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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:44:05 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:44:05 +0000 |
| commit | d318611dd6f23fcfedd50e9b9e24620b102ba96a (patch) | |
| tree | 8b9eef82ca40fdd5a8deeabf07572074c236095d /doc/groff.html.node/Diversions.html | |
| parent | Initial commit. (diff) | |
| download | groff-d318611dd6f23fcfedd50e9b9e24620b102ba96a.tar.xz groff-d318611dd6f23fcfedd50e9b9e24620b102ba96a.zip | |
Adding upstream version 1.23.0.upstream/1.23.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'doc/groff.html.node/Diversions.html')
| -rw-r--r-- | doc/groff.html.node/Diversions.html | 394 |
1 files changed, 394 insertions, 0 deletions
diff --git a/doc/groff.html.node/Diversions.html b/doc/groff.html.node/Diversions.html new file mode 100644 index 0000000..c0dc8e9 --- /dev/null +++ b/doc/groff.html.node/Diversions.html @@ -0,0 +1,394 @@ +<!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>Diversions (The GNU Troff Manual)</title> + +<meta name="description" content="Diversions (The GNU Troff Manual)"> +<meta name="keywords" content="Diversions (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="GNU-troff-Reference.html" rel="up" title="GNU troff Reference"> +<link href="Punning-Names.html" rel="next" title="Punning Names"> +<link href="Traps.html" rel="prev" title="Traps"> +<style type="text/css"> +<!-- +a.copiable-link {visibility: hidden; text-decoration: none; line-height: 0em} +div.example {margin-left: 3.2em} +span.r {font-family: initial; font-weight: normal; font-style: normal} +span:hover a.copiable-link {visibility: visible} +strong.def-name {font-family: monospace; font-weight: bold; font-size: larger} +--> +</style> + + +</head> + +<body lang="en"> +<div class="section-level-extent" id="Diversions"> +<div class="nav-panel"> +<p> +Next: <a href="Punning-Names.html" accesskey="n" rel="next">Punning Names</a>, Previous: <a href="Traps.html" accesskey="p" rel="prev">Traps</a>, Up: <a href="GNU-troff-Reference.html" accesskey="u" rel="up">GNU <code class="code">troff</code> Reference</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> +<h3 class="section" id="Diversions-1">5.29 Diversions</h3> +<a class="index-entry-id" id="index-diversions"></a> + +<p>In <code class="code">roff</code> systems it is possible to format text as if for output, +but instead of writing it immediately, one can <em class="dfn">divert</em> the +formatted text into a named storage area. It is retrieved later by +specifying its name after a control character. The same name space is +used for such <i class="slanted">diversions</i> as for strings and macros; see +<a class="ref" href="Identifiers.html">Identifiers</a>. Such text is sometimes said to be “stored in a +macro”, but this coinage obscures the important distinction between +macros and strings on one hand and diversions on the other; the former +store <em class="emph">unformatted</em> input text, and the latter capture +<em class="emph">formatted</em> output. Diversions also do not interpret arguments. +Applications of diversions include “keeps” (preventing a page break +from occurring at an inconvenient place by forcing a set of output lines +to be set as a group), footnotes, tables of contents, and indices. +<a class="index-entry-id" id="index-top_002dlevel-diversion"></a> +<a class="index-entry-id" id="index-diversion_002c-top_002dlevel"></a> +For orthogonality it is said that GNU <code class="code">troff</code> is in the +<em class="dfn">top-level diversion</em> if no diversion is active (that is, formatted +output is being “diverted” immediately to the output device). +</p> +<p>Dereferencing an undefined diversion will create an empty one of that +name and cause a warning in category ‘<samp class="samp">mac</samp>’ to be emitted. +See <a class="xref" href="Warnings.html">Warnings</a>, for information about the enablement and suppression of +warnings. A diversion does not exist for the purpose of testing with +the <code class="code">d</code> conditional operator until its initial definition ends +(see <a class="pxref" href="Operators-in-Conditionals.html">Operators in Conditionals</a>). The following requests are used to +create and alter diversions. +</p> +<dl class="first-deffn"> +<dt class="deffn" id="index-_002edi"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.di</code></strong> <var class="def-var-arguments">[<span class="r"><i class="slanted">name</i></span>]</var><a class="copiable-link" href='#index-_002edi'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-di"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_002eda"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.da</code></strong> <var class="def-var-arguments">[<span class="r"><i class="slanted">name</i></span>]</var><a class="copiable-link" href='#index-_002eda'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-da"></a> +<a class="index-entry-id" id="index-beginning-diversion-_0028di_002c-box_0029"></a> +<a class="index-entry-id" id="index-diversion_002c-beginning-_0028di_002c-box_0029"></a> +<a class="index-entry-id" id="index-ending-diversion-_0028di_002c-box_0029"></a> +<a class="index-entry-id" id="index-diversion_002c-ending-_0028di_002c-box_0029"></a> +<a class="index-entry-id" id="index-appending-to-a-diversion-_0028da_002c-boxa_0029"></a> +<a class="index-entry-id" id="index-diversion_002c-appending-to-_0028da_002c-boxa_0029"></a> +<p>Start collecting formatted output in a diversion called <var class="var">name</var>. The +<code class="code">da</code> request appends to a diversion called <var class="var">name</var>, creating it +if necessary. If <var class="var">name</var> already exists as an alias, the target of +the alias is replaced or appended to; recall <a class="ref" href="Strings.html">Strings</a>. The pending +output line is diverted as well. Switching to another environment (with +the <code class="code">ev</code> request) before invoking <code class="code">di</code> or <code class="code">da</code> avoids +including any pending output line in the diversion; see +<a class="ref" href="Environments.html">Environments</a>. +</p> +<p>Invoking <code class="code">di</code> or <code class="code">da</code> without an argument stops diverting +output to the diversion named by the most recent corresponding request. +If <code class="code">di</code> or <code class="code">da</code> is called without an argument when there is no +current diversion, a warning in category ‘<samp class="samp">di</samp>’ is produced. +See <a class="xref" href="Warnings.html">Warnings</a>, for information about the enablement and suppression +of warnings. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">Before the diversion. +.di yyy +In the diversion. +.br +.di +After the diversion. +.br + ⇒ After the diversion. +.yyy + ⇒ Before the diversion. In the diversion. +</pre></div></div> +</dd></dl> + +<a class="index-entry-id" id="index-box-_0028diversion-operation_0029"></a> +<p>GNU <code class="code">troff</code> supports <em class="dfn">box</em> requests to exclude a partially +collected line from a diversion, as this is often desirable. +</p> +<dl class="first-deffn"> +<dt class="deffn" id="index-_002ebox"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.box</code></strong> <var class="def-var-arguments">[<span class="r"><i class="slanted">name</i></span>]</var><a class="copiable-link" href='#index-_002ebox'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-box"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_002eboxa"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.boxa</code></strong> <var class="def-var-arguments">[<span class="r"><i class="slanted">name</i></span>]</var><a class="copiable-link" href='#index-_002eboxa'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-boxa"></a> +<p>Divert (or append) output to <var class="var">name</var>, similarly to the <code class="code">di</code> and +<code class="code">da</code> requests, respectively. Any pending output line is <em class="emph">not</em> +included in the diversion. Without an argument, stop diverting output; +any pending output line inside the diversion is discarded. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">Before the box. +.box xxx +In the box. +.br +Hidden treasure. +.box +After the box. +.br + ⇒ Before the box. After the box. +.xxx + ⇒ In the box. +</pre></div></div> +</dd></dl> + +<p>Apart from pending output line inclusion and the request names that +populate them, boxes are handled exactly as diversions are. All of the +following <code class="code">groff</code> language elements can be used with them +interchangeably. +</p> +<dl class="first-deffn"> +<dt class="deffn" id="index-_005cn_005b_002ez_005d"><span class="category-def">Register: </span><span><strong class="def-name"><code class="t">\n[.z]</code></strong><a class="copiable-link" href='#index-_005cn_005b_002ez_005d'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_002ez"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_005cn_005b_002ed_005d"><span class="category-def">Register: </span><span><strong class="def-name"><code class="t">\n[.d]</code></strong><a class="copiable-link" href='#index-_005cn_005b_002ed_005d'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_002ed"></a> +<a class="index-entry-id" id="index-nl-register_002c-and-_002ed"></a> +<a class="index-entry-id" id="index-nested-diversions"></a> +<a class="index-entry-id" id="index-diversion_002c-nested"></a> +<a class="index-entry-id" id="index-diversion-name-register-_0028_002ez_0029"></a> +<a class="index-entry-id" id="index-vertical-position-in-diversion-register-_0028_002ed_0029"></a> +<a class="index-entry-id" id="index-position_002c-vertical_002c-in-diversion_002c-register-_0028_002ed_0029"></a> +<a class="index-entry-id" id="index-diversion_002c-vertical-position-in_002c-register-_0028_002ed_0029"></a> +<p>Diversions may be nested. The read-only string-valued register +<code class="code">.z</code> contains the name of the current diversion. The read-only +register <code class="code">.d</code> contains the current vertical place in the diversion. +If the input text is not being diverted, <code class="code">.d</code> reports the same +location as the register <code class="code">nl</code>. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_005cn_005b_002eh_005d"><span class="category-def">Register: </span><span><strong class="def-name"><code class="t">\n[.h]</code></strong><a class="copiable-link" href='#index-_005cn_005b_002eh_005d'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_002eh"></a> +<a class="index-entry-id" id="index-high_002dwater-mark-register-_0028_002eh_0029"></a> +<a class="index-entry-id" id="index-mark_002c-high_002dwater_002c-register-_0028_002eh_0029"></a> +<a class="index-entry-id" id="index-position-of-lowest-text-line-_0028_002eh_0029"></a> +<a class="index-entry-id" id="index-text-line_002c-position-of-lowest-_0028_002eh_0029"></a> +<p>The read-only register <code class="code">.h</code> stores the <em class="dfn">high-water mark</em> on the +current page or in the current diversion. It corresponds to the text +baseline of the lowest line on the page.<a class="footnote" id="DOCF113" href="groff.html_fot.html#FOOT113"><sup>113</sup></a> +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.tm .h==\n[.h], nl==\n[nl] + ⇒ .h==0, nl==-1 +This is a test. +.br +.sp 2 +.tm .h==\n[.h], nl==\n[nl] + ⇒ .h==40, nl==120 +</pre></div></div> + +<a class="index-entry-id" id="index-_002eh-register_002c-difference-from-nl"></a> +<a class="index-entry-id" id="index-nl-register_002c-difference-from-_002eh"></a> +<p>As implied by the example, vertical motion does not produce text +baselines and thus does not increase the value interpolated by +‘<samp class="samp">\n[.h]</samp>’. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_005cn_005bdn_005d"><span class="category-def">Register: </span><span><strong class="def-name"><code class="t">\n[dn]</code></strong><a class="copiable-link" href='#index-_005cn_005bdn_005d'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-dn"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_005cn_005bdl_005d"><span class="category-def">Register: </span><span><strong class="def-name"><code class="t">\n[dl]</code></strong><a class="copiable-link" href='#index-_005cn_005bdl_005d'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-dl"></a> +<a class="index-entry-id" id="index-dn-register_002c-and-da-_0028boxa_0029"></a> +<a class="index-entry-id" id="index-dl-register_002c-and-da-_0028boxa_0029"></a> +<a class="index-entry-id" id="index-da-request_002c-and-dn-_0028dl_0029"></a> +<a class="index-entry-id" id="index-boxa-request_002c-and-dn-_0028dl_0029"></a> +<p>After completing a diversion, the writable registers <code class="code">dn</code> and +<code class="code">dl</code> contain its vertical and horizontal sizes. Only the lines +just processed are counted: for the computation of <code class="code">dn</code> and +<code class="code">dl</code>, the requests <code class="code">da</code> and <code class="code">boxa</code> are handled as if +<code class="code">di</code> and <code class="code">box</code> had been used, respectively—lines that have +been already stored in the diversion (box) are not taken into account. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.\" Center text both horizontally and vertically. +.\" Macro .(c starts centering mode; .)c terminates it. +. +.\" Disable the escape character with .eo so that we +.\" don't have to double backslashes on the "\n"s. +.eo +.de (c +. br +. ev (c +. evc 0 +. in 0 +. nf +. di @c +.. +</pre></div></div> +<div class="example"> +<div class="group"><pre class="example-preformatted">.de )c +. br +. ev +. di +. nr @s (((\n[.t]u - \n[dn]u) / 2u) - 1v) +. sp \n[@s]u +. ce 1000 +. @c +. ce 0 +. sp \n[@s]u +. br +. fi +. rr @s +. rm @c +.. +.ec +</pre></div></div> +</dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_005c_0021anything"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\!</code><span class="r"><i class="slanted">anything</i></span><code class="t"></code></strong><a class="copiable-link" href='#index-_005c_0021anything'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_005c_0021"></a> +</dd><dt class="deffnx def-cmd-deffn" id="index-_005c_003fanything_005c_003f"><span class="category-def">Escape sequence: </span><span><strong class="def-name"><code class="t">\?</code><span class="r"><i class="slanted">anything</i></span><code class="t">\?</code></strong><a class="copiable-link" href='#index-_005c_003fanything_005c_003f'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-_005c_003f"></a> +<a class="index-entry-id" id="index-transparent-output-_0028_005c_0021_002c-_005c_003f_0029"></a> +<a class="index-entry-id" id="index-output_002c-transparent-_0028_005c_0021_002c-_005c_003f_0029"></a> +<p><em class="dfn">Transparently</em> embed <var class="var">anything</var> into the current diversion, +preventing requests, macro calls, and escape sequences from being +interpreted when read into a diversion. This is useful for preventing +them from taking effect until the diverted text is actually output. The +<code class="code">\!</code> escape sequence transparently embeds input up to and including +the end of the line. The <code class="code">\?</code> escape sequence transparently embeds +input until its own next occurrence. +</p> +<a class="index-entry-id" id="index-_005c_003f_002c-and-copy-mode-1"></a> +<a class="index-entry-id" id="index-copy-mode_002c-and-_005c_003f-1"></a> +<a class="index-entry-id" id="index-mode_002c-copy_002c-and-_005c_003f-1"></a> +<a class="index-entry-id" id="index-_005c_0021_002c-and-copy-mode"></a> +<a class="index-entry-id" id="index-copy-mode_002c-and-_005c_0021"></a> +<a class="index-entry-id" id="index-mode_002c-copy_002c-and-_005c_0021"></a> +<p><var class="var">anything</var> may not contain newlines; use <code class="code">\!</code> by itself to +embed newlines in a diversion. The escape sequence <code class="code">\?</code> is also +recognized in copy mode and turned into a single internal code; it is +this code that terminates <var class="var">anything</var>. Thus the following example +prints 4. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.nr x 1 +.nf +.di d +\?\\?\\\\?\\\\\\\\nx\\\\?\\?\? +.di +.nr x 2 +.di e +.d +.di +.nr x 3 +.di f +.e +.di +.nr x 4 +.f +</pre></div></div> + +<p>Both escape sequences read the data in copy mode. +</p> +<a class="index-entry-id" id="index-_005c_0021_002c-in-top_002dlevel-diversion"></a> +<a class="index-entry-id" id="index-top_002dlevel-diversion_002c-and-_005c_0021"></a> +<a class="index-entry-id" id="index-diversion_002c-top_002dlevel_002c-and-_005c_0021"></a> +<p>If <code class="code">\!</code> is used in the top-level diversion, its argument is +directly embedded into GNU <code class="code">troff</code>’s intermediate output. This can +be used, for example, to control a postprocessor that processes the data +before it is sent to an output driver. +</p> +<a class="index-entry-id" id="index-_005c_003f_002c-in-top_002dlevel-diversion"></a> +<a class="index-entry-id" id="index-top_002dlevel-diversion_002c-and-_005c_003f"></a> +<a class="index-entry-id" id="index-diversion_002c-top_002dlevel_002c-and-_005c_003f"></a> +<p>The <code class="code">\?</code> escape used in the top-level diversion produces no output +at all; its argument is simply ignored. +</p></dd></dl> + +<a class="index-entry-id" id="index-_005c_0021_002c-and-output-request"></a> +<a class="index-entry-id" id="index-output-request_002c-and-_005c_0021"></a> +<a class="index-entry-id" id="index-output-request_002c-and-copy-mode"></a> +<a class="index-entry-id" id="index-copy-mode_002c-and-output-request"></a> +<a class="index-entry-id" id="index-mode_002c-copy_002c-and-output-request"></a> +<dl class="first-deffn"> +<dt class="deffn" id="index-_002eoutput"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.output</code></strong> <var class="def-var-arguments">contents</var><a class="copiable-link" href='#index-_002eoutput'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-output"></a> +<p>Emit <var class="var">contents</var> directly to GNU <code class="code">troff</code>’s intermediate output +(subject to copy mode interpretation); this is similar to <code class="code">\!</code> used +at the top level. An initial neutral double quote in <var class="var">contents</var> is +stripped to allow embedding of leading spaces. +</p> +<p>This request can’t be used before the first page has started—if you +get an error, simply insert <code class="code">.br</code> before the <code class="code">output</code> request. +</p> +<p>Use with caution! It is normally only needed for mark-up used by a +postprocessor that does something with the output before sending it to +the output device, filtering out <var class="var">contents</var> again. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_002easciify"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.asciify</code></strong> <var class="def-var-arguments">div</var><a class="copiable-link" href='#index-_002easciify'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-asciify"></a> +<a class="index-entry-id" id="index-unformatting-diversions-_0028asciify_0029"></a> +<a class="index-entry-id" id="index-diversion_002c-unformatting-_0028asciify_0029"></a> +<a class="index-entry-id" id="index-trin-request_002c-and-asciify"></a> +<p><em class="dfn">Unformat</em> the diversion <var class="var">div</var> in a way such that Unicode basic +Latin (<abbr class="acronym">ASCII</abbr>) characters, characters translated with the +<code class="code">trin</code> request, space characters, and some escape sequences, that +were formatted and diverted into <var class="var">div</var> are treated like ordinary +input characters when <var class="var">div</var> is reread. Doing so can be useful in +conjunction with the <code class="code">writem</code> request. <code class="code">asciify</code> can be also +used for gross hacks; for example, the following sets +register <code class="code">n</code> to 1. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.tr @. +.di x +@nr n 1 +.br +.di +.tr @@ +.asciify x +.x +</pre></div></div> + +<p><code class="code">asciify</code> cannot return all items in a diversion to their source +equivalent: nodes such as those produced by the <code class="code">\N</code> escape +sequence will remain nodes, so the result cannot be guaranteed to be a +pure string. See <a class="xref" href="Copy-Mode.html">Copy Mode</a>. Glyph parameters such as the type face +and size are not preserved; use <code class="code">unformat</code> to achieve that. +</p></dd></dl> + +<dl class="first-deffn"> +<dt class="deffn" id="index-_002eunformat"><span class="category-def">Request: </span><span><strong class="def-name"><code class="t">.unformat</code></strong> <var class="def-var-arguments">div</var><a class="copiable-link" href='#index-_002eunformat'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-unformat"></a> +<p>Like <code class="code">asciify</code>, unformat the diversion <var class="var">div</var>. However, +<code class="code">unformat</code> handles only tabs and spaces between words, the latter +usually arising from spaces or newlines in the input. Tabs are treated +as input tokens, and spaces become adjustable again. The vertical sizes +of lines are not preserved, but glyph information (font, type size, +space width, and so on) is retained. +</p></dd></dl> + + + +</div> +<hr> +<div class="nav-panel"> +<p> +Next: <a href="Punning-Names.html">Punning Names</a>, Previous: <a href="Traps.html">Traps</a>, Up: <a href="GNU-troff-Reference.html">GNU <code class="code">troff</code> Reference</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> |