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<a name="Format-of-the-Rules-Section"></a>
<h3 class="section">5.2 Format of the Rules Section</h3>

<a name="index-input-file_002c-Rules-Section"></a>
<a name="index-rules_002c-in-flex-input"></a>
<p>The <em>rules</em> section of the <code>flex</code> input contains a series of
rules of the form:
</p>
<div class="example">
<pre class="verbatim">    pattern   action
</pre></div>

<p>where the pattern must be unindented and the action must begin
on the same line.
See <a href="Patterns.html#Patterns">Patterns</a>, for a further description of patterns and actions.
</p>
<p>In the rules section, any indented or %{ %} enclosed text appearing
before the first rule may be used to declare variables which are local
to the scanning routine and (after the declarations) code which is to be
executed whenever the scanning routine is entered.  Other indented or
%{ %} text in the rule section is still copied to the output, but its
meaning is not well-defined and it may well cause compile-time errors
(this feature is present for <acronym>POSIX</acronym> compliance. See <a href="Lex-and-Posix.html#Lex-and-Posix">Lex and Posix</a>, for other such features).
</p>
<p>Any <em>indented</em> text or text enclosed in &lsquo;<samp>%{</samp>&rsquo; and &lsquo;<samp>%}</samp>&rsquo;
is copied verbatim to the output (with the %{ and %} symbols removed).
The %{ and %} symbols must appear unindented on lines by themselves.
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flex-doc 2.6.4-6 / usr / share / doc / flex-doc / html / Rules-Section.html
