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diff --git a/doc/groff.html.node/Other-Differences.html b/doc/groff.html.node/Other-Differences.html new file mode 100644 index 0000000..6a92cad --- /dev/null +++ b/doc/groff.html.node/Other-Differences.html @@ -0,0 +1,248 @@ +<!DOCTYPE html> +<html> +<!-- Created by GNU Texinfo 7.0.3, https://www.gnu.org/software/texinfo/ --> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> +<!-- 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". --> +<title>Other Differences (The GNU Troff Manual)</title> + +<meta name="description" content="Other Differences (The GNU Troff Manual)"> +<meta name="keywords" content="Other Differences (The GNU Troff Manual)"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta name="viewport" content="width=device-width,initial-scale=1"> + +<link href="index.html" rel="start" title="Top"> +<link href="Request-Index.html" rel="index" title="Request Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Implementation-Differences.html" rel="up" title="Implementation Differences"> +<link href="Compatibility-Mode.html" rel="prev" title="Compatibility Mode"> +<style type="text/css"> +<!-- +div.example {margin-left: 3.2em} +kbd.key {font-style: normal} +--> +</style> + + +</head> + +<body lang="en"> +<div class="subsection-level-extent" id="Other-Differences"> +<div class="nav-panel"> +<p> +Previous: <a href="Compatibility-Mode.html" accesskey="p" rel="prev">Compatibility Mode</a>, Up: <a href="Implementation-Differences.html" accesskey="u" rel="up">Implementation Differences</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Request-Index.html" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<h4 class="subsection" id="Other-Differences-1">5.38.3 Other Differences</h4> + +<p><code class="code">groff</code> request names unrecognized by other <code class="code">troff</code> +implementations will likely be ignored by them; escape sequences that +are <code class="code">groff</code> extensions are liable to be interpreted as if the +escape character were not present. +<a class="index-entry-id" id="index-_005c_007e_002c-incompatibilities-with-AT_0026T-troff"></a> +For example, the adjustable, non-breaking escape sequence <code class="code">\~</code> +is also supported by Heirloom Doctools <code class="code">troff</code> 050915 (September +2005), <code class="code">mandoc</code> 1.9.5 (2009-09-21), <code class="code">neatroff</code> (commit +1c6ab0f6e, 2016-09-13), and Plan 9 from User Space <code class="code">troff</code> +(commit 93f8143600, 2022-08-12), but not by Solaris or Documenter’s +Workbench <code class="code">troff</code>s. +See <a class="xref" href="Manipulating-Filling-and-Adjustment.html">Manipulating Filling and Adjustment</a>. +</p> +<a class="index-entry-id" id="index-_005cA_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005c_007c_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005c_005e_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005c_0026_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005c_007b_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005c_007d_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005cSP_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005c_0027_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005c_0060_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005c_002d_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005c_005f_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005c_0021_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005c_0025_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005cc_002c-incompatibilities-with-AT_0026T-troff"></a> +<p>GNU <code class="code">troff</code> does not allow the use of the escape sequences +<code class="code">\|</code>, <code class="code">\^</code>, <code class="code">\&</code>, <code class="code">\{</code>, <code class="code">\}</code>, +<code class="code">\<kbd class="key">SP</kbd></code>, <code class="code">\'</code>, <code class="code">\`</code>, <code class="code">\-</code>, <code class="code">\_</code>, <code class="code">\!</code>, +<code class="code">\%</code>, and <code class="code">\c</code> in identifiers; <abbr class="acronym">AT&T</abbr> <code class="code">troff</code> +does. The <code class="code">\A</code> escape sequence (see <a class="pxref" href="Identifiers.html">Identifiers</a>) may be +helpful in avoiding use of these escape sequences in names. +</p> +<a class="index-entry-id" id="index-adjustment-to-both-margins_002c-difference-from-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-rivers"></a> +<p>When adjusting to both margins, <abbr class="acronym">AT&T</abbr> <code class="code">troff</code> at first +adjusts spaces starting from the right; GNU <code class="code">troff</code> begins from +the left. Both implementations adjust spaces from opposite ends on +alternating output lines in this adjustment mode to prevent “rivers” +in the text. +</p> +<a class="index-entry-id" id="index-hyphenation_002c-incompatibilities-with-AT_0026T-troff"></a> +<p>GNU <code class="code">troff</code> does not always hyphenate words as <abbr class="acronym">AT&T</abbr> +<code class="code">troff</code> does. The <abbr class="acronym">AT&T</abbr> implementation uses a set of +hard-coded rules specific to English, while GNU <code class="code">troff</code> uses +language-specific hyphenation pattern files derived from TeX. +Furthermore, in old versions of <code class="code">troff</code> there was a limited amount +of space to store hyphenation exceptions (arguments to the <code class="code">hw</code> +request); GNU <code class="code">troff</code> has no such restriction. +</p> +<a class="index-entry-id" id="index-output-device-name-string-_0028_002eT_0029_002c-in-other-implementations"></a> +<p>GNU <code class="code">troff</code> predefines a string <code class="code">.T</code> containing the argument +given to the <samp class="option">-T</samp> command-line option, namely the current output +device (for example, ‘<samp class="samp">pdf</samp>’ or ‘<samp class="samp">utf8</samp>’). The existence of this +string is a common feature of post-CSTR #54 +<code class="code">troff</code>s<a class="footnote" id="DOCF121" href="groff.html_fot.html#FOOT121"><sup>121</sup></a> but valid values are specific +to each implementation. +</p> +<a class="index-entry-id" id="index-removal-of-read_002donly-registers_002c-incompatibility-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-register_002c-read_002donly_002c-removal_002c-incompatibility-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-read_002donly-register-removal_002c-incompatibility-with-AT_0026T-troff"></a> +<p><abbr class="acronym">AT&T</abbr> <code class="code">troff</code> ignored attempts to remove read-only +registers; GNU <code class="code">troff</code> honors such requests. See <a class="xref" href="Built_002din-Registers.html">Built-in Registers</a>. +</p> +<a class="index-entry-id" id="index-output-device-usage-register-_0028_002eT_0029_002c-incompatibility-with-AT_0026T-troff"></a> +<p>The (read-only) register <code class="code">.T</code> interpolates 1 if GNU +<code class="code">troff</code> is called with the <samp class="option">-T</samp> command-line option, and +0 otherwise. This behavior differs from AT&T <code class="code">troff</code>, which +interpolated 1 only if <code class="code">nroff</code> was the formatter and was +called with <samp class="option">-T</samp>. +</p> +<a class="index-entry-id" id="index-lf-request_002c-incompatibilities-with-AT_0026T-troff"></a> +<p><abbr class="acronym">AT&T</abbr> <code class="code">troff</code> and other implementations handle the +<code class="code">lf</code> request differently. For them, its <var class="var">line</var> argument +changes the line number of the <em class="emph">current</em> line. +</p> +<a class="index-entry-id" id="index-environment-availability-and-naming_002c-incompatibilities-with"></a> +<p><abbr class="acronym">AT&T</abbr> <code class="code">troff</code> had only environments named ‘<samp class="samp">0</samp>’, +‘<samp class="samp">1</samp>’, and ‘<samp class="samp">2</samp>’. In GNU <code class="code">troff</code>, any number of environments +may exist, using any valid identifiers for their names +(see <a class="pxref" href="Identifiers.html">Identifiers</a>.) +</p> +<a class="index-entry-id" id="index-fractional-point-sizes-1"></a> +<a class="index-entry-id" id="index-fractional-type-sizes-1"></a> +<a class="index-entry-id" id="index-point-sizes_002c-fractional-1"></a> +<a class="index-entry-id" id="index-type-sizes_002c-fractional-1"></a> +<a class="index-entry-id" id="index-sizes_002c-fractional"></a> +<a class="index-entry-id" id="index-ps-request_002c-incompatibilities-with-AT_0026T-troff"></a> +<p>Fractional type sizes cause one noteworthy incompatibility. In +<abbr class="acronym">AT&T</abbr> <code class="code">troff</code> the <code class="code">ps</code> request ignores scaling units +and thus ‘<samp class="samp">.ps 10u</samp>’ sets the type size to 10 points, whereas in +GNU <code class="code">troff</code> it sets the type size to 10 <em class="emph">scaled</em> points. +See <a class="xref" href="Using-Fractional-Type-Sizes.html">Using Fractional Type Sizes</a>. +</p> +<a class="index-entry-id" id="index-ab-request_002c-incompatibilities-with-AT_0026T-troff"></a> +<p>The <code class="code">ab</code> request differs from <abbr class="acronym">AT&T</abbr> <code class="code">troff</code>: +GNU <code class="code">troff</code> writes no message to the standard error stream if no +arguments are given, and it exits with a failure status instead of a +successful one. +</p> +<a class="index-entry-id" id="index-bp-request_002c-incompatibilities-with-AT_0026T-troff"></a> +<p>The <code class="code">bp</code> request differs from <abbr class="acronym">AT&T</abbr> <code class="code">troff</code>: +GNU <code class="code">troff</code> does not accept a scaling unit on the argument, a page +number; the former (somewhat uselessly) does. +</p> +<a class="index-entry-id" id="index-pm-request_002c-incompatibilities-with-AT_0026T-troff"></a> +<p>The <code class="code">pm</code> request differs from <abbr class="acronym">AT&T</abbr> <code class="code">troff</code>: +GNU <code class="code">troff</code> reports the sizes of macros, strings, and diversions in +bytes and ignores an argument to report only the sum of the sizes. +</p> +<a class="index-entry-id" id="index-ss-request_002c-incompatibilities-with-AT_0026T-troff"></a> +<p>Unlike <abbr class="acronym">AT&T</abbr> <code class="code">troff</code>, GNU <code class="code">troff</code> does not ignore the +<code class="code">ss</code> request if the output is a terminal device; instead, the +values of minimal inter-word and additional inter-sentence space are +each rounded down to the nearest multiple of 12. +</p> +<a class="index-entry-id" id="index-bd-request_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-cs-request_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-tr-request_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-fp-request_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-input-characters-and-output-glyphs_002c-compatibility-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-output-glyphs_002c-and-input-characters_002c-compatibility-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-characters_002c-input_002c-and-output-glyphs_002c-compatibility-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-glyphs_002c-output_002c-and-input-characters_002c-compatibility-with-AT_0026T-troff"></a> +<p>In GNU <code class="code">troff</code> there is a fundamental difference between +(unformatted) characters and (formatted) glyphs. Everything that +affects how a glyph is output is stored with the glyph node; once a +glyph node has been constructed, it is unaffected by any subsequent +requests that are executed, including <code class="code">bd</code>, <code class="code">cs</code>, <code class="code">tkf</code>, +<code class="code">tr</code>, or <code class="code">fp</code> requests. Normally, glyphs are constructed from +characters immediately before the glyph is added to an output line. +Macros, diversions, and strings are all, in fact, the same type of +object; they contain a sequence of intermixed character and glyph nodes. +Special characters transform from one to the other: before being added +to the output, they behave as characters; afterward, they are glyphs. A +glyph node does not behave like a character node when it is processed by +a macro: it does not inherit any of the special properties that the +character from which it was constructed might have had. For example, +the input +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.di x +\\\\ +.br +.di +.x +</pre></div></div> + +<p>produces ‘<samp class="samp">\\</samp>’ in GNU <code class="code">troff</code>. Each pair of backslashes +becomes one backslash <em class="emph">glyph</em>; the resulting backslashes are thus +not interpreted as escape <em class="emph">characters</em> when they are reread as the +diversion is output. <abbr class="acronym">AT&T</abbr> <code class="code">troff</code> <em class="emph">would</em> interpret +them as escape characters when rereading them and end up printing one +‘<samp class="samp">\</samp>’. +</p> +<a class="index-entry-id" id="index-printing-backslash-_0028_005c_005c_002c-_005ce_002c-_005cE_002c-_005c_005brs_005d_0029"></a> +<a class="index-entry-id" id="index-backslash_002c-printing-_0028_005c_005c_002c-_005ce_002c-_005cE_002c-_005c_005brs_005d_0029"></a> +<a class="index-entry-id" id="index-_005ce_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-_005c_0021_002c-incompatibilities-with-AT_0026T-troff-1"></a> +<a class="index-entry-id" id="index-_005c_003f_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-transparent-output_002c-incompatibilities-with-AT_0026T-troff"></a> +<a class="index-entry-id" id="index-output_002c-transparent_002c-incompatibilities-with-AT_0026T-troff"></a> +<p>One correct way to obtain a printable backslash in most documents is to +use the <code class="code">\e</code> escape sequence; this always prints a single instance +of the current escape character,<a class="footnote" id="DOCF122" href="groff.html_fot.html#FOOT122"><sup>122</sup></a> regardless of whether or not it is used in a diversion; it +also works in both GNU <code class="code">troff</code> and <abbr class="acronym">AT&T</abbr> <code class="code">troff</code>. +</p> +<p>The other correct way, appropriate in contexts independent of the +backslash’s common use as a <code class="code">troff</code> escape character—perhaps in +discussion of character sets or other programming languages—is +the character escape <code class="code">\(rs</code> or <code class="code">\[rs]</code>, for “reverse +solidus”, from its name in the <abbr class="acronym">ECMA-6</abbr> (<abbr class="acronym">ISO/IEC</abbr> 646) +standard.<a class="footnote" id="DOCF123" href="groff.html_fot.html#FOOT123"><sup>123</sup></a> +</p> +<p>To store an escape sequence in a diversion that is interpreted when the +diversion is reread, either use the traditional <code class="code">\!</code> transparent +output facility, or, if this is unsuitable, the new <code class="code">\?</code> escape +sequence. See <a class="xref" href="Diversions.html">Diversions</a> and <a class="ref" href="Gtroff-Internals.html"><code class="code">gtroff</code> Internals</a>. +</p> +<p>In the somewhat pathological case where a diversion exists containing a +partially collected line and a partially collected line at the top-level +diversion has never existed, <abbr class="acronym">AT&T</abbr> <code class="code">troff</code> will output the +partially collected line at the end of input; GNU <code class="code">troff</code> will not. +</p> + + + + +</div> +<hr> +<div class="nav-panel"> +<p> +Previous: <a href="Compatibility-Mode.html">Compatibility Mode</a>, Up: <a href="Implementation-Differences.html">Implementation Differences</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Request-Index.html" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |