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<title>Appendix E. Regular Expressions</title><meta name="generator" content="DocBook XSL Stylesheets V1.79.1"><link rel="home" href="index.html" title="jEdit 5.6 User's Guide"><link rel="up" href="using-jedit-part.html" title="Part I. Using jEdit"><link rel="prev" href="globs.html" title="Appendix D. Glob Patterns"><link rel="next" href="macro-index.html" title="Appendix F. Macros Included With jEdit"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Appendix E. Regular Expressions</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="globs.html">Prev</a> </td><th width="60%" align="center">Part I. Using jEdit</th><td width="20%" align="right"> <a accesskey="n" href="macro-index.html">Next</a></td></tr></table><hr></div><div class="appendix"><div class="titlepage"><div><div><h2 class="title"><a name="regexps"></a>Appendix E. Regular Expressions</h2></div></div></div><p>jEdit uses regular expressions from <a class="ulink" href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/regex/Pattern.html" target="_top">java.util.regex.Pattern</a>
to implement inexact search and replace. Click there to see a complete
reference guide to all supported meta-characters.</p><p>A regular expression consists of a string where some characters are
given special meaning with regard to pattern matching.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Inside XML files</h3><p>Inside XML files (such as jEdit mode files), it is important that
you escape XML special characters, such as &, <, >, etc. You
can use the XML plugin's "characters to entities" to perform this
mapping.</p></div><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Inside Java / beanshell / properties files</h3><p>Java strings are always parsed by java before they are processed
by the regular expression engine, so you must make sure that backslashes
are escaped by an extra backslash (<code class="literal">\\</code>)</p></div><p>Within a regular expression, the following characters have special
meaning:</p><h2><a name="d0e8102"></a>Positional Operators</h2><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="literal">^</code> matches at the beginning of a line</p></li><li class="listitem"><p><code class="literal">$</code> matches at the end of a line</p></li><li class="listitem"><p><code class="literal">\b</code> matches at a word boundary</p></li><li class="listitem"><p><code class="literal">\B</code> matches at a non-word break</p></li><li class="listitem"><p><code class="literal">\A</code> The beginning of the input</p></li><li class="listitem"><p><code class="literal">\G</code> The end of the previous match</p></li><li class="listitem"><p><code class="literal">\Z</code> The end of the input but for the final terminator, if any</p></li><li class="listitem"><p><code class="literal">\z</code> The end of the input</p></li></ul></div><h2><a name="d0e8145"></a>One-Character Operators</h2><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="literal">.</code> matches any single character (may or may not match line terminators)</p></li><li class="listitem"><p><code class="literal">\d</code> matches any decimal digit (<code class="literal">[0-9]</code>)</p></li><li class="listitem"><p><code class="literal">\D</code> matches any non-digit (<code class="literal">[^0-9]</code>)</p></li><li class="listitem"><p><code class="literal">\n</code> matches the newline character (<code class="literal">\u000A</code>)</p></li><li class="listitem"><p><code class="literal">\s</code> matches any whitespace character (<code class="literal">[ \t\n\x0B\f\r]</code>)</p></li><li class="listitem"><p><code class="literal">\x<em class="replaceable"><code>hh</code></em></code> matches hexadecimal character code <code class="literal">0xhh</code></p></li><li class="listitem"><p><code class="literal">\S</code> matches any non-whitespace character (<code class="literal">[^\s]</code>)</p></li><li class="listitem"><p><code class="literal">\t</code> matches a horizontal tab character (<code class="literal">\u0009</code>)</p></li><li class="listitem"><p><code class="literal">\w</code> matches any word character (<code class="literal">[a-zA-Z_0-9]</code>)</p></li><li class="listitem"><p><code class="literal">\W</code> matches any non-word character (<code class="literal">[^\w]</code>)</p></li><li class="listitem"><p><code class="literal">\\</code> matches the backslash character (<span class="quote">“<span class="quote">\</span>”</span>)</p></li></ul></div><h2><a name="d0e8234"></a>Character Class Operator</h2><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="literal">[<em class="replaceable"><code>abc</code></em>]</code> matches
any character in the set <em class="replaceable"><code>a</code></em>,
<em class="replaceable"><code>b</code></em> or <em class="replaceable"><code>c</code></em>.
A leading <span class="quote">“<span class="quote">]</span>”</span> will be interpreted literally.</p></li><li class="listitem"><p><code class="literal">[^<em class="replaceable"><code>abc</code></em>]</code> matches
any character not in the set <em class="replaceable"><code>a</code></em>,
<em class="replaceable"><code>b</code></em> or <em class="replaceable"><code>c</code></em>.
A leading <span class="quote">“<span class="quote">]</span>”</span> after the <span class="quote">“<span class="quote">^</span>”</span>
will be interpreted literally.</p></li><li class="listitem"><p><code class="literal">[<em class="replaceable"><code>a-zA-Z</code></em>]</code> matches
any character in the ranges <em class="replaceable"><code>a</code></em> to
<em class="replaceable"><code>z</code></em> and <em class="replaceable"><code>A</code></em> to
<em class="replaceable"><code>Z</code></em>, inclusive. A leading or trailing dash
and a leading <span class="quote">“<span class="quote">]</span>”</span> will be interpreted literally.</p></li></ul></div><h2><a name="d0e8303"></a>Subexpressions and Backreferences</h2><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="literal">(<em class="replaceable"><code>abc</code></em>)</code> matches
whatever the expression <em class="replaceable"><code>abc</code></em> would match,
and saves it as a subexpression. Also used for grouping</p></li><li class="listitem"><p><code class="literal">(?<<em class="replaceable"><code>name</code></em>><em class="replaceable"><code>abc</code></em>)</code>
matches whatever the expression <em class="replaceable"><code>abc</code></em> would match,
and saves it as a subexpression called <em class="replaceable"><code>name</code></em>.
Also used for grouping</p></li><li class="listitem"><p><code class="literal">(?:<em class="replaceable"><code>...</code></em>)</code> pure
grouping operator, does not save contents</p></li><li class="listitem"><p><code class="literal">(?=<em class="replaceable"><code>...</code></em>)</code> positive
lookahead; the regular expression will match if the text in the
brackets matches, but that text will not be considered part of the
match</p></li><li class="listitem"><p><code class="literal">(?!<em class="replaceable"><code>...</code></em>)</code> negative
lookahead; the regular expression will match if the text in the
brackets does not match, and that text will not be considered part
of the match</p></li><li class="listitem"><p><code class="literal">(?<=<em class="replaceable"><code>...</code></em>)</code> positive
lookbehind; the regular expression will match if the text in the
brackets matches, but that text will not be considered part of the
match</p></li><li class="listitem"><p><code class="literal">(?<!<em class="replaceable"><code>...</code></em>)</code> negative
lookbehind; the regular expression will match if the text in the
brackets does not match, and that text will not be considered part
of the match</p></li><li class="listitem"><p><code class="literal">(?><em class="replaceable"><code>...</code></em>)</code> pure
possessive grouping operator, does not save contents and does not
back off during backtracking</p></li><li class="listitem"><p><code class="literal">\<em class="replaceable"><code>n</code></em></code> where 0 <
<em class="replaceable"><code>n</code></em> < 10, matches the same thing the
<em class="replaceable"><code>n</code></em>th subexpression matched. Can only be
used in the search string</p></li><li class="listitem"><p><code class="literal">$<em class="replaceable"><code>n</code></em></code> where 0 <
<em class="replaceable"><code>n</code></em> < 10, substituted with the text
matched by the <em class="replaceable"><code>n</code></em>th subexpression. Can
only be used in the replacement string</p></li><li class="listitem"><p><code class="literal">\k<<em class="replaceable"><code>name</code></em>></code>,
matches the same thing the subexpression called <em class="replaceable"><code>name</code></em>
matched. Can only be used in the search string</p></li><li class="listitem"><p><code class="literal">${<em class="replaceable"><code>name</code></em>}</code>,
substituted with the text matched by the subexpression called <em class="replaceable"><code>name</code></em>.
Can only be used in the replacement string</p></li></ul></div><h2><a name="d0e8430"></a>Branching (Alternation) Operator</h2><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="literal"><em class="replaceable"><code>a</code></em>|<em class="replaceable"><code>b</code></em></code>
matches whatever the expression <em class="replaceable"><code>a</code></em> would
match, or whatever the expression <em class="replaceable"><code>b</code></em> would
match.</p></li></ul></div><h2><a name="d0e8448"></a>Repeating Operators</h2><p>These symbols operate on the previous atomic expression.</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="literal">?</code> matches the preceding expression once or not at all</p></li><li class="listitem"><p><code class="literal">*</code> matches the preceding expression zero or more times</p></li><li class="listitem"><p><code class="literal">+</code> matches the preceding expression one or more times</p></li><li class="listitem"><p><code class="literal">{<em class="replaceable"><code>n</code></em>}</code>matches the preceding expression
exactly <em class="replaceable"><code>n</code></em> times</p></li><li class="listitem"><p><code class="literal">{<em class="replaceable"><code>n</code></em>,<em class="replaceable"><code>m</code></em>}</code>
matches the preceding expression between <em class="replaceable"><code>n</code></em> and
<em class="replaceable"><code>m</code></em> times, inclusive</p></li><li class="listitem"><p><code class="literal">{<em class="replaceable"><code>n</code></em>,}</code> matches
the preceding expression <em class="replaceable"><code>n</code></em> or more times</p></li></ul></div><h2><a name="d0e8507"></a>Greedy, Reluctant and Possessive Matching</h2><p>If a repeating operator (above) is immediately followed by a
<code class="literal">?</code>, it behaves reluctant, that is
the repeating operator will stop at the smallest
number of repetitions that can complete the rest of the match.</p><p>If a repeating operator (above) is immediately followed by a
<code class="literal">+</code>, it behaves possessive, that is
the repeating operator will match as much characters as it can
and will not back off during backtracking,
even if that would allow to complete the rest of the match.</p><p>If a repeating operator (above) is not immediately followed by a
<code class="literal">?</code> or <code class="literal">+</code>, it behaves greedy, that is
the repeating operator will match as much characters as it can
but it will back off character by character during backtracking,
if that would allow to complete the rest of the match.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">On regex search</h3><p>There are some known issues with the
<code class="literal">java.util.regex</code> library, as it stands in
Java. In particular, it is possible to create
regular expressions that hang the JVM, or cause stack overflow
errors, which was not as easy to accomplish using the legacy
<code class="literal">gnu.regexp</code> library. If you find that
<code class="literal">gnu.regexp</code>, used in jEdit 4.2 and earlier, is
more suitable for your search/replace needs, you can try the
<span class="bold"><strong>XSearch plugin</strong></span>, which still
uses it and can provide a replacement to the built-in search
dialog.</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="globs.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="using-jedit-part.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="macro-index.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Appendix D. Glob Patterns </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Appendix F. Macros Included With jEdit</td></tr></table></div></body></html>
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