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  1. <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Appendix E. Regular Expressions</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2"><link rel="start" href="index.html" title="jEdit 4.3 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" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="regexps"></a>Appendix E. Regular Expressions</h2></div></div></div><p>jEdit 4.3pre5 and later uses regular expressions from <a class="ulink" href="http://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.html" target="_top">java.util.regex.Pattern</a>
    2. 

  2.     to implement inexact search and replace. Click there to see a complete
    3. 

  3.     reference guide to all supported meta-characters.</p><p>A regular expression consists of a string where some characters are
    4. 

  4.     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
    5. 

  5.         you escape XML special characters, such as &amp;, &lt;, &gt;, etc. You
    6. 

  6.         can use the XML plugin's "characters to entities" to perform this
    7. 

  7.         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
    8. 

  8.         by the regular expression engine, so you must make sure that backslashes
    9. 

  9.         are escaped by an extra backslash (<code class="literal">\\</code>)</p></div><p>Within a regular expression, the following characters have special
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  10.     meaning:</p><h4><a name="id2579273"></a>Positional Operators</h4><div class="itemizedlist"><ul type="disc"><li><p><code class="literal">^</code> matches at the beginning of a line</p></li><li><p><code class="literal">$</code> matches at the end of a line</p></li><li><p><code class="literal">\B</code> matches at a non-word break</p></li><li><p><code class="literal">\b</code> matches at a word boundary</p></li></ul></div><h4><a name="id2579327"></a>One-Character Operators</h4><div class="itemizedlist"><ul type="disc"><li><p><code class="literal">.</code> matches any single character</p></li><li><p><code class="literal">\d</code> matches any decimal digit</p></li><li><p><code class="literal">\D</code> matches any non-digit</p></li><li><p><code class="literal">\n</code> matches the newline character</p></li><li><p><code class="literal">\s</code> matches any whitespace character</p></li><li><p><code class="literal">\S</code> matches any non-whitespace
    11. 

  11.             character</p></li><li><p><code class="literal">\t</code> matches a horizontal tab
    12. 

  12.             character</p></li><li><p><code class="literal">\w</code> matches any word (alphanumeric)
    13. 

  13.             character</p></li><li><p><code class="literal">\W</code> matches any non-word (alphanumeric)
    14. 

  14.             character</p></li><li><p><code class="literal">\\</code> matches the backslash (&#8220;<span class="quote">\</span>&#8221;)
    15. 

  15.             character</p></li></ul></div><h4><a name="id2580272"></a>Character Class Operator</h4><div class="itemizedlist"><ul type="disc"><li><p><code class="literal">[<em class="replaceable"><code>abc</code></em>]</code> matches
    16. 

  16.             any character in the set <em class="replaceable"><code>a</code></em>,
    17. 

  17.             <em class="replaceable"><code>b</code></em> or <em class="replaceable"><code>c</code></em></p></li><li><p><code class="literal">[^<em class="replaceable"><code>abc</code></em>]</code> matches
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  18.             any character not in the set <em class="replaceable"><code>a</code></em>,
    19. 

  19.             <em class="replaceable"><code>b</code></em> or <em class="replaceable"><code>c</code></em></p></li><li><p><code class="literal">[<em class="replaceable"><code>a-z</code></em>]</code> matches
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  20.             any character in the range <em class="replaceable"><code>a</code></em> to
    21. 

  21.             <em class="replaceable"><code>z</code></em>, inclusive. A leading or trailing dash
    22. 

  22.             will be interpreted literally</p></li></ul></div><h4><a name="id2580352"></a>Subexpressions and Backreferences</h4><div class="itemizedlist"><ul type="disc"><li><p><code class="literal">(<em class="replaceable"><code>abc</code></em>)</code> matches
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  23.             whatever the expression <em class="replaceable"><code>abc</code></em> would match,
    24. 

  24.             and saves it as a subexpression. Also used for grouping</p></li><li><p><code class="literal">(?:<em class="replaceable"><code>...</code></em>)</code> pure
    25. 

  25.             grouping operator, does not save contents</p></li><li><p><code class="literal">(?#<em class="replaceable"><code>...</code></em>)</code> embedded
    26. 

  26.             comment, ignored by engine</p></li><li><p><code class="literal">(?=<em class="replaceable"><code>...</code></em>)</code> positive
    27. 

  27.             lookahead; the regular expression will match if the text in the
    28. 

  28.             brackets matches, but that text will not be considered part of the
    29. 

  29.             match</p></li><li><p><code class="literal">(?!<em class="replaceable"><code>...</code></em>)</code> negative
    30. 

  30.             lookahead; the regular expression will match if the text in the
    31. 

  31.             brackets does not match, and that text will not be considered part
    32. 

  32.             of the match</p></li><li><p><code class="literal">\<em class="replaceable"><code>n</code></em></code> where 0 &lt;
    33. 

  33.             <em class="replaceable"><code>n</code></em> &lt; 10, matches the same thing the
    34. 

  34.             <em class="replaceable"><code>n</code></em>th subexpression matched. Can only be
    35. 

  35.             used in the search string</p></li><li><p><code class="literal">$<em class="replaceable"><code>n</code></em></code> where 0 &lt;
    36. 

  36.             <em class="replaceable"><code>n</code></em> &lt; 10, substituted with the text
    37. 

  37.             matched by the <em class="replaceable"><code>n</code></em>th subexpression. Can
    38. 

  38.             only be used in the replacement string</p></li></ul></div><h4><a name="id2580494"></a>Branching (Alternation) Operator</h4><div class="itemizedlist"><ul type="disc"><li><p><code class="literal"><em class="replaceable"><code>a</code></em>|<em class="replaceable"><code>b</code></em></code>
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  39.             matches whatever the expression <em class="replaceable"><code>a</code></em> would
    40. 

  40.             match, or whatever the expression <em class="replaceable"><code>b</code></em> would
    41. 

  41.             match.</p></li></ul></div><h4><a name="id2580527"></a>Repeating Operators</h4><p>These symbols operate on the previous atomic expression.</p><div class="itemizedlist"><ul type="disc"><li><p><code class="literal">?</code> matches the preceding expression or the
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  42.             null string</p></li><li><p><code class="literal">*</code> matches the null string or any number of
    43. 

  43.             repetitions of the preceding expression</p></li><li><p><code class="literal">+</code> matches one or more repetitions of the
    44. 

  44.             preceding expression</p></li><li><p><code class="literal">{<em class="replaceable"><code>m</code></em>}</code> matches
    45. 

  45.             exactly <em class="replaceable"><code>m</code></em> repetitions of the
    46. 

  46.             one-character expression</p></li><li><p><code class="literal">{<em class="replaceable"><code>m</code></em>,<em class="replaceable"><code>n</code></em>}</code>
    47. 

  47.             matches between <em class="replaceable"><code>m</code></em> and
    48. 

  48.             <em class="replaceable"><code>n</code></em> repetitions of the preceding
    49. 

  49.             expression, inclusive</p></li><li><p><code class="literal">{<em class="replaceable"><code>m</code></em>,}</code> matches
    50. 

  50.             <em class="replaceable"><code>m</code></em> or more repetitions of the preceding
    51. 

  51.             expression</p></li></ul></div><h4><a name="id2580641"></a>Stingy (Minimal) Matching</h4><p>If a repeating operator (above) is immediately followed by a
    52. 

  52.     <code class="literal">?</code>, the repeating operator will stop at the smallest
    53. 

  53.     number of repetitions that can 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
    54. 

  54.                 <code class="literal">java.util.regex</code> library, as it stands in
    55. 

  55.                 Sun's Java 1.5 and 1.6. In particular, it is possible to create
    56. 

  56.                 regular expressions that hang the JVM, or cause stack overflow
    57. 

  57.                 errors, which was not as easy to accomplish using the legacy
    58. 

  58.                 <code class="literal">gnu.regexp</code> library. If you find that
    59. 

  59.                 <code class="literal">gnu.regexp</code>, used in jEdit 4.2 and earlier, is
    60. 

  60.                 more suitable for your search/replace needs, you can try the
    61. 

  61.                 <span class="bold"><strong>XSearch plugin</strong></span>, which still
    62. 

  62.                 uses it and can provide a replacement to the built-in search
    63. 

  63.                 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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