/usr/share/doc/m4-doc/Index-macro.html

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<a name="Index-macro"></a>
<div class="header">
<p>
Next: <a href="Regexp.html#Regexp" accesskey="n" rel="next">Regexp</a>, Previous: <a href="Len.html#Len" accesskey="p" rel="prev">Len</a>, Up: <a href="Text-handling.html#Text-handling" accesskey="u" rel="up">Text handling</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Searching-for-substrings"></a>
<h3 class="section">11.2 Searching for substrings</h3>

<a name="index-substrings_002c-locating"></a>
<p>Searching for substrings is done with <code>index</code>:
</p>
<dl>
<dt><a name="index-index"></a>Builtin: <strong>index</strong> <em>(<var>string</var>, <var>substring</var>)</em></dt>
<dd><p>Expands to the index of the first occurrence of <var>substring</var> in
<var>string</var>.  The first character in <var>string</var> has index 0.  If
<var>substring</var> does not occur in <var>string</var>, <code>index</code> expands to
&lsquo;<samp>-1</samp>&rsquo;.
</p>
<p>The macro <code>index</code> is recognized only with parameters.
</p></dd></dl>

<div class="example">
<pre class="example">index(`gnus, gnats, and armadillos', `nat')
&rArr;7
index(`gnus, gnats, and armadillos', `dag')
&rArr;-1
</pre></div>

<p>Omitting <var>substring</var> evokes a warning, but still produces output;
contrast this with an empty <var>substring</var>.
</p>
<div class="example">
<pre class="example">index(`abc')
error&rarr;m4:stdin:1: Warning: too few arguments to builtin `index'
&rArr;0
index(`abc', `')
&rArr;0
index(`abc', `b')
&rArr;1
</pre></div>





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m4-doc 1.4.18-1 / usr / share / doc / m4-doc / Index-macro.html
