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<title>Meta-characters</title>
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<h2 class="title">Meta-characters</h2>
<p class="para">
The power of regular expressions comes from the
ability to include alternatives and repetitions in the
pattern. These are encoded in the pattern by the use of
<em class="emphasis">meta-characters</em>, which do not stand for themselves but instead
are interpreted in some special way.
</p>
<p class="para">
There are two different sets of meta-characters: those that
are recognized anywhere in the pattern except within square
brackets, and those that are recognized in square brackets.
Outside square brackets, the meta-characters are as follows:
<table class="doctable table">
<caption><strong>Meta-characters outside square brackets</strong></caption>
<thead>
<tr>
<th>Meta-character</th><th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>\</td><td>general escape character with several uses</td>
</tr>
<tr>
<td>^</td><td>assert start of subject (or line, in multiline mode)</td>
</tr>
<tr>
<td>$</td><td>assert end of subject or before a terminating newline (or end of line, in multiline mode)</td>
</tr>
<tr>
<td>.</td><td>match any character except newline (by default)</td>
</tr>
<tr>
<td>[</td><td>start character class definition</td>
</tr>
<tr>
<td>]</td><td>end character class definition</td>
</tr>
<tr>
<td>|</td><td>start of alternative branch</td>
</tr>
<tr>
<td>(</td><td>start subpattern</td>
</tr>
<tr>
<td>)</td><td>end subpattern</td>
</tr>
<tr>
<td>?</td><td>extends the meaning of (, also 0 or 1 quantifier, also makes greedy
quantifiers lazy (see <a href="regexp.reference.repetition.html" class="link">repetition</a>)</td>
</tr>
<tr>
<td>*</td><td>0 or more quantifier</td>
</tr>
<tr>
<td>+</td><td>1 or more quantifier</td>
</tr>
<tr>
<td>{</td><td>start min/max quantifier</td>
</tr>
<tr>
<td>}</td><td>end min/max quantifier</td>
</tr>
</tbody>
</table>
Part of a pattern that is in square brackets is called a
<a href="regexp.reference.character-classes.html" class="link">character class</a>. In a character class the only
meta-characters are:
<table class="doctable table">
<caption><strong>Meta-characters inside square brackets (<em class="emphasis">character classes</em>)</strong></caption>
<thead>
<tr>
<th>Meta-character</th><th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>\</td><td>general escape character</td>
</tr>
<tr>
<td>^</td><td>negate the class, but only if the first character</td>
</tr>
<tr>
<td>-</td><td>indicates character range</td>
</tr>
</tbody>
</table>
The following sections describe the use of each of the
meta-characters.
</p>
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