape sequence: \" Start a comment. Everything up to the next newline is ignored. This may sound simple, but it can be tricky to keep the comments from interfering with the appearance of the output. If the escape sequence is to the right of some text or a request, that portion of the line is ignored, but spaces preceding it are processed normally by GNU 'troff'. This affects only the 'ds' and 'as' requests and their variants. One possibly irritating idiosyncrasy is that tabs should not be used to vertically align comments in the source document. Tab characters are not treated as separators between a request name and its first argument, nor between arguments. A comment on a line by itself is treated as a blank line, because after eliminating the comment, that is all that remains. Test \" comment Test => Test => => Test To avoid this, it is common to combine the empty request with the comment escape sequence as '.\"', causing the input line to be ignored. Another commenting scheme sometimes seen is three consecutive single quotes (''''') at the beginning of a line. This works, but GNU 'troff' emits a warning diagnostic (if enabled) about an undefined macro (namely ''''). -- Escape sequence: \# Start a comment; everything up to and including the next newline is ignored. This 'groff' extension was introduced to avoid the problems described above. Test \# comment Test => Test Test -- Request: .ig [end] Ignore input until, in the current conditional block (if any),(2) (*note Comments-Footnote-2::) the macro END is called at the start of a control line, or the control line '..' is encountered if END is not specified. 'ig' is parsed as if it were a macro definition, but its contents are discarded, not stored.(3) (*note Comments-Footnote-3::) hand\c .de TX fasting .. .ig TX This is part of a large block of input that has been temporarily(?) commented out. We can restore it simply by removing the .ig request and the call of its end macro. .TX => handfasting  File: groff.info, Node: Comments-Footnotes, Up: Comments (1) This claim may be more aspirational than descriptive. (2) *Note Conditional Blocks::. (3) Exception: auto-incrementing registers defined outside the ignored region _will_ be modified if interpolated with '\n±' inside it. *Note Auto-increment::.  File: groff.info, Node: Registers, Next: Manipulating Filling and Adjustment, Prev: Formatter Instructions, Up: GNU troff Reference 5.8 Registers ============= In the 'roff' language, numbers can be stored in "registers". Many built-in registers exist, supplying anything from the date to details of formatting parameters. You can also define your own. *Note Identifiers::, for information on constructing a valid name for a register. * Menu: * Setting Registers:: * Interpolating Registers:: * Auto-increment:: * Assigning Register Formats:: * Built-in Registers::  File: groff.info, Node: Setting Registers, Next: Interpolating Registers, Prev: Registers, Up: Registers 5.8.1 Setting Registers ----------------------- Define registers and update their values with the 'nr' request or the '\R' escape sequence. -- Request: .nr ident value -- Escape sequence: \R'ident value' Set register IDENT to VALUE. If IDENT doesn't exist, GNU 'troff' creates it. In the '\R' escape sequence, the delimiter need not be a neutral apostrophe; see *note Delimiters::. It also does not produce an input token in GNU 'troff'. *Note Gtroff Internals::. .nr a (((17 + (3 * 4))) % 4) \n[a] .\R'a (((17 + (3 * 4))) % 4)' \n[a] => 1 1 (Later, we will discuss additional forms of 'nr' and '\R' that can change a register's value after it is dereferenced but before it is interpolated. *Note Auto-increment::.) The complete transparency of '\R' can cause surprising effects if you use registers like '.k', which get evaluated at the time they are accessed. .ll 1.6i . aaa bbb ccc ddd eee fff ggg hhh\R':k \n[.k]' .tm :k == \n[:k] => :k == 126950 . .br . aaa bbb ccc ddd eee fff ggg hhh\h'0'\R':k \n[.k]' .tm :k == \n[:k] => :k == 15000 If you process this with the PostScript device ('-Tps'), there will be a line break eventually after 'ggg' in both input lines. However, after processing the space after 'ggg', the partially collected line is not overfull yet, so GNU 'troff' continues to collect input until it sees the space (or in this case, the newline) after 'hhh'. At this point, the line is longer than the line length, and the line gets broken. In the first input line, since the '\R' escape sequence leaves no traces, the check for the overfull line hasn't been done yet at the point where '\R' gets handled, and you get a value for the '.k' register that is even greater than the current line length. In the second input line, the insertion of '\h'0'' to cause a zero-width motion forces GNU 'troff' to check the line length, which in turn causes the start of a new output line. Now '.k' returns the expected value. 'nr' and '\R' each have two additional special forms to increment or decrement a register. -- Request: .nr ident +value -- Request: .nr ident -value -- Escape sequence: \R'ident +value' -- Escape sequence: \R'ident -value' Increment (decrement) register IDENT by VALUE. In the '\R' escape sequence, the delimiter need not be a neutral apostrophe; see *note Delimiters::. .nr a 1 .nr a +1 \na => 2 A leading minus sign in VALUE is always interpreted as a decrementation operator, not an algebraic sign. To assign a register a negative value or the negated value of another register, you can force GNU 'troff' to interpret '-' as a negation or minus, rather than decrementation, operator: enclose it with its operand in parentheses or subtract it from zero. .nr a 7 .nr b 3 .nr a -\nb \na => 4 .nr a (-\nb) \na => -3 .nr a 0-\nb \na => -3 If a register's prior value does not exist (the register was undefined), an increment or decrement is applied as if to 0. -- Request: .rr ident Remove register IDENT. If IDENT doesn't exist, the request is ignored. Technically, only the name is removed; the register's contents are still accessible under aliases created with 'aln', if any. -- Request: .rnn ident1 ident2 Rename register IDENT1 to IDENT2. If IDENT1 doesn't exist, the request is ignored. Renaming a built-in register does not otherwise alter its properties. -- Request: .aln new old Create an alias NEW for an existing register OLD, causing the names to refer to the same stored object. If OLD is undefined, a warning in category 'reg' is produced and the request is ignored. *Note Warnings::, for information about the enablement and suppression of warnings. To remove a register alias, invoke 'rr' on its name. A register's contents do not become inaccessible until it has no more names.  File: groff.info, Node: Interpolating Registers, Next: Auto-increment, Prev: Setting Registers, Up: Registers 5.8.2 Interpolating Registers ----------------------------- Register contents are interpolated with the '\n' escape sequence. -- Escape sequence: \ni -- Escape sequence: \n(id -- Escape sequence: \n[ident] Interpolate register with name IDENT (one-character name I, two-character name ID). '\n' is interpreted even in copy mode (*note Copy Mode::). If the register is undefined, it is created and assigned a value of '0', that value is interpolated, and a warning in category 'reg' is emitted. *Note Warnings::, for information about the enablement and suppression of warnings. .nr a 5 .nr as \na+\na \n(as => 10 .nr a1 5 .nr ab 6 .ds str b .ds num 1 \n[a\n[num]] => 5 \n[a\*[str]] => 6  File: groff.info, Node: Auto-increment, Next: Assigning Register Formats, Prev: Interpolating Registers, Up: Registers 5.8.3 Auto-increment -------------------- Registers can also be incremented or decremented by a configured amount at the time they are interpolated. The value of the increment is specified with a third argument to the 'nr' request, and a special interpolation syntax is used to alter and then retrieve the register's value. Together, these features are called "auto-increment".(1) (*note Auto-increment-Footnote-1::) -- Request: .nr ident value incr Set register IDENT to VALUE and its auto-incrementation amount to to INCR. The '\R' escape sequence doesn't support an INCR argument. Auto-incrementation is not _completely_ automatic; the '\n' escape sequence in its basic form never alters the value of a register. To apply auto-incrementation to a register, interpolate it with '\n±'. -- Escape sequence: \n+i -- Escape sequence: \n-i -- Escape sequence: \n+(id -- Escape sequence: \n-(id -- Escape sequence: \n+[ident] -- Escape sequence: \n-[ident] Increment or decrement IDENT (one-character name I, two-character name ID) by the register's auto-incrementation value and then interpolate the new register value. If IDENT has no auto-incrementation value, interpolate as with '\n'. .nr a 0 1 .nr xx 0 5 .nr foo 0 -2 \n+a, \n+a, \n+a, \n+a, \n+a .br \n-(xx, \n-(xx, \n-(xx, \n-(xx, \n-(xx .br \n+[foo], \n+[foo], \n+[foo], \n+[foo], \n+[foo] => 1, 2, 3, 4, 5 => -5, -10, -15, -20, -25 => -2, -4, -6, -8, -10 To change the increment value without changing the value of a register, assign the register's value to itself by interpolating it, and specify the desired increment normally. Apply an increment of '0' to disable auto-incrementation of the register.  File: groff.info, Node: Auto-increment-Footnotes, Up: Auto-increment (1) A negative auto-increment can be considered an "auto-decrement".  File: groff.info, Node: Assigning Register Formats, Next: Built-in Registers, Prev: Auto-increment, Up: Registers 5.8.4 Assigning Register Formats -------------------------------- A writable register's value can be interpolated in several number formats. By default, conventional Arabic numerals are used. Other formats see use in sectioning and outlining schemes and alternative page numbering arrangements. -- Request: .af reg fmt Use number format FMT when interpolating register REG. Valid number formats are as follows. '0...' Arabic numerals 0, 1, 2, and so on. Any decimal digit is equivalent to '0'; the formatter merely counts the digits specified. Multiple Arabic numerals in FMT cause interpolations to be zero-padded on the left if necessary to at least as many digits as specified (interpolations never truncate a register value). A register with format '00' interpolates values 1, 2, 3 as '01', '02', '03'. The default format for all writable registers is '0'. 'I' Uppercase Roman numerals: 0, I, II, III, IV, ... 'i' Lowercase Roman numerals: 0, i, ii, iii, iv, ... 'A' Uppercase letters: 0, A, B, C, ..., Z, AA, AB, ... 'a' Lowercase letters: 0, a, b, c, ..., z, aa, ab, ... Omitting FMT causes a warning in category 'missing'. *Note Warnings::, for information about the enablement and suppression of warnings. Specifying an unrecognized format is an error. Zero values are interpolated as '0' in non-Arabic formats. Negative quantities are prefixed with '-' irrespective of format. In Arabic formats, the sign supplements the field width. If REG doesn't exist, it is created with a zero value. .nr a 10 .af a 0 \" the default format \na, .af a I \na, .af a 321 .nr a (-\na) \na, .af a a \na => 10, X, -010, -j The representable extrema in the 'i' and 'I' formats correspond to Arabic ±39,999. GNU 'troff' uses 'w' and 'z' to represent 5,000 and 10,000 in Roman numerals, respectively, following the convention of AT&T 'troff'--currently, the correct glyphs for Roman numerals five thousand ('U+2181') and ten thousand ('U+2182') are not used. Assigning the format of a read-only register is an error. Instead, copy the read-only register's value to, and assign the format of, a writable register. -- Escape sequence: \gr -- Escape sequence: \g(rg -- Escape sequence: \g[reg] Interpolate the format of the register REG (one-character name R, two-character name RG). Zeroes represent Arabic formats. If REG is not defined, REG is not created and nothing is interpolated. '\g' is interpreted even in copy mode (*note Copy Mode::). GNU 'troff' interprets only Arabic numerals. The Roman numeral or alphabetic formats cannot be used as operands to arithmetic operators in expressions (*note Numeric Expressions::). For instance, it may be desirable to test the page number independently of its format. .af % i \" front matter .de header-trap . \" To test the page number, we need it in Arabic. . ds saved-page-number-format \\g%\" . af % 0 . nr page-number-in-decimal \\n% . af % \\*[saved-page-number-format] . ie \\n[page-number-in-decimal]=1 .do-first-page-stuff . el \{\ . ie o .do-odd-numbered-page-stuff . el .do-even-numbered-page-stuff . \} . rm saved-page-number-format .. .wh 0 header-trap  File: groff.info, Node: Built-in Registers, Prev: Assigning Register Formats, Up: Registers 5.8.5 Built-in Registers ------------------------ Predefined registers whose identifiers start with a dot are read-only. Many are Boolean-valued, interpolating a true or false value testable with the 'if', 'ie', or 'while' requests. Some read-only registers are string-valued, meaning that they interpolate text. *Caution:* Built-in registers are subject to removal like others; once removed, they can be recreated only as normal writable registers and will not reflect formatter state. A register name (without the dot) is often associated with a request of the same name. A complete listing of all built-in registers can be found in *note Register Index::. We present here a few built-in registers that are not described elsewhere in this manual; they have to do with invariant properties of GNU 'troff', or obtain information about the formatter's command-line options, processing progress, or the operating environment. '\n[.A]' Approximate output is being formatted (Boolean-valued); see 'groff' '-a' option (*note Groff Options::). '\n[.c]' '\n[c.]' Input line number. 'c.' is a writable synonym, affecting subsequent interpolations of both '.c' and 'c.'. '\n[.F]' Name of input file (string-valued). '\n[.g]' Always true in GNU 'troff' (Boolean-valued). Documents can use this to ask the formatter if it claims 'groff' compatibility. '\n[.P]' Output page selection status (Boolean-valued); see 'groff' '-o' option (*note Groff Options::). '\n[.R]' Count of available unused registers; always 10,000 in GNU 'troff'.(1) (*note Built-in Registers-Footnote-1::) '\n[.T]' Indicator of output device selection (Boolean-valued); see 'groff' '-T' option (*note Groff Options::). '\n[.U]' Unsafe mode enablement status (Boolean-valued); see 'groff' '-U' option (*note Groff Options::). '\n[.x]' Major version number of the running GNU 'troff' formatter. For example, if the version number is 1.23.0, then '.x' contains '1'. '\n[.y]' Minor version number of the running GNU 'troff' formatter. For example, if the version number is 1.23.0, then '.y' contains '23'. '\n[.Y]' Revision number of the running GNU 'troff' formatter. For example, if the version number is 1.23.0, then '.Y' contains '0'. '\n[$$]' Process identifier (PID) of the GNU 'troff' program in its operating environment. Date- and time-related registers are set per the local time as determined by 'localtime(3)' when the formatter launches. This initialization can be overridden by 'SOURCE_DATE_EPOCH' and 'TZ'; see *note Environment::. '\n[seconds]' Count of seconds elapsed in the minute (0-60). '\n[minutes]' Count of minutes elapsed in the hour (0-59). '\n[hours]' Count of hours elapsed since midnight (0-23). '\n[dw]' Day of the week (1-7; 1 is Sunday). '\n[dy]' Day of the month (1-31). '\n[mo]' Month of the year (1-12). '\n[year]' Gregorian year. '\n[yr]' Gregorian year minus 1900. This register is incorrectly documented in the AT&T 'troff' manual as storing the last two digits of the current year. That claim stopped being true in 2000. Old 'troff' input that looks like: '\" The year number is a surprise after 1999. This document was formatted in 19\n(yr. can be corrected to: This document was formatted in \n[year]. or, for portability across many 'roff' programs, to the following. .nr y4 1900+\n(yr This document was formatted in \n(y4.  File: groff.info, Node: Built-in Registers-Footnotes, Up: Built-in Registers (1) GNU 'troff' dynamically allocates memory for as many registers as required.  File: groff.info, Node: Manipulating Filling and Adjustment, Next: Manipulating Hyphenation, Prev: Registers, Up: GNU troff Reference 5.9 Manipulating Filling and Adjustment ======================================= When an output line is pending (see below), a break moves the drawing position to the beginning of the next text baseline, interrupting filling. Various ways of causing breaks were shown in *note Breaking::. The 'br' request likewise causes a break. Several other requests imply breaks: 'bp', 'ce', 'cf', 'fi', 'fl', 'in', 'nf', 'rj', 'sp', 'ti', and 'trf'. If the no-break control character is used with any of these requests, GNU 'troff' suppresses the break; instead the requested operation takes effect at the next break. ''br' does nothing. .ll 55n This line is normally filled and adjusted. .br A line's alignment is decided 'ce \" Center the next input line (no break). when it is output. This line returns to normal filling and adjustment. => This line is normally filled and adjusted. => A line's alignment is decided when it is output. => This line returns to normal filling and adjustment. Output line properties like page offset, indentation, adjustment, and even the location of its text baseline, are not determined until the line has been broken. An output line is said to be "pending" if some input has been collected but an output line corresponding to it has not yet been written; such an output line is also termed "partially collected". If no output line is pending, it is as if a break has already happened; additional breaks, whether explicit or implicit, have no effect. If the vertical drawing position is negative--as it is when the formatter starts up--a break starts a new page (even if no output line is pending) unless an end-of-input macro is being interpreted. *Note End-of-input Traps::. -- Request: .br Break the line: emit any pending output line without adjustment. foo bar .br baz 'br qux => foo bar => baz qux Sometimes you want to prevent a break within a phrase or between a quantity and its units. -- Escape sequence: \~ Insert an unbreakable space that is adjustable like an ordinary space. It is discarded from the end of an output line if a break is forced. Set the output speed to\~1. There are 1,024\~bytes in 1\~KiB. J.\~F.\~Ossanna wrote the original CSTR\~#54. By default, GNU 'troff' fills text and adjusts it to reach the output line length. The 'nf' request disables filling; the 'fi' request reënables it. -- Request: .fi -- Register: \n[.u] Enable filling of output lines; a pending output line is broken. The read-only register '.u' is set to 1. The filling enablement status, sometimes called "fill mode", is associated with the environment (*note Environments::). *Note Line Continuation::, for interaction with the '\c' escape sequence. -- Request: .nf Disable filling of output lines: the output line length (*note Line Layout::) is ignored and output lines are broken where the input lines are. A pending output line is broken and adjustment is suppressed. The read-only register '.u' is set to 0. The filling enablement status is associated with the environment (*note Environments::). See *note Line Continuation::, for interaction with the '\c' escape sequence. -- Request: .ad [mode] -- Register: \n[.j] Enable output line adjustment in MODE, taking effect when the pending (or next) output line is broken. Adjustment is suppressed when filling is. MODE can have one of the following values. 'b' 'n' Adjust "normally": if the output line does not consume the distance between the indentation and the configured output line length, GNU 'troff' stretches adjustable spaces within the line until that length is reached. When the indentation is zero, this mode spreads the line to both the left and right margins. This is the GNU 'troff' default. 'c' Center filled text. Contrast with the 'ce' request, which centers text _without_ filling it. 'l' Align text to the left without adjusting it. 'r' Align text to the right without adjusting it. MODE can also be a value previously stored in the '.j' register. Using 'ad' without an argument is the same as '.ad \n[.j]'; unless filling is disabled, GNU 'troff' resumes adjusting lines in the same way it did before adjustment was disabled by invocation of the 'na' request. The adjustment mode and enablement status are encoded in the read-only register '.j'. These parameters are associated with the environment (*note Environments::). The value of '.j' for any adjustment mode is an implementation detail and should not be relied upon as a programmer's interface. Do not write logic to interpret or perform arithmetic on it. .ll 48n .de AD . br . ad \\$1 .. .de NA . br . na .. left .AD r .nr ad \n(.j right .AD c center .NA left .AD center .AD \n(ad right => left => right => center => left => center => right -- Request: .na Disable output line adjustment. This produces the same output as left-alignment, but the value of the adjustment mode register '.j' is altered differently. The adjustment mode and enablement status are associated with the environment (*note Environments::). -- Request: .brp -- Escape sequence: \p Break, adjusting the line per the current adjustment mode. '\p' schedules a break with adjustment at the next word boundary. The escape sequence is itself neither a break nor a space of any kind; it can thus be placed in the middle of a word to cause a break at the end of that word. Breaking with immediate adjustment can produce ugly results since GNU 'troff' doesn't have a sophisticated paragraph-building algorithm, as TeX has, for example. Instead, GNU 'troff' fills and adjusts a paragraph line by line. .ll 4.5i This is an uninteresting sentence. This is an uninteresting sentence.\p This is an uninteresting sentence. is formatted as follows. This is an uninteresting sentence. This is an uninteresting sentence. This is an uninteresting sentence. To clearly present the next couple of requests, we must introduce the concept of "productive" input lines. A "productive input line" is one that directly produces formatted output. Text lines produce output,(1) (*note Manipulating Filling and Adjustment-Footnote-1::) as do control lines containing requests like 'tl' or escape sequences like '\D'. Macro calls are not _directly_ productive, and thus not counted, but their interpolated contents can be. Empty requests, and requests and escape sequences that define registers or strings or alter the formatting environment (as with changes to the size, face, height, slant, or color of the type) are not productive. We will also preview the output line continuation escape sequence, '\c', which "connects" two input lines that would otherwise be counted separately. (2) (*note Manipulating Filling and Adjustment-Footnote-2::) .de hello Hello, world! .. .ce \" center output of next productive input line . .nr junk-reg 1 .ft I Chorus: \c .ft .hello Went the day well? => Chorus: Hello, world! => Went the day well? -- Request: .ce [n] -- Register: \n[.ce] Break (unless the no-break control character is used), center the output of the next N productive input lines with respect to the line length and indentation without filling, then break again regardless of the invoking control character. If the argument is not positive, centering is disabled. Omitting the argument implies an N of '1'. The count of lines remaining to be centered is stored in the read-only register '.ce' and is associated with the environment (*note Environments::). While the '.ad c' request also centers text, it fills the text as well. .de FR This is a small text fragment that shows the differences between the `.ce' and the `.ad c' requests. .. .ll 4i .ce 1000 .FR .ce 0 .ad c .FR => This is a small text fragment that shows => the differences => between the `.ce' and the `.ad c' requests. => => This is a small text fragment that shows => the differences between the `.ce' and => the `.ad c' requests. The previous example illustrates a common idiom of turning centering on for a quantity of lines far in excess of what is required, and off again after the text to be centered. This technique relieves humans of counting lines for requests that take a count of input lines as an argument. -- Request: .rj [n] -- Register: \n[.rj] Break (unless the no-break control character is used), align the output of the next N productive input lines to the right margin without filling, then break again regardless of the control character. If the argument is not positive, right-alignment is disabled. Omitting the argument implies an N of '1'. The count of lines remaining to be right-aligned is stored in the read-only register '.rj' and is associated with the environment (*note Environments::). .ll 49n .rj 3 At first I hoped that such a technically unsound project would collapse but I soon realized it was doomed to success. \[em] C. A. R. Hoare => At first I hoped that such a technically unsound => project would collapse but I soon realized it was => doomed to success. -- C. A. R. Hoare -- Request: .ss word-space-size [additional-sentence-space-size] -- Register: \n[.ss] -- Register: \n[.sss] Set the sizes of spaces between words and sentences(3) (*note Manipulating Filling and Adjustment-Footnote-3::) in twelfths of font's space width (typically one-fourth to one-third em for Western scripts). The default for both parameters is 12. Negative values are erroneous. The first argument is a minimum; if an output line undergoes adjustment, such spaces may increase in width. The optional second argument sets the amount of additional space separating sentences on the same output line. If omitted, this amount is set to WORD-SPACE-SIZE. The request is ignored if there are no parameters. Additional inter-sentence space is used only if the output line is not full when the end of a sentence occurs in the input. If a sentence ends at the end of an input line, then both an inter-word space and an inter-sentence space are added to the output; if two spaces follow the end of a sentence in the middle of an input line, then the second space becomes an inter-sentence space in the output. Additional inter-sentence space is not adjusted, but the inter-word space that always precedes it may be. Further input spaces after the second, if present, are adjusted as normal. The read-only registers '.ss' and '.sss' hold the minimal inter-word space and additional inter-sentence space amounts, respectively. These parameters are part of the environment (*note Environments::), and rounded down to the nearest multiple of 12 on terminals. The 'ss' request can insert discardable horizontal space; that is, space that is discarded at a break. For example, some footnote styles collect the notes into a single paragraph with large gaps between each note. .ll 48n 1.\~J. Fict. Ch. Soc. 6 (2020), 3\[en]14. .ss 12 48 \" applies to next sentence ending Reprints no longer available through FCS. .ss 12 \" go back to normal 2.\~Better known for other work. => 1. J. Fict. Ch. Soc. 6 (2020), 3-14. Reprints => no longer available through FCS. 2. Better => known for other work. If _undiscardable_ space is required, use the '\h' escape sequence.  File: groff.info, Node: Manipulating Filling and Adjustment-Footnotes, Up: Manipulating Filling and Adjustment (1) unless diverted; see *note Diversions:: (2) *Note Line Continuation::. (3) Recall *note Filling:: and *note Sentences:: for the definitions of word and sentence boundaries, respectively.  File: groff.info, Node: Manipulating Hyphenation, Next: Manipulating Spacing, Prev: Manipulating Filling and Adjustment, Up: GNU troff Reference 5.10 Manipulating Hyphenation ============================= When filling, GNU 'troff' hyphenates words as needed at user-specified and automatically determined hyphenation points. The machine-driven determination of hyphenation points in words requires algorithms and data, and is susceptible to conventions and preferences. Before tackling such "automatic hyphenation", let us consider how hyphenation points can be set explicitly. Explicitly hyphenated words such as "mother-in-law" are eligible for breaking after each of their hyphens. Relatively few words in a language offer such obvious break points, however, and automatic detection of syllabic (or phonetic) boundaries for hyphenation is not perfect,(1) (*note Manipulating Hyphenation-Footnote-1::) particularly for unusual words found in technical literature. We can instruct GNU 'troff' how to hyphenate specific words if the need arises. -- Request: .hw word ... Define each "hyphenation exception" WORD with each hyphen '-' in the word indicating a hyphenation point. For example, the request .hw in-sa-lub-rious alpha marks potential hyphenation points in "insalubrious", and prevents "alpha" from being hyphenated at all. Besides the space character, any character whose hyphenation code is zero can be used to separate the arguments of 'hw' (see the 'hcode' request below). In addition, this request can be used more than once. Hyphenation points specified with 'hw' are not subject to the within-word placement restrictions imposed by the 'hy' request (see below). Hyphenation exceptions specified with the 'hw' request are associated with the hyphenation language (see the 'hla' request below) and environment (*note Environments::); invoking the 'hw' request in the absence of a hyphenation language is an error. The request is ignored if there are no parameters. These are known as hyphenation exceptions in the expectation that most users will avail themselves of automatic hyphenation; these exceptions override any rules that would normally apply to a word matching a hyphenation exception defined with 'hw'. Situations also arise when only a specific occurrence of a word needs its hyphenation altered or suppressed, or when a URL or similar string needs to be breakable in sensible places without hyphenation. -- Escape sequence: \% -- Escape sequence: \: To tell GNU 'troff' how to hyphenate words as they occur in input, use the '\%' escape sequence; it is the default "hyphenation character". Each instance within a word indicates to GNU 'troff' that the word may be hyphenated at that point, while prefixing a word with this escape sequence prevents it from being otherwise hyphenated. This mechanism affects only that occurrence of the word; to change the hyphenation of a word for the remainder of input processing, use the 'hw' request. GNU 'troff' regards the escape sequences '\X' and '\Y' as starting a word; that is, the '\%' escape sequence in, say, '\X'...'\%foobar' or '\Y'...'\%foobar' no longer prevents hyphenation of 'foobar' but inserts a hyphenation point just prior to it; most likely this isn't what you want. *Note Postprocessor Access::. '\:' inserts a non-printing break point; that is, a word can break there, but the soft hyphen glyph (see below) is not written to the output if it does. This escape sequence is an input word boundary, so the remainder of the word is subject to hyphenation as normal. You can combine '\:' and '\%' to control breaking of a file name or URL, or to permit hyphenation only after certain explicit hyphens within a word. The \%Lethbridge-Stewart-\:\%Sackville-Baggins divorce was, in retrospect, inevitable once the contents of \%/var/log/\:\%httpd/\:\%access_log on the family web server came to light, revealing visitors from Hogwarts. -- Request: .hc [char] Change the hyphenation character to CHAR. This character then works as the '\%' escape sequence normally does, and thus no longer appears in the output.(2) (*note Manipulating Hyphenation-Footnote-2::) Without an argument, 'hc' resets the hyphenation character to '\%' (the default). The hyphenation character is associated with the environment (*note Environments::). -- Request: .shc [c] Set the "soft hyphen character", inserted when a word is hyphenated automatically or at a hyphenation character, to the ordinary or special character C.(3) (*note Manipulating Hyphenation-Footnote-3::) If the argument is omitted, the soft hyphen character is set to the default, '\[hy]'. If no glyph for C exists in the font in use at a potential hyphenation point, then the line is not broken there. Neither character definitions (specified with the 'char' and similar requests) nor translations (specified with the 'tr' request) are applied to C. Several requests influence automatic hyphenation. Because conventions vary, a variety of hyphenation modes is available to the 'hy' request; these determine whether hyphenation will apply to a word prior to breaking a line at the end of a page (more or less; see below for details), and at which positions within that word automatically determined hyphenation points are permissible. The places within a word that are eligible for hyphenation are determined by language-specific data and lettercase relationships. Furthermore, hyphenation of a word might be suppressed due to a limit on consecutive hyphenated lines ('hlm'), a minimum line length threshold ('hym'), or because the line can instead be adjusted with additional inter-word space ('hys'). -- Request: .hy [mode] -- Register: \n[.hy] Set automatic hyphenation mode to MODE, an integer encoding conditions for hyphenation; if omitted, '1' is implied. The hyphenation mode is available in the read-only register '.hy'; it is associated with the environment (*note Environments::). The default hyphenation mode depends on the localization file loaded when GNU 'troff' starts up; see the 'hpf' request below. Typesetting practice generally does not avail itself of every opportunity for hyphenation, but the details differ by language and site mandates. The hyphenation modes of AT&T 'troff' were implemented with English-language publishing practices of the 1970s in mind, not a scrupulous enumeration of conceivable parameters. GNU 'troff' extends those modes such that finer-grained control is possible, favoring compatibility with older implementations over a more intuitive arrangement. The means of hyphenation mode control is a set of numbers that can be added up to encode the behavior sought.(4) (*note Manipulating Hyphenation-Footnote-4::) The entries in the following table are termed "values"; the sum of the desired values is the "mode". '0' disables hyphenation. '1' enables hyphenation except after the first and before the last character of a word. The remaining values "imply" 1; that is, they enable hyphenation under the same conditions as '.hy 1', and then apply or lift restrictions relative to that basis. '2' disables hyphenation of the last word on a page,(5) (*note Manipulating Hyphenation-Footnote-5::) even for explicitly hyphenated words. '4' disables hyphenation before the last two characters of a word. '8' disables hyphenation after the first two characters of a word. '16' enables hyphenation before the last character of a word. '32' enables hyphenation after the first character of a word. Apart from value 2, restrictions imposed by the hyphenation mode are _not_ respected for words whose hyphenations have been specified with the hyphenation character ('\%' by default) or the 'hw' request. Nonzero values in the previous table are additive. For example, mode 12 causes GNU 'troff' to hyphenate neither the last two nor the first two characters of a word. Some values cannot be used together because they contradict; for instance, values 4 and 16, and values 8 and 32. As noted, it is superfluous to add 1 to any non-zero even mode. The automatic placement of hyphens in words is determined by "pattern files", which are derived from TeX and available for several languages. The number of characters at the beginning of a word after which the first hyphenation point should be inserted is determined by the patterns themselves; it can't be reduced further without introducing additional, invalid hyphenation points (unfortunately, this information is not part of a pattern file--you have to know it in advance). The same is true for the number of characters at the end of a word before the last hyphenation point should be inserted. For example, you can supply the following input to 'echo $(nroff)'. .ll 1 .hy 48 splitting You will get s- plit- t- in- g instead of the correct 'split- ting'. English patterns as distributed with GNU 'troff' need two characters at the beginning and three characters at the end; this means that value 4 of 'hy' is mandatory. Value 8 is possible as an additional restriction, but values 16 and 32 should be avoided, as should mode 1. Modes 4 and 6 are typical. A table of left and right minimum character counts for hyphenation as needed by the patterns distributed with GNU 'troff' follows; see the 'groff_tmac(5)' man page for more information on GNU 'troff''s language macro files. language pattern name left min right min ----------------------------------------------------------- Czech cs 2 2 English en 2 3 French fr 2 3 German traditional det 2 2 German reformed den 2 2 Italian it 2 2 Swedish sv 1 2 Hyphenation exceptions within pattern files (i.e., the words within a TeX '\hyphenation' group) obey the hyphenation restrictions given by 'hy'. -- Request: .nh Disable automatic hyphenation; i.e., set the hyphenation mode to 0 (see above). The hyphenation mode of the last call to 'hy' is not remembered. -- Request: .hpf pattern-file -- Request: .hpfa pattern-file -- Request: .hpfcode a b [c d] ... Read hyphenation patterns from PATTERN-FILE, which is sought in the same way that macro files are with the 'mso' request or the '-mNAME' command-line option to 'groff'. The PATTERN-FILE should have the same format as (simple) TeX pattern files. More specifically, the following scanning rules are implemented. * A percent sign starts a comment (up to the end of the line) even if preceded by a backslash. * "Digraphs" like '\$' are not supported. * '^^XX' (where each X is 0-9 or a-f) and '^^C' (character C in the code point range 0-127 decimal) are recognized; other uses of '^' cause an error. * No macro expansion is performed. * 'hpf' checks for the expression '\patterns{...}' (possibly with whitespace before or after the braces). Everything between the braces is taken as hyphenation patterns. Consequently, '{' and '}' are not allowed in patterns. * Similarly, '\hyphenation{...}' gives a list of hyphenation exceptions. * '\endinput' is recognized also. * For backward compatibility, if '\patterns' is missing, the whole file is treated as a list of hyphenation patterns (except that the '%' character is recognized as the start of a comment). The 'hpfa' request appends a file of patterns to the current list. The 'hpfcode' request defines mapping values for character codes in pattern files. It is an older mechanism no longer used by GNU 'troff''s own macro files; for its successor, see 'hcode' below. 'hpf' or 'hpfa' apply the mapping after reading the patterns but before replacing or appending to the active list of patterns. Its arguments are pairs of character codes--integers from 0 to 255. The request maps character code A to code B, code C to code D, and so on. Character codes that would otherwise be invalid in GNU 'troff' can be used. By default, every code maps to itself except those for letters 'A' to 'Z', which map to those for 'a' to 'z'. The set of hyphenation patterns is associated with the language set by the 'hla' request (see below). The 'hpf' request is usually invoked by a localization file loaded by the 'troffrc' file.(6) (*note Manipulating Hyphenation-Footnote-6::) A second call to 'hpf' (for the same language) replaces the hyphenation patterns with the new ones. Invoking 'hpf' or 'hpfa' causes an error if there is no hyphenation language. If no 'hpf' request is specified (either in the document, in a file loaded at startup, or in a macro package), GNU 'troff' won't automatically hyphenate at all. -- Request: .hcode c1 code1 [c2 code2] ... Set the hyphenation code of character C1 to CODE1, that of C2 to CODE2, and so on. A hyphenation code must be an ordinary character (not a special character escape sequence) other than a digit or a space. The request is ignored if given no arguments. For hyphenation to work, hyphenation codes must be set up. At startup, GNU 'troff' assigns hyphenation codes to the letters 'a'-'z' (mapped to themselves), to the letters 'A'-'Z' (mapped to 'a'-'z'), and zero to all other characters. Normally, hyphenation patterns contain only lowercase letters which should be applied regardless of case. In other words, they assume that the words 'FOO' and 'Foo' should be hyphenated exactly as 'foo' is. The 'hcode' request extends this principle to letters outside the Unicode basic Latin alphabet; without it, words containing such letters won't be hyphenated properly even if the corresponding hyphenation patterns contain them. For example, the following 'hcode' requests are necessary to assign hyphenation codes to the letters 'ÄäÖöÜüß', needed for German. .hcode ä ä Ä ä .hcode ö ö Ö ö .hcode ü ü Ü ü .hcode ß ß Without these assignments, GNU 'troff' treats the German word 'Kindergärten' (the plural form of 'kindergarten') as two words 'kinderg' and 'rten' because the hyphenation code of the umlaut a is zero by default, just like a space. There is a German hyphenation pattern that covers 'kinder', so GNU 'troff' finds the hyphenation 'kin-der'. The other two hyphenation points ('kin-der-gär-ten') are missed. -- Request: .hla lang -- Register: \n[.hla] Set the hyphenation language to LANG. Hyphenation exceptions specified with the 'hw' request and hyphenation patterns and exceptions specified with the 'hpf' and 'hpfa' requests are associated with the hyphenation language. The 'hla' request is usually invoked by a localization file, which is turn loaded by the 'troffrc' or 'troffrc-end' file; see the 'hpf' request above. The hyphenation language is available in the read-only string-valued register '.hla'; it is associated with the environment (*note Environments::). -- Request: .hlm [n] -- Register: \n[.hlm] -- Register: \n[.hlc] Set the maximum quantity of consecutive hyphenated lines to N. If N is negative, there is no maximum. If omitted, N is -1. This value is associated with the environment (*note Environments::). Only lines output from a given environment count toward the maximum associated with that environment. Hyphens resulting from '\%' are counted; explicit hyphens are not. The '.hlm' read-only register stores this maximum. The count of immediately preceding consecutive hyphenated lines is available in the read-only register '.hlc'. -- Request: .hym [length] -- Register: \n[.hym] Set the (right) hyphenation margin to LENGTH. If the adjustment mode is not 'b' or 'n', the line is not hyphenated if it is shorter than LENGTH. Without an argument, the hyphenation margin is reset to its default value, 0. The default scaling unit is 'm'. The hyphenation margin is associated with the environment (*note Environments::). A negative argument resets the hyphenation margin to zero, emitting a warning in category 'range'. The hyphenation margin is available in the '.hym' read-only register. -- Request: .hys [hyphenation-space] -- Register: \n[.hys] Suppress hyphenation of the line in adjustment modes 'b' or 'n' if it can be justified by adding no more than HYPHENATION-SPACE extra space to each inter-word space. Without an argument, the hyphenation space adjustment threshold is set to its default value, 0. The default scaling unit is 'm'. The hyphenation space adjustment threshold is associated with the environment (*note Environments::). A negative argument resets the hyphenation space adjustment threshold to zero, emitting a warning in category 'range'. The hyphenation space adjustment threshold is available in the '.hys' read-only register.  File: groff.info, Node: Manipulating Hyphenation-Footnotes, Up: Manipulating Hyphenation (1) Whether a perfect algorithm for this application is even possible is an unsolved problem in computer science: . (2) '\%' itself stops marking hyphenation points but still produces no output glyph. (3) "Soft" because it appears in output only where a hyphenation break is performed; a "hard" hyphen, as in "long-term", always appears. (4) The mode is a vector of Booleans encoded as an integer. To a programmer, this fact is easily deduced from the exclusive use of powers of two for the configuration parameters; they are computationally easy to "mask off" and compare to zero. To almost everyone else, the arrangement seems recondite and unfriendly. (5) Hyphenation is prevented if the next page location trap is closer to the vertical drawing position than the next text baseline would be. *Note Page Location Traps::. (6) For more on localization, see the 'groff_tmac(5)' man page.  File: groff.info, Node: Manipulating Spacing, Next: Tabs and Fields, Prev: Manipulating Hyphenation, Up: GNU troff Reference 5.11 Manipulating Spacing ========================= A break causes the formatter to update the vertical drawing position at which the new text baseline is aligned. You can alter this location. -- Request: .sp [distance] Break and move the next text baseline down by DISTANCE, or until springing a page location trap.(1) (*note Manipulating Spacing-Footnote-1::) If invoked with the no-break control character, 'sp' moves the pending output line's text baseline by DISTANCE. A negative DISTANCE will not reduce the position of the text baseline below zero. Inside a diversion, any DISTANCE argument is ignored. The default scaling unit is 'v'. If DISTANCE is not specified, '1v' is assumed. .pl 5v \" Set page length to 5 vees. .de xx \-\-\- . br .. .wh 0 xx \" Set a trap at the top of the page. foo on page \n% .sp 2v bar on page \n% .sp 50v \" This will cause a page break. baz on page \n% .pl \n(nlu \" Truncate page to current position. => --- => foo on page 1 => => => bar on page 1 => --- => baz on page 2 You might use the following macros to set the baseline of the next output text at a given distance from the top or the bottom of the page. We subtract one line height ('\n[.v]') because the '|' operator moves to one vee below the page top (recall *note Numeric Expressions::). .de y-from-top-down . sp |\\$1-\\n[.v]u .. . .de y-from-bot-up . sp |\\n[.p]u-\\$1-\\n[.v]u .. A call to '.y-from-bot-up 10c' means that the next text baseline will be 10 cm from the bottom edge of the paper. -- Request: .ls [count] -- Register: \n[.L] Set the line spacing; add COUNT-1 blank lines after each line of text. With no argument, GNU 'troff' uses the previous value before the last 'ls' call. The default is '1'. The read-only register '.L' contains the current line spacing; it is associated with the environment (*note Environments::). The 'ls' request is a coarse mechanism. *Note Changing the Type Size::, for the requests 'vs' and 'pvs' as alternatives to 'ls'. -- Escape sequence: \x'spacing' -- Register: \n[.a] Sometimes, an output line requires additional vertical spacing, for instance to allow room for a tall construct like an inline equation with exponents or subscripts (particularly if they are iterated). The '\x' escape sequence takes a delimited measurement (like '\x'3p'') to increase the vertical spacing of the pending output line. The default scaling unit is 'v'. If the measurement is positive, extra vertical space is inserted below the current line; a negative measurement adds space above. If '\x' is applied to the pending output line multiple times, the maxima of the positive and negative adjustments are separately applied. The delimiter need not be a neutral apostrophe; see *note Delimiters::. The '.a' read-only register contains the extra vertical spacing _after_ the text baseline of the most recently emitted output line. (In other words, it is the largest positive argument to '\x' encountered on that line.) This quantity is exposed via a register because if an output line requires this "extra post-vertical line spacing", and the subsequent output line requires "extra pre-vertical line spacing" (a negative argument to '\x'), then applying both can lead to excessive spacing between the output lines. Text that is piling high on line N might not require (as much) extra pre-vertical line spacing if line N-1 carries extra post-vertical line spacing. Use of '\x' can be necessary in combination with the bracket-building escape sequence '\b',(2) (*note Manipulating Spacing-Footnote-2::) as the following example shows. .nf This is a test of \[rs]b (1). This is a test of \[rs]b (2). This is a test of \b'xyz'\x'-1m'\x'1m' (3). This is a test of \[rs]b (4). This is a test of \[rs]b (5). => This is a test of \b (1). => This is a test of \b (2). => x => This is a test of y (3). => z => This is a test of \b (4). => This is a test of \b (5). Without '\x', the backslashes on the lines marked '(2)' and '(4)' would be overprinted. -- Request: .ns -- Request: .rs -- Register: \n[.ns] Enable "no-space mode". Vertical spacing, whether by 'sp' requests or blank input lines, is disabled. The 'bp' request to advance to the next page is also disabled, unless it is accompanied by a page number (*note Page Control::). No-space mode ends automatically when text(3) (*note Manipulating Spacing-Footnote-3::) is formatted for output (4) (*note Manipulating Spacing-Footnote-4::) or the 'rs' request is invoked, which ends no-space mode. The read-only register '.ns' interpolates a Boolean value indicating the enablement of no-space mode. A paragraphing macro might ordinarily insert vertical space to separate paragraphs. A section heading macro could invoke 'ns' to suppress this spacing for the first paragraph in a section.  File: groff.info, Node: Manipulating Spacing-Footnotes, Up: Manipulating Spacing (1) *Note Page Location Traps::. (2) *Note Drawing Geometric Objects::. (3) or geometric objects; see *note Drawing Geometric Objects:: (4) to the top-level diversion; see *note Diversions::  File: groff.info, Node: Tabs and Fields, Next: Character Translations, Prev: Manipulating Spacing, Up: GNU troff Reference 5.12 Tabs and Fields ==================== A tab character (ISO code point 9, EBCDIC code point 5) causes a horizontal movement to the next tab stop, if any. -- Escape sequence: \t Interpolate a tab in copy mode; see *note Copy Mode::. -- Request: .ta [[n1 n2 ... nn ]T r1 r2 ... rn] -- Register: \n[.tabs] Change tab stop positions. This request takes a series of tab specifiers as arguments (optionally divided into two groups with the letter 'T') that indicate where each tab stop is to be, overriding any previous settings. The default scaling unit is 'm'. Invoking 'ta' without an argument removes all tab stops. GNU 'troff''s startup value is 'T 0.5i'. Tab stops can be specified absolutely--as distances from the left margin. The following example sets six tab stops, one every inch. .ta 1i 2i 3i 4i 5i 6i Tab stops can also be specified using a leading '+', which means that the specified tab stop is set relative to the previous tab stop. For example, the following is equivalent to the previous example. .ta 1i +1i +1i +1i +1i +1i GNU 'troff' supports an extended syntax to specify repeating tab stops. These stops appear after a 'T' argument. Their values are always taken as distances relative to the previous tab stop. This is the idiomatic way to specify tab stops at equal intervals in 'groff'. The following is, yet again, the same as the previous examples. It does more, in fact, since it defines an infinite number of tab stops at one-inch intervals. .ta T 1i Now we are ready to interpret the full syntax given above. The 'ta' request sets tabs at positions N1, N2, ..., NN, then at NN+R1, NN+R2, ..., NN+RN, then at NN+RN+R1, NN+RN+R2, ..., NN+RN+RN, and so on. For example, '4c +6c T 3c 5c 2c' is equivalent to '4c 10c 13c 18c 20c 23c 28c 30c ...'. Text written to a tab column (i.e., between two tab stops, or between a tab stop and an output line boundary) may be aligned to the right or left, or centered in the column. This alignment is determined by appending 'R', 'L', or 'C' to the tab specifier. The default is 'L'. .ta 1i 2iC 3iR The beginning of an output line is not a tab stop; the text that begins an output line is placed according to the configured alignment and indentation; see *note Manipulating Filling and Adjustment:: and *note Line Layout::. A tab stop is converted into a non-breakable horizontal movement that cannot be adjusted. .ll 2i .ds foo a\tb\tc .ta T 1i \*[foo] error-> warning: cannot break line => a b c The above creates a single output line that is a bit longer than two inches (we use a string to show exactly where the tab stops are). Now consider the following. .ll 2i .ds bar a\tb c\td .ta T 1i \*[bar] error-> warning: cannot adjust line => a b => c d GNU 'troff' first converts the line's tab stops into unbreakable horizontal movements, then breaks after 'b'. This usually isn't what you want. Superfluous tab characters--those that do not correspond to a tab stop--are ignored except for the first, which delimits the characters belonging to the last tab stop for right-alignment or centering. .ds Z foo\tbar\tbaz .ds ZZ foo\tbar\tbazqux .ds ZZZ foo\tbar\tbaz\tqux .ta 2i 4iR \*[Z] .br \*[ZZ] .br \*[ZZZ] .br => foo bar baz => foo bar bazqux => foo bar bazqux The first line right-aligns "baz" within the second tab stop. The second line right-aligns "bazqux" within it. The third line right-aligns only "baz" because of the additional tab character, which marks the end of the text occupying the last tab stop defined. Tab stops are associated with the environment (*note Environments::). The read-only register '.tabs' contains a string representation of the current tab settings suitable for use as an argument to the 'ta' request.(1) (*note Tabs and Fields-Footnote-1::) .ds tab-string \n[.tabs] \*[tab-string] => T120u -- Request: .tc [c] Set the tab repetition character to the ordinary or special character C; normally, no glyph is written when moving to a tab stop (and some output devices may output space characters to achieve this motion). A "tab repetition character" causes the formatter to write as many instances of C as are necessary to occupy the interval from the horizontal drawing position to the next tab stop. With no argument, GNU 'troff' reverts to the default behavior. The tab repetition character is associated with the environment (*note Environments::). Only a single character of C is recognized; any excess is ignored. -- Request: .linetabs n -- Register: \n[.linetabs] If N is missing or non-zero, activate "line-tabs"; deactivate it otherwise (the default). Active line-tabs cause GNU 'troff' to compute tab distances relative to the start of the output line instead of the input line. .de Tabs . ds x a\t\c . ds y b\t\c . ds z c . ta 1i 3i \\*x \\*y \\*z .. .Tabs .br .linetabs .Tabs => a b c => a b c Line-tabs activation is associated with the environment (*note Environments::). The read-only register '.linetabs' interpolates 1 if line-tabs are active, and 0 otherwise. * Menu: * Leaders:: * Fields::  File: groff.info, Node: Tabs and Fields-Footnotes, Up: Tabs and Fields (1) Plan 9 'troff' uses the register '.S' for this purpose.  File: groff.info, Node: Leaders, Next: Fields, Prev: Tabs and Fields, Up: Tabs and Fields 5.12.1 Leaders -------------- Sometimes it is desirable to fill a tab stop with a given glyph, but also use tab stops normally on the same output line. An example is a table of contents entry that uses dots to bridge the entry name with its page number, which is itself aligned between tab stops. The 'roff' language provides "leaders" for this purpose.(1) (*note Leaders-Footnote-1::) A leader character (ISO and EBCDIC code point 1, also known as SOH or "start of heading"), behaves similarly to a tab character: it moves to the next tab stop. The difference is that for this movement, the default fill character is a period '.'. -- Escape sequence: \a Interpolate a leader in copy mode; see *note Copy Mode::. -- Request: .lc [c] Set the leader repetition character to the ordinary or special character C. Recall *note Tabs and Leaders::: when encountering a leader character in the input, the formatter writes as many dots '.' as are necessary until reaching the next tab stop; this is the "leader definition character". Omitting C unsets the leader character. With no argument, GNU 'troff' treats leaders the same as tabs. The leader repetition character is associated with the environment (*note Environments::). Only a single C is recognized; any excess is ignored. A table of contents, for example, may define tab stops after a section number, a title, and a gap to be filled with leader dots. The page number follows the leader, after a right-aligned final tab stop wide enough to house the largest page number occurring in the document. .ds entry1 19.\tThe Prophet\a\t98 .ds entry2 20.\tAll Astir\a\t101 .ta .5i 4.5i +.5iR .nf \*[entry1] \*[entry2] => 19. The Prophet............................. 98 => 20. All Astir............................... 101  File: groff.info, Node: Leaders-Footnotes, Up: Leaders (1) This is pronounced to rhyme with "feeder", and refers to how the glyphs "lead" the eye across the page to the corresponding page number or other datum.  File: groff.info, Node: Fields, Prev: Leaders, Up: Tabs and Fields 5.12.2 Fields ------------- "Fields" are a more general way of laying out tabular data. A field is defined as the data between a pair of "delimiting characters". It contains substrings that are separated by "padding characters". The width of a field is the distance on the _input_ line from the position where the field starts to the next tab stop. A padding character inserts an adjustable space similar to TeX's '\hss' command (thus it can even be negative) to make the sum of all substring lengths plus the adjustable space equal to the field width. If more than one padding character is inserted, the available space is evenly distributed among them. -- Request: .fc [delim-char [padding-char]] Define a delimiting and a padding character for fields. If the latter is missing, the padding character defaults to a space character. If there is no argument at all, the field mechanism is disabled (which is the default). In contrast to, e.g., the tab repetition character, delimiting and padding characters are _not_ associated with the environment (*note Environments::). .fc # ^ .ta T 3i #foo^bar^smurf# .br #foo^^bar^smurf# => foo bar smurf => foo bar smurf  File: groff.info, Node: Character Translations, Next: troff and nroff Modes, Prev: Tabs and Fields, Up: GNU troff Reference 5.13 Character Translations =========================== A "translation" is a mapping of an input character to an output glyph. The mapping occurs at output time, i.e., the input character gets assigned the metric information of the mapped output character right before input tokens are converted to nodes (*note Gtroff Internals::, for more on this process). -- Request: .tr abcd... -- Request: .trin abcd... Translate character A to glyph B, character C to glyph D, and so on. If there is an odd number of characters in the argument, the last one is translated to a fixed-width space (the same one obtained by the '\' escape sequence). The 'trin' request is identical to 'tr', but when you unformat a diversion with 'asciify' it ignores the translation. *Note Diversions::, for details about the 'asciify' request. Some notes: * Special characters ('\(XX', '\[XXX]', '\C'XXX'', '\'', '\`', '\-', '\_'), glyphs defined with the 'char' request, and numbered glyphs ('\N'XXX'') can be translated also. * The '\e' escape can be translated also. * Characters can be mapped onto the '\%' and '\~' escape sequences (but '\%' and '\~' can't be mapped onto another glyph). * The following characters can't be translated: space (with one exception, see below), backspace, newline, leader (and '\a'), tab (and '\t'). * Translations are not considered for finding the soft hyphen character set with the 'shc' request. * The pair 'C\&' (an arbitrary character C followed by the dummy character) maps this character to "nothing". .tr a\& foo bar => foo br Even the space character can be mapped to the dummy character. .tr aa \& foo bar => foobar As shown in the example, the space character can't be the first character/glyph pair as an argument of 'tr'. Additionally, it is not possible to map the space character to any other glyph; requests like '.tr aa x' undo '.tr aa \&' instead. If justification is active, lines are justified in spite of the 'empty' space character (but there is no minimal distance, i.e., the space character, between words). * After an output glyph has been constructed (this happens at the moment immediately before the glyph is appended to an output glyph list, either by direct output, in a macro, diversion, or string), it is no longer affected by 'tr'. * Translating character to glyphs where one of them or both are undefined is possible also; 'tr' does not check whether the elements of its argument exist. *Note Gtroff Internals::. * Without an argument, the 'tr' request is ignored. -- Request: .trnt abcd... 'trnt' is the same as the 'tr' request except that the translations do not apply to text that is transparently throughput into a diversion with '\!'. *Note Diversions::. For example, .tr ab .di x \!.tm a .di .x prints 'b' to the standard error stream; if 'trnt' is used instead of 'tr' it prints 'a'.  File: groff.info, Node: troff and nroff Modes, Next: Line Layout, Prev: Character Translations, Up: GNU troff Reference 5.14 'troff' and 'nroff' Modes ============================== Historically, 'nroff' and 'troff' were two separate programs; the former for terminal output, the latter for typesetters. GNU 'troff' merges both functions into one executable(1) (*note troff and nroff Modes-Footnote-1::) that sends its output to a device driver ('grotty' for terminal devices, 'grops' for PostScript, and so on) which interprets this intermediate output format. When discussing AT&T 'troff', it makes sense to talk about "'nroff' mode" and "'troff' mode" since the differences are hard-coded. GNU 'troff' takes information from device and font description files without handling requests specially if a terminal output device is used, so such a strong distinction is unnecessary. Usually, a macro package can be used with all output devices. Nevertheless, it is sometimes necessary to make a distinction between terminal and non-terminal devices: GNU 'troff' provides two built-in conditions 'n' and 't' for the 'if', 'ie', and 'while' requests to decide whether GNU 'troff' shall behave like 'nroff' or like 'troff'. -- Request: .troff Make the 't' built-in condition true (and the 'n' built-in condition false) for 'if', 'ie', and 'while' conditional requests. This is the default if GNU 'troff' (_not_ 'groff') is started with the '-R' switch to avoid loading of the startup files 'troffrc' and 'troffrc-end'. Without '-R', GNU 'troff' stays in 'troff' mode if the output device is not a terminal (e.g., 'ps'). -- Request: .nroff Make the 'n' built-in condition true (and the 't' built-in condition false) for 'if', 'ie', and 'while' conditional requests. This is the default if GNU 'troff' uses a terminal output device; the code for switching to 'nroff' mode is in the file 'tty.tmac', which is loaded by the startup file 'troffrc'. *Note Conditionals and Loops::, for more details on built-in conditions.  File: groff.info, Node: troff and nroff Modes-Footnotes, Up: troff and nroff Modes (1) A GNU 'nroff' program is available for convenience; it calls GNU 'troff' to perform the formatting.  File: groff.info, Node: Line Layout, Next: Line Continuation, Prev: troff and nroff Modes, Up: GNU troff Reference 5.15 Line Layout ================ The following drawing shows the dimensions that 'gtroff' uses for placing a line of output onto the page. They are labeled with the request that manipulates each dimension. -->| in |<-- |<-----------ll------------>| +----+----+----------------------+----+ | : : : | +----+----+----------------------+----+ -->| po |<-- |<--------paper width---------------->| These dimensions are: 'po' "Page offset"--this is the leftmost position of text on the final output, defining the "left margin". 'in' "Indentation"--this is the distance from the left margin where text is printed. 'll' "Line length"--this is the distance from the left margin to right margin. The right margin is not explicitly configured; the combination of page offset and line length provides the information necessary to derive it. A simple demonstration: .ll 3i This is text without indentation. The line length has been set to 3\~inches. .in +.5i .ll -.5i Now the left and right margins are both increased. .in .ll Calling .in and .ll without parameters restores the previous values. => This is text without indenta- => tion. The line length has => been set to 3 inches. => Now the left and => right margins are => both increased. => Calling .in and .ll without => parameters restores the previ- => ous values. -- Request: .po [offset] -- Request: .po +offset -- Request: .po -offset -- Register: \n[.o] Set page offset to OFFSET (or increment or decrement its current value by OFFSET). If invoked without an argument, the page offset is restored to the value before the previous 'po' request. This request does not cause a break; the page offset in effect when an output line is broken prevails (*note Manipulating Filling and Adjustment::). The initial value is 1i and the default scaling unit is 'm'. On terminal devices, the page offset is set to zero by a driver-specific macro file, 'tty.tmac'. The current page offset can be found in the read-only register '.o'. This request is incorrectly documented in the AT&T 'troff' manual as using a default scaling unit of 'v'. .po 3i \n[.o] => 720 .po -1i \n[.o] => 480 .po \n[.o] => 720 -- Request: .in [indent] -- Request: .in +indent -- Request: .in -indent -- Register: \n[.i] Set indentation to INDENT (or increment or decrement the current value by INDENT). This request causes a break. Initially, there is no indentation. If 'in' is called without an argument, the indentation is reset to the previous value before the last call to 'in'. The default scaling unit is 'm'. If a negative indentation value is specified (which is not allowed), 'gtroff' emits a warning in category 'range' and sets the indentation to zero. The effect of 'in' is delayed until a partially collected line (if it exists) is output. A temporary indentation value is reset to zero also. The current indentation (as set by 'in') can be found in the read-only register '.i'. The indentation is associated with the environment (*note Environments::). -- Request: .ti offset -- Request: .ti +offset -- Request: .ti -offset -- Register: \n[.in] Temporarily indent the next output line by OFFSET. If an increment or decrement value is specified, adjust the temporary indentation relative to the value set by the 'in' request. This request causes a break; its value is associated with the environment (*note Environments::). The default scaling unit is 'm'. A call of 'ti' without an argument is ignored. If the total indentation value is negative (which is not allowed), 'gtroff' emits a warning in category 'range' and sets the temporary indentation to zero. 'Total indentation' is either OFFSET if specified as an absolute value, or the temporary plus normal indentation, if OFFSET is given as a relative value. The effect of 'ti' is delayed until a partially collected line (if it exists) is output. The read-only register '.in' is the indentation that applies to the current output line. The difference between '.i' and '.in' is that the latter takes into account whether a partially collected line still uses the old indentation value or a temporary indentation value is active. -- Request: .ll [length] -- Request: .ll +length -- Request: .ll -length -- Register: \n[.l] -- Register: \n[.ll] Set the line length to LENGTH (or increment or decrement the current value by LENGTH). Initially, the line length is set to 6.5i. The effect of 'll' is delayed until a partially collected line (if it exists) is output. The default scaling unit is 'm'. If 'll' is called without an argument, the line length is reset to the previous value before the last call to 'll'. If a negative line length is specified (which is not allowed), 'gtroff' emits a warning in category 'range' and sets the line length to zero. The line length is associated with the environment (*note Environments::). The current line length (as set by 'll') can be found in the read-only register '.l'. The read-only register '.ll' is the line length that applies to the current output line. Similar to '.i' and '.in', the difference between '.l' and '.ll' is that the latter takes into account whether a partially collected line still uses the old line length value.  File: groff.info, Node: Line Continuation, Next: Page Layout, Prev: Line Layout, Up: GNU troff Reference 5.16 Line Continuation ====================== When filling is enabled, input and output line breaks generally do not correspond. The 'roff' language therefore distinguishes input and output line continuation. -- Escape sequence: \ '\' (a backslash immediately followed by a newline) suppresses the effects of that newline in the input. The next input line thus retains the classification of its predecessor as a control or text line. '\' is useful for managing line lengths in the input during document maintenance; you can break an input line in the middle of a request invocation, macro call, or escape sequence. Input line continuation is invisible to the formatter, with two exceptions: the '|' operator recognizes the new input line (*note Numeric Expressions::), and the input line counter register '.c' is incremented. .ll 50n .de I . ft I . nop \\$* . ft .. Our film class watched .I The Effect of Gamma Rays on Man-in-the-Moon Marigolds. \" whoops, the input line wrapped .br .I My own opus begins on line \n[.c] \ and ends on line \n[.c]. => Our film class watched The Effect of Gamma Rays on => Man-in-the-Moon Marigolds. => My own opus begins on line 11 and ends on line 12. -- Escape sequence: \c -- Register: \n[.int] '\c' continues an output line. Nothing after it on the input line is formatted. In contrast to '\', a line after '\c' remains a new input line, so a control character is recognized at its beginning. The visual results depend on whether filling is enabled; see *note Manipulating Filling and Adjustment::. * If filling is enabled, a word interrupted with '\c' is continued with the text on the next input text line, without an intervening space. This is a te\c st. => This is a test. * If filling is disabled, the next input text line after '\c' is handled as a continuation of the same input text line. .nf This is a \c test. => This is a test. An intervening control line that causes a break overrides '\c', flushing out the pending output line in the usual way. The '.int' register contains a positive value if the last output line was continued with '\c'; this datum is associated with the environment (*note Environments::).(1) (*note Line Continuation-Footnote-1::)  File: groff.info, Node: Line Continuation-Footnotes, Up: Line Continuation (1) Historically, the '\c' escape sequence has proven challenging to characterize. Some sources say it "connects the next input text" (to the input line on which it appears); others describe it as "interrupting" text, on the grounds that a text line is interrupted without breaking, perhaps to inject a request invocation or macro call.  File: groff.info, Node: Page Layout, Next: Page Control, Prev: Line Continuation, Up: GNU troff Reference 5.17 Page Layout ================ The formatter permits configuration of the page length and page number. -- Request: .pl [length] -- Request: .pl +length -- Request: .pl -length -- Register: \n[.p] Change (increase or decrease) the page length per the numeric expression LENGTH. The default scaling unit is 'v'. A negative LENGTH is valid, but an uncommon application: it prevents page location traps from being sprung,(1) (*note Page Layout-Footnote-1::) and each output line is placed on a new page. If LENGTH is invalid, GNU 'troff' emits a warning in category 'number'. If LENGTH is absent or invalid, '11i' is assumed. The read-only register '.p' interpolates the current page length. -- Request: .pn num -- Request: .pn +num -- Request: .pn -num -- Register: \n[.pn] Change (increase or decrease) the page number of the _next_ page per the numeric expression NUM. If NUM is invalid, GNU 'troff' emits a warning in category 'number' and ignores the request. Without an argument, 'pn' is ignored. The read-only register '.pn' interpolates NUM if set by 'pn' on the current page, or the current page number plus 1. The formatter offers special support for typesetting headers and footers, collectively termed "titles". Titles have an independent line length, and their placement on the page is not restricted. -- Request: .tl 'left'center'right' Format an output line as a title consisting of LEFT, CENTER, and RIGHT, each aligned accordingly. The delimiter need not be a neutral apostrophe: 'tl' accepts the same delimiters as most escape sequences; see *note Delimiters::. If not used as the delimiter, any "page number character" character is replaced with the current page number; the default is '%'; see the the 'pc' request below. Without an argument, 'tl' is ignored. 'tl' writes the title line immediately, ignoring any partially collected line. It is not an error to omit delimiters after the first. For example, '.tl /Thesis' is interpreted as '.tl /Thesis///': it sets a title line comprising only the left-aligned word 'Thesis'. -- Request: .lt [length] -- Request: .lt +length -- Request: .lt -length -- Register: \n[.lt] Change (increase or decrease) the line length used by titles per the numeric expression LENGTH. The default scaling unit is 'm'. If LENGTH is negative, GNU emits a warning in category 'range' and treats LENGTH as '0'. If LENGTH is invalid, GNU 'troff' emits a warning in category 'number' and ignores the request. The formatter's default title length is '6.5i'. With no argument, the title length is restored to the previous value. The title length is is associated with the environment (*note Environments::). The read-only register '.lt' interpolates the title line length. -- Request: .pc [char] Set the page number character to CHAR. With no argument, the page number character is disabled. 'pc' does not affect the register '%'. The following example exercises title features. .lt 50n This is my partially collected .tl 'Isomers 2023'%'Dextrose Edition' line. => Isomers 2023 1 Dextrose Edition => This is my partially collected line. We most often see titles used in page header and footer traps. *Note Traps::.  File: groff.info, Node: Page Layout-Footnotes, Up: Page Layout (1) *Note Traps::.  File: groff.info, Node: Page Control, Next: Using Fonts, Prev: Page Layout, Up: GNU troff Reference 5.18 Page Control ================= Discretionary page breaks can prevent the unwanted separation of content. A new page number takes effect during page ejection; see *note The Implicit Page Trap::. -- Request: .bp [page-number] -- Request: .bp +page-number -- Request: .bp -page-number -- Register: \n[%] Break the page and change (increase or decrease) the next page number per the numeric expression PAGE-NUMBER. If PAGE-NUMBER is invalid, GNU 'troff' emits a warning in category 'number' and ignores the argument. This request causes a break. A page break advances the vertical drawing position to the bottom of the page, springing traps. *Note Page Location Traps::. 'bp' has effect only if invoked within the top-level diversion.(1) (*note Page Control-Footnote-1::) This request is incorrectly documented in the AT&T 'troff' manual as having a default scaling unit of 'v'. The register '%' interpolates the current page number. .de BP ' bp \" schedule page break once current line is output .. -- Request: .ne [space] Force a page break if insufficient vertical space is available (assert "needed" space). 'ne' tests the distance to the next page location trap; see *note Page Location Traps::, and breaks the page if that amount is less than SPACE. The default scaling unit is 'v'. If SPACE is invalid, GNU 'troff' emits a warning in category 'number' and ignores the argument. If SPACE is not specified, '1v' is assumed. We can require space for at least the first two output lines of a paragraph, preventing its first line from being widowed at the page bottom. .ne 2v Considering how common illness is, how tremendous the spiritual change that it brings, how astonishing, when the lights of health go down, the undiscovered countries that are then disclosed, what wastes and deserts of the soul a slight attack of influenza brings to view, This method is reliable only if no output line is pending when 'ne' is invoked. When macro packages are used, this is often not the case: their paragraphing macros perform the break. You may need to experiment with placing the 'ne' after the paragraphing macro, or 'br' and 'ne' before it. 'ne' is also useful to force grouping of section headings with their subsequent paragraphs, or tables with their captions and/or explanations. Macro packages often use 'ne' with diversions to implement keeps and displays; see *note Diversions::. They may also offer parameters for widow and orphan management. -- Request: .sv [space] -- Request: .os Require vertical space as 'ne' does, but also save it for later output by the 'os' request. If SPACE is available before the next page location trap, it is output immediately. Both requests ignore a partially collected line, taking effect at the next break. 'sv' and 'os' ignore no-space mode (recall *note Manipulating Spacing::). While the 'sv' request allows negative values for SPACE, 'os' ignores them. The default scaling unit is 'v'. If SPACE is not specified, '1v' is assumed. -- Register: \n[nl] 'nl' interpolates or sets the vertical drawing position. When the formatter starts, the first page transition hasn't happened yet, and 'nl' is negative. If a header trap has been planted on the page (typically at vertical position '0'), you can assign a negative value to 'nl' to spring it if that page has already started (*note Page Location Traps::). .de HD . sp . tl ''Goldbach Solution'' . sp .. . First page. .bp .wh 0 HD \" plant header trap at top of page .nr nl (-1) Second page. => First page. => => (blank lines elided) => => Goldbach Solution => => (blank lines elided) => => Second page. Without resetting 'nl' to a negative value, the trap just planted would be active beginning with the _next_ page, not the current one. *Note Diversions::, for a comparison of 'nl' with the '.h' and '.d' registers.  File: groff.info, Node: Page Control-Footnotes, Up: Page Control (1) *Note Diversions::.  File: groff.info, Node: Using Fonts, Next: Manipulating Type Size and Vertical Spacing, Prev: Page Control, Up: GNU troff Reference 5.19 Using Fonts ================ In digital typography, a "font" is a collection of characters in a specific typeface that a device can render as glyphs at a desired size.(1) (*note Using Fonts-Footnote-1::) A 'roff' formatter can change typefaces at any point in the text. The basic faces are a set of "styles" combining upright and slanted shapes with normal and heavy stroke weights: 'R', 'I', 'B', and 'BI'--these stand for roman, italic, bold, and bold-italic. For linguistic text, GNU 'troff' groups typefaces into "families" containing each of these styles.(2) (*note Using Fonts-Footnote-2::) A "text font" is thus often a family combined with a style, but it need not be: consider the 'ps' and 'pdf' devices' 'ZCMI' (Zapf Chancery Medium italic)--often, no other style of Zapf Chancery Medium is provided. On typesetting devices, at least one "special font" is available, comprising "unstyled" glyphs for mathematical operators and other purposes. Like AT&T 'troff', GNU 'troff' does not itself load or manipulate a digital font file;(3) (*note Using Fonts-Footnote-3::) instead it works with a "font description file" that characterizes it, including its glyph repertoire and the "metrics" (dimensions) of each glyph.(4) (*note Using Fonts-Footnote-4::) This information permits the formatter to accurately place glyphs with respect to each other. Before using a font description, the formatter associates it with a "mounting position", a place in an ordered list of available typefaces. So that a document need not be strongly coupled to a specific font family, in GNU 'troff' an output device can associate a style in the abstract sense with a mounting position. Thus the default family can be combined with a style dynamically, producing a "resolved font name". Fonts often have trademarked names, and even Free Software fonts can require renaming upon modification. 'groff' maintains a convention that a device's serif font family is given the name 'T' ("Times"), its sans-serif family 'H' ("Helvetica"), and its monospaced family 'C' ("Courier"). Historical inertia has driven 'groff''s font identifiers to short uppercase abbreviations of font names, as with 'TR', 'TI', 'TB', 'TBI', and a special font 'S'. The default family used with abstract styles can be changed at any time; initially, it is 'T'. Typically, abstract styles are arranged in the first four mounting positions in the order shown above. The default mounting position, and therefore style, is always '1' ('R'). By issuing appropriate formatter instructions, you can override these defaults before your document writes its first glyph. Terminal output devices cannot change font families and lack special fonts. They support style changes by overstriking, or by altering ISO 6429/ECMA-48 "graphic renditions" (character cell attributes). * Menu: * Selecting Fonts:: * Font Families:: * Font Positions:: * Using Symbols:: * Character Classes:: * Special Fonts:: * Artificial Fonts:: * Ligatures and Kerning:: * Italic Corrections:: * Dummy Characters::  File: groff.info, Node: Using Fonts-Footnotes, Up: Using Fonts (1) Terminals and some output devices have fonts that render at only one or two sizes. As examples of the latter, take the 'groff' 'lj4' device's Lineprinter, and 'lbp''s Courier and Elite faces. (2) Font designers prepare families such that the styles share esthetic properties. (3) Historically, the fonts 'troff's dealt with were not Free Software or, as with the Graphic Systems C/A/T, did not even exist in the digital domain. (4) *Note Font Description File Format::.