'\" t
.TH \%troff 1 "16 October 2023" "groff 1.23.0"
.SH Name
\%troff \- GNU
.I roff
typesetter and document formatter
.
.
.\" ====================================================================
.\" Legal Terms
.\" ====================================================================
.\"
.\" Copyright (C) 1989-2021 Free Software Foundation, Inc.
.\"
.\" This file is part of groff, the GNU roff type-setting system.
.\"
.\" 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, with no Front-Cover Texts,
.\" and with no Back-Cover Texts.
.\"
.\" A copy of the Free Documentation License is included as a file
.\" called FDL in the main directory of the groff source package.
.\"
.\" A copy of the GNU Free Documentation License is also available in this
.\" Debian package as /usr/share/doc/groff-base/copyright.
.
.
.\" Save and disable compatibility mode (for, e.g., Solaris 10/11).
.do nr *groff_troff_1_man_C \n[.cp]
.cp 0
.
.\" Define fallback for groff 1.23's MR macro if the system lacks it.
.nr do-fallback 0
.if !\n(.f           .nr do-fallback 1 \" mandoc
.if  \n(.g .if !d MR .nr do-fallback 1 \" older groff
.if !\n(.g           .nr do-fallback 1 \" non-groff *roff
.if \n[do-fallback]  \{\
.  de MR
.    ie \\n(.$=1 \
.      I \%\\$1
.    el \
.      IR \%\\$1 (\\$2)\\$3
.  .
.\}
.rr do-fallback
.
.
.\" ====================================================================
.SH Synopsis
.\" ====================================================================
.
.SY \%troff
.RB [ \-abcCEiRUz ]
.RB [ \-d\~\c
.IR ctext ]
.RB [ \-d\~\c
.IB string =\c
.IR text ]
.RB [ \-f\~\c
.IR  font-family ]
.RB [ \-F\~\c
.IR  font-directory ]
.RB [ \-I\~\c
.IR  inclusion-directory ]
.RB [ \-m\~\c
.IR  macro-package ]
.RB [ \-M\~\c
.IR  macro-directory ]
.RB [ \-n\~\c
.IR  page-number ]
.RB [ \-o\~\c
.IR  page-list ]
.RB [ \-r\~\c
.IR  cnumeric-expression ]
.RB [ \-r\~\c
.IB register =\c
.IR numeric-expression ]
.RB [ \-T\~\c
.IR  output-device ]
.RB [ \-w\~\c
.IR  warning-category ]
.RB [ \-W\~\c
.IR  warning-category ]
.RI [ file\~ .\|.\|.]
.YS
.
.
.SY \%troff
.B \-\-help
.YS
.
.
.SY \%troff
.B \-v
.
.SY \%troff
.B \-\-version
.YS
.
.
.\" ====================================================================
.SH Description
.\" ====================================================================
.
GNU
.I troff \" GNU
transforms
.MR groff 7
language input into the device-independent output format described in
.MR groff_out 5 ;
.I \%troff
is thus the heart of the GNU
.I roff
document formatting system.
.
If no
.I file
operands are given on the command line,
or if
.I file
is
.RB \[lq] \- \[rq],
the standard input stream is read.
.
.
.P
GNU
.I troff \" GNU
is functionally compatible with the AT&T
.I troff \" AT&T
typesetter and features numerous extensions.
.
Many people prefer to use the
.MR groff 1
command,
a front end which also runs preprocessors and output drivers in the
appropriate order and with appropriate options.
.
.
.\" ====================================================================
.SH Options
.\" ====================================================================
.
.B \-h
and
.B \-\-help
display a usage message,
while
.B \-v
and
.B \-\-version
show version information;
all exit afterward.
.
.
.TP
.B \-a
Generate a plain text approximation of the typeset output.
.
The read-only register
.B .A
is set to\~1.
.
This option produces a sort of abstract preview of the formatted output.
.
.
.RS
.IP \[bu] 2n
Page breaks are marked by a phrase in angle brackets;
for example,
\[lq]<beginning of page>\[rq].
.
.
.IP \[bu]
Lines are broken where they would be in the formatted output.
.
.
.IP \[bu]
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
.B .ss
request)
are not represented.
.
.
.IP \[bu]
Vertical motions are not represented.
.
.
.IP \[bu]
Special characters are rendered in angle brackets;
for example,
the default soft hyphen character appears as
\[lq]<hy>\[rq].
.RE
.
.
.IP
The above description should not be considered a specification;
the details of
.B \-a
output are subject to change.
.
.
.TP
.B \-b
Write a backtrace reporting the state of
.IR \%troff '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
.IR \%troff 's
idea of line numbers can be confused by requests that append to
.\" strings or (??? strings never contain newlines)
macros.
.
.
.TP
.B \-c
Start with color output disabled.
.
.
.TP
.B \-C
Enable AT&T
.I troff \" AT&T
compatibility mode;
implies
.BR \-c .
.
See
.MR groff_diff 7 .
.
.
.TP
.BI \-d\~ ctext
.TQ
.BI \-d\~ string = text
Define
.I roff
.RI string\~ c
or
.I string
as
.I text.
.
.IR c \~must
be one character;
.I string
can be of arbitrary length.
.
Such string assignments happen before any macro file is loaded,
including the startup file.
.
Due to
.MR getopt_long 3
limitations,
.IR c\~ cannot
be,
and
.I string
cannot contain,
an equals sign,
even though that is a valid character in a
.I roff
identifier.
.
.
.TP
.B \-E
Inhibit
.I \%troff
error messages;
implies
.BR \-Ww .
.
This option does
.I not
suppress messages sent to the standard error stream by documents or
macro packages using
.B tm
or related requests.
.
.
.TP
.BI \-f\~ fam
Use
.I fam
as the default font family.
.
.
.TP
.BI \-F\~ dir
Search in directory
.I dir
for the selected output device's directory of device and font
description files.
.
See the description of
.I GROFF_FONT_PATH
in section \[lq]Environment\[rq] below for the default search locations
and ordering.
.
.
.TP
.B \-i
Read the standard input stream after all named input files have been
processed.
.
.
.TP
.BI \-I\~ dir
Search the directory
.I dir
for files
(those named on the command line;
in
.BR psbb ,
.BR so ,
and
.B soquiet
requests;
and in
.RB \[lq] "\[rs]X\[aq]ps: import\[aq]" \[rq],
.RB \[lq] "\[rs]X\[aq]ps: file\[aq]" \[rq],
and
.RB \[lq] "\[rs]X\[aq]pdf: pdfpic\[aq]" \[rq]
device control escape sequences).
.
.B \-I
may be specified more than once;
each
.I dir
is searched in the given order.
.
To search the current working directory before others,
add
.RB \[lq] "\-I .\&" \[rq]
at the desired place;
it is otherwise searched last.
.
.B \-I
works similarly to,
and is named for,
the \[lq]include\[rq]
option of Unix C compilers.
.
.
.TP
.BI \-m\~ name
Process the file
.RI name .tmac
prior to any input files.
.
If not found,
.IR tmac. name
is attempted.
.
.I name
(in both arrangements)
is presumed to be a macro file;
see the description of
.I GROFF_TMAC_PATH
in section \[lq]Environment\[rq] below for the default search locations
and ordering.
.
.
.TP
.BI \-M\~ dir
Search directory
.I dir
for macro files.
.
See the description of
.I GROFF_TMAC_PATH
in section \[lq]Environment\[rq] below for the default search locations
and ordering.
.
.
.TP
.BI \-n\~ num
Begin numbering pages at
.I num.
.
The default
.RB is\~ 1 .
.
.
.TP
.BI \-o\~ list
Output only pages in
.I list,
which is a comma-separated list of inclusive page ranges;
.I n
means page
.I n,
.IB m \- n
means every page
.RI between\~ m
.RI and\~ n ,
.BI \- n
means every page up
.RI to\~ n ,
and
.IB n \-
means every page from
.IR n \~on.
.
.I \%troff
stops processing and exits after formatting the last page enumerated in
.I list.
.
.
.TP
.BI \-r\~ cnumeric-expression
.TQ
.BI \-r\~ register = numeric-expression
Define
.I roff
.RI register\~ c
or
.I register
as
.I numeric-expression.
.
.IR c \~must
be a one-character name;
.I register
can be of arbitrary length.
.
Such register assignments happen before any macro file is loaded,
including the startup file.
.
Due to
.MR getopt_long 3
limitations,
.IR c\~ cannot
be,
and
.I register
cannot contain,
an equals sign,
even though that is a valid character in a
.I roff
identifier.
.
.
.TP
.B \-R
Don't load
.I troffrc
and
.IR troffrc\-end .
.
.
.TP
.BI \-T\~ dev
Prepare output for device
.I dev.
.
The default is
.BR \%ps ;
see
.MR groff 1 .
.
.
.TP
.B \-U
Operate in
.I unsafe mode,
enabling the
.BR open ,
.BR opena ,
.BR pi ,
.BR pso ,
and
.B sy
requests,
which 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
.B \-m
and
.B \-M
options above.
.
.
.TP
.BI \-w\~ name
.TQ
.BI \-W\~ name
Enable
.RB ( \-w )
or inhibit
.RB ( \-W )
warnings in category
.I name.
.
See section \[lq]Warnings\[rq] below.
.
.
.TP
.B \-z
Suppress formatted output.
.
.
.\" ====================================================================
.SH Warnings
.\" ====================================================================
.
.\" BEGIN Keep parallel with groff.texi node "Warnings".
.\" Caveat: the Texinfo manual sorts them by number, not name.
Warning diagnostics emitted by
.I \%troff
are divided into named,
numbered categories.
.
The name associated with each warning category is used by the
.B \-w
and
.B \-W
options.
.
Each category is also assigned a power of two;
the sum of enabled category codes is used by the
.B warn
request and the
.B .warn
register.
.
Warnings of each category are produced under the following
circumstances.
.
.
.P
.TS
tab(@), center, box;
c c c | c c c
r rI lB | r rI lB.
Bit@Code@Category@Bit@Code@Category
_
0@1@char@10@1024@reg
1@2@number@11@2048@tab
2@4@break@12@4096@right\-brace
3@8@delim@13@8192@missing
4@16@el@14@16384@input
5@32@scale@15@32768@escape
6@64@range@16@65536@space
7@128@syntax@17@131072@font
8@256@di@18@262144@ig
9@512@mac@19@524288@color
@@@20@1048576@file
.TE
.
.
.P
.nr x \w'\fBright\-brace'+1n+\w'00000'u
.ta \nxuR
.
.
.TP \nxu+3n
.BR break "\t4"
A filled output line could not be broken such that its length was less
than the output line length
.BR \[rs]n[.l] .
.
This category is enabled by default.
.
.
.TP
.BR char "\t1"
No mounted font defines a glyph for the requested character.
.
This category is enabled by default.
.
.
.TP
.BR color "\t524288"
An undefined color name was selected,
an attempt was made to define a color using an unrecognized color space,
an invalid component in a color definition was encountered,
or an attempt was made to redefine a default color.
.
.
.TP
.BR delim "\t8"
The closing delimiter in an escape sequence was missing or mismatched.
.
.
.TP
.BR di "\t256"
A
.BR di ,
.BR da ,
.BR box ,
or
.B boxa
request was invoked without an argument when there was no current
diversion.
.
.
.TP
.BR el "\t16"
The
.B el
request was encountered with no prior corresponding
.B ie
request.
.
.
.TP
.BR escape "\t32768"
An unsupported escape sequence was encountered.
.
.
.TP
.BR file "\t1048576"
An attempt was made to load a file that does not exist.
.
This category is enabled by default.
.
.
.TP
.BR font "\t131072"
A non-existent font was selected,
or the selection was ignored because a font selection escape sequence
was used after the output line continuation escape sequence on an input
line.
.
This category is enabled by default.
.
.
.TP
.BR ig "\t262144"
An invalid escape sequence occurred in input ignored using the
.B ig
request.
.
This warning category diagnoses a condition that is an error when it
occurs in non-ignored input.
.
.
.TP
.BR input "\t16384"
An invalid character occurred on the input stream.
.
.
.TP
.BR mac "\t512"
An undefined string,
macro,
or diversion was used.
.
When such an object is dereferenced,
an empty one of that name is automatically created.
.
So,
unless it is later deleted,
at most one warning is given for each.
.
.
.IP
This warning is also emitted upon an attempt to move an unplanted trap
macro.
.
In such cases,
the unplanted macro is
.I not
dereferenced,
so it is not created if it does not exist.
.
.
.TP
.BR missing "\t8192"
A request was invoked with a mandatory argument absent.
.
.
.TP
.BR number "\t2"
An invalid numeric expression was encountered.
.
This category is enabled by default.
.
.
.TP
.BR range "\t64"
A numeric expression was out of range for its context.
.
.
.TP
.BR reg "\t1024"
An undefined register was used.
.
When an undefined register is dereferenced,
it is automatically defined with a value of\~0.
.
So,
unless it is later deleted,
at most one warning is given for each.
.
.
.TP
.BR right\-brace "\t4096"
A right brace escape sequence
.B \[rs]}
was encountered where a number was expected.
.
.
.TP
.BR scale "\t32"
A scaling unit inappropriate to its context was used in a numeric
expression.
.
.
.TP
.BR space "\t65536"
A space was missing between a request or macro and its argument.
.
This warning is produced when an undefined name longer than two
characters is encountered and the first two characters of the name
constitute a defined name.
.
No request is invoked,
no macro called,
and an empty macro is not defined.
.
This category is enabled by default.
.
It never occurs in compatibility mode.
.
.
.TP
.BR syntax "\t128"
A self-contradictory hyphenation mode was requested;
an empty or incomplete numeric expression was encountered;
an operand to a numeric operator was missing;
an attempt was made to define a recursive,
empty,
or nonsensical character class;
or a
.I groff
extension conditional expression operator was used while in
compatibility mode.
.
.
.TP
.BR tab "\t2048"
A tab character was encountered where a number was expected,
or appeared in an unquoted macro argument.
.
.
.P
Two warning names group other warning categories for convenience.
.
.
.TP
.B all
All warning categories except
.BR di ,
.BR mac ,
and
.BR reg .
.
This shorthand is intended to produce all warnings that are useful with
macro packages and documents written for AT&T
.I troff \" AT&T
and its descendants,
which have less fastidious diagnostics than GNU
.IR troff . \" GNU
.
.
.TP
.B w
All warning categories.
.
Authors of documents and macro packages targeting
.I groff
are encouraged to use this setting.
.\" END Keep parallel with groff.texi node "Warnings".
.
.
.\" ====================================================================
.SH Environment
.\" ====================================================================
.
.I GROFF_FONT_PATH
and
.I GROFF_TMAC_PATH
each accept a search path of directories;
that is,
a list of directory names separated by the system's path component
separator character.
.
On Unix systems,
this character is a colon (:);
on Windows systems,
it is a semicolon (;).
.
.
.TP
.I GROFF_FONT_PATH
A list of directories in which to seek the selected output device's
directory of device and font description files.
.
.I \%troff
will scan directories given as arguments to any specified
.B \-F
options before these,
then in a site-specific directory
.RI ( /usr/\:\%share/\:\%groff/\:\%site\-font ),
a standard location
.RI ( /usr/\:\%share/\:\%groff/\:\%1.23.0/\:\%font ),
and a compatibility directory
.RI ( /usr/\:\%lib/\:\%font )
after them.
.
.
.TP
.I GROFF_TMAC_PATH
A list of directories in which to search for macro files.
.
.I \%troff
will scan directories given as arguments to any specified
.B \-M
options before these,
then the current directory
(only if in unsafe mode),
the user's home directory,
.if !'no'no' \{\
a platform-specific directory
.RI ( /usr/\:\%lib/\:\%groff/\:\%site\-tmac ),
.\}
a site-specific directory
.RI ( /usr/\:\%share/\:\%groff/\:\%site\-tmac ),
and a standard location
.RI ( /usr/\:\%share/\:\%groff/\:\%1.23.0/\:\%tmac )
after them.
.
.
.TP
.I GROFF_TYPESETTER
Set the default output device.
.
If empty or not set,
.B \%ps
is used.
.
The
.B \-T
option overrides
.IR \%GROFF_TYPESETTER .
.
.
.TP
.I 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
.MR gmtime 3
and
.MR asctime 3
when the formatter starts up and stored in registers usable by documents
and macro packages.
.
.
.TP
.I TZ
The time zone to use when converting the current time to human-readable form;
see
.MR tzset 3 .
If
.I SOURCE_DATE_EPOCH
is used, it is always converted to human-readable form using UTC.
.
.
.\" ====================================================================
.SH Files
.\" ====================================================================
.
.TP
.I /usr/\:\%share/\:\%groff/\:\%1.23.0/\:\%tmac/\:\%troffrc
is an initialization macro file loaded before any macro packages
specified with
.B \-m
options.
.
.
.TP
.I /usr/\:\%share/\:\%groff/\:\%1.23.0/\:\%tmac/\:\%troffrc\-end
is an initialization macro file loaded after all macro packages
specified with
.B \-m
options.
.
.
.TP
.IR /usr/\:\%share/\:\%groff/\:\%1.23.0/\:\%tmac/\: name \:.tmac
are macro files distributed with
.IR groff .
.
.
.TP
.IR /usr/\:\%share/\:\%groff/\:\%1.23.0/\:\%font/\:\%dev name /\:DESC
describes the output device
.IR name .
.
.
.TP
.IR /usr/\:\%share/\:\%groff/\:\%1.23.0/\:\%font/\:\%dev name / F
describes the font
.I F
of device
.I name.
.
.
.P
.I troffrc
and
.I troffrc\-end
are sought neither in the current nor the home directory by default for
security reasons,
even if the
.B \-U
option is specified.
.
Use the
.B \-M
command-line option or the
.I GROFF_TMAC_PATH
environment variable to add these directories to the search path if
necessary.
.
.
.\" ====================================================================
.SH Authors
.\" ====================================================================
.
The GNU version of
.I troff \" generic
was originally written by James Clark;
he also wrote the original version of this document,
which was updated by
.MT wl@\:gnu\:.org
Werner Lemberg
.ME ,
.MT groff\-bernd\:.warken\-72@\:web\:.de
Bernd Warken
.ME ,
and
.MT g.branden\:.robinson@\:gmail\:.com
G.\& Branden Robinson
.ME .
.
.
.\" ====================================================================
.SH "See also"
.\" ====================================================================
.
.IR "Groff: The GNU Implementation of troff" ,
by Trent A.\& Fisher and Werner Lemberg,
is the primary
.I groff
manual.
.
You can browse it interactively with \[lq]info groff\[rq].
.
.
.TP
.MR groff 1
offers an overview of the GNU
.I roff
system
and describes its front end executable.
.
.
.TP
.MR groff 7
details the
.I groff
language,
including a short but complete reference of all predefined requests,
registers,
and escape sequences.
.
.
.TP
.MR groff_char 7
explains the syntax of
.I groff
special character escape sequences,
and lists all special characters predefined by the language.
.
.
.TP
.MR groff_diff 7
enumerates the differences between
AT&T device-independent
.I troff \" AT&T
and
.IR groff .
.
.
.TP
.MR groff_font 5
covers the format of
.I groff
device and font description files.
.
.
.TP
.MR groff_out 5
describes the format of
.IR \%troff 's
output.
.
.
.TP
.MR groff_tmac 5
includes information about macro files that ship with
.IR groff .
.
.
.TP
.MR roff 7
supplies background on
.I roff
systems in general,
including pointers to further related documentation.
.
.
.\" Restore compatibility mode (for, e.g., Solaris 10/11).
.cp \n[*groff_troff_1_man_C]
.do rr *groff_troff_1_man_C
.
.
.\" Local Variables:
.\" fill-column: 72
.\" mode: nroff
.\" End:
.\" vim: set filetype=groff textwidth=72: