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<title>Invoking Requests (The GNU Troff Manual)</title>
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<hr>
<h4 class="subsection" id="Invoking-Requests-1">5.6.2 Invoking Requests</h4>
<a class="index-entry-id" id="index-invoking-requests"></a>
<a class="index-entry-id" id="index-requests_002c-invoking"></a>
<p>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 <code class="code">rm</code> request makes it unavailable. The
<code class="code">als</code> request can alias requests, permitting them to be wrapped or
non-destructively replaced. See <a class="xref" href="Strings.html">Strings</a>.
</p>
<a class="index-entry-id" id="index-request-arguments"></a>
<a class="index-entry-id" id="index-arguments-to-requests"></a>
<a class="index-entry-id" id="index-tabs_002c-and-macro-arguments"></a>
<a class="index-entry-id" id="index-macro-arguments_002c-and-tabs"></a>
<a class="index-entry-id" id="index-arguments-to-macros_002c-and-tabs"></a>
<a class="index-entry-id" id="index-tabs_002c-and-request-arguments"></a>
<a class="index-entry-id" id="index-request-arguments_002c-and-tabs"></a>
<a class="index-entry-id" id="index-arguments-to-requests_002c-and-tabs"></a>
<p>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 <code class="code">troff</code>
does not allow tabs for argument separation.<a class="footnote" id="DOCF43" href="groff.html_fot.html#FOOT43"><sup>43</sup></a>
</p>
<p>Generally, a space <em class="emph">within</em> a request argument is not relevant, not
meaningful, or is supported by bespoke provisions, as with the <code class="code">tl</code>
request’s delimiters (see <a class="pxref" href="Page-Layout.html">Page Layout</a>). Some requests, like
<code class="code">ds</code>, interpret the remainder of the control line as a single
argument. See <a class="xref" href="Strings.html">Strings</a>.
</p>
<a class="index-entry-id" id="index-structuring-source-code-of-documents-or-macro-packages"></a>
<a class="index-entry-id" id="index-documents_002c-structuring-the-source-of"></a>
<a class="index-entry-id" id="index-macro-package_002c-structuring-the-source-of"></a>
<a class="index-entry-id" id="index-package_002c-package_002c-structuring-the-source-of"></a>
<a class="index-entry-id" id="index-indentation_002c-of-roff-source-code"></a>
<p>Spaces and tabs immediately after a control character are ignored.
Commonly, authors structure the source of documents or macro files with
them.
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">.de center
. if \\n[.br] \
. br
. ce \\$1
..
.
.
.de right-align
.→if \\n[.br] \
.→→br
.→rj \\$1
..
</pre></div></div>
<a class="index-entry-id" id="index-blank-line-trap-_0028blm_0029"></a>
<a class="index-entry-id" id="index-blank-line-macro-_0028blm_0029-1"></a>
<p>If you assign an empty blank line trap, you can separate macro
definitions (or any input lines) with blank lines.
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">.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
</pre></div></div>
<p>See <a class="xref" href="Blank-Line-Traps.html">Blank Line Traps</a>.
</p>
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