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| author | Leo Tenenbaum <pommicket@gmail.com> | 2018-08-20 21:12:06 -0400 |
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| committer | Leo Tenenbaum <pommicket@gmail.com> | 2018-08-20 21:12:06 -0400 |
| commit | 63e87c2d0c9d263f14c77b68f85c67d46ece82a9 (patch) | |
| tree | 6260365cbf7d24f37d27669e8538227fcb72e243 /gtk+-mingw/share/gtk-doc/html/glib/glib-regex-syntax.html | |
| parent | a4460f6d9453bbd7e584937686449cef3e19f052 (diff) | |
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diff --git a/gtk+-mingw/share/gtk-doc/html/glib/glib-regex-syntax.html b/gtk+-mingw/share/gtk-doc/html/glib/glib-regex-syntax.html deleted file mode 100644 index d7f28cf..0000000 --- a/gtk+-mingw/share/gtk-doc/html/glib/glib-regex-syntax.html +++ /dev/null @@ -1,2217 +0,0 @@ -<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> -<html> -<head> -<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> -<title>Regular expression syntax</title> -<meta name="generator" content="DocBook XSL Stylesheets V1.76.1"> -<link rel="home" href="index.html" title="GLib Reference Manual"> -<link rel="up" href="glib-utilities.html" title="GLib Utilities"> -<link rel="prev" href="glib-Perl-compatible-regular-expressions.html" title="Perl-compatible regular expressions"> -<link rel="next" href="glib-Simple-XML-Subset-Parser.html" title="Simple XML Subset Parser"> -<meta name="generator" content="GTK-Doc V1.18 (XML mode)"> -<link rel="stylesheet" href="style.css" type="text/css"> -</head> -<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> -<table class="navigation" id="top" width="100%" summary="Navigation header" cellpadding="2" cellspacing="2"><tr valign="middle"> -<td><a accesskey="p" href="glib-Perl-compatible-regular-expressions.html"><img src="left.png" width="24" height="24" border="0" alt="Prev"></a></td> -<td><a accesskey="u" href="glib-utilities.html"><img src="up.png" width="24" height="24" border="0" alt="Up"></a></td> -<td><a accesskey="h" href="index.html"><img src="home.png" width="24" height="24" border="0" alt="Home"></a></td> -<th width="100%" align="center">GLib Reference Manual</th> -<td><a accesskey="n" href="glib-Simple-XML-Subset-Parser.html"><img src="right.png" width="24" height="24" border="0" alt="Next"></a></td> -</tr></table> -<div class="refentry"> -<a name="glib-regex-syntax"></a><div class="titlepage"></div> -<div class="refnamediv"><table width="100%"><tr> -<td valign="top"> -<h2><span class="refentrytitle">Regular expression syntax</span></h2> -<p>Regular expression syntax — -syntax and semantics of regular expressions supported by GRegex -</p> -</td> -<td valign="top" align="right"></td> -</tr></table></div> -<div class="refsect1"> -<a name="idp23526384"></a><h2>GRegex regular expression details</h2> -<p> -A regular expression is a pattern that is matched against a -string from left to right. Most characters stand for themselves in a -pattern, and match the corresponding characters in the string. As a -trivial example, the pattern -</p> -<pre class="programlisting"> -The quick brown fox -</pre> -<p> -matches a portion of a string that is identical to itself. When -caseless matching is specified (the <code class="varname">G_REGEX_CASELESS</code> flag), letters are -matched independently of case. -</p> -<p> -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 metacharacters, which do not stand for themselves -but instead are interpreted in some special way. -</p> -<p> -There are two different sets of metacharacters: those that are recognized -anywhere in the pattern except within square brackets, and those -that are recognized in square brackets. Outside square brackets, the -metacharacters are as follows: -</p> -<div class="table"> -<a name="idp25205184"></a><p class="title"><b>Table 1. Metacharacters outside square brackets</b></p> -<div class="table-contents"><table summary="Metacharacters outside square brackets" border="1"> -<colgroup> -<col align="center"> -<col> -</colgroup> -<thead><tr> -<th align="center">Character</th> -<th>Meaning</th> -</tr></thead> -<tbody> -<tr> -<td align="center">\</td> -<td>general escape character with several uses</td> -</tr> -<tr> -<td align="center">^</td> -<td>assert start of string (or line, in multiline mode)</td> -</tr> -<tr> -<td align="center">$</td> -<td>assert end of string (or line, in multiline mode)</td> -</tr> -<tr> -<td align="center">.</td> -<td>match any character except newline (by default)</td> -</tr> -<tr> -<td align="center">[</td> -<td>start character class definition</td> -</tr> -<tr> -<td align="center">|</td> -<td>start of alternative branch</td> -</tr> -<tr> -<td align="center">(</td> -<td>start subpattern</td> -</tr> -<tr> -<td align="center">)</td> -<td>end subpattern</td> -</tr> -<tr> -<td align="center">?</td> -<td>extends the meaning of (, or 0/1 quantifier, or quantifier minimizer</td> -</tr> -<tr> -<td align="center">*</td> -<td>0 or more quantifier</td> -</tr> -<tr> -<td align="center">+</td> -<td>1 or more quantifier, also "possessive quantifier"</td> -</tr> -<tr> -<td align="center">{</td> -<td>start min/max quantifier</td> -</tr> -</tbody> -</table></div> -</div> -<br class="table-break"><p> -Part of a pattern that is in square brackets is called a "character -class". In a character class the only metacharacters are: -</p> -<div class="table"> -<a name="idp35969120"></a><p class="title"><b>Table 2. Metacharacters inside square brackets</b></p> -<div class="table-contents"><table summary="Metacharacters inside square brackets" border="1"> -<colgroup> -<col align="center"> -<col> -</colgroup> -<thead><tr> -<th align="center">Character</th> -<th>Meaning</th> -</tr></thead> -<tbody> -<tr> -<td align="center">\</td> -<td>general escape character</td> -</tr> -<tr> -<td align="center">^</td> -<td>negate the class, but only if the first character</td> -</tr> -<tr> -<td align="center">-</td> -<td>indicates character range</td> -</tr> -<tr> -<td align="center">[</td> -<td>POSIX character class (only if followed by POSIX syntax)</td> -</tr> -<tr> -<td align="center">]</td> -<td>terminates the character class</td> -</tr> -</tbody> -</table></div> -</div> -<br class="table-break"> -</div> -<div class="refsect1"> -<a name="idp35981504"></a><h2>Backslash</h2> -<p> -The backslash character has several uses. Firstly, if it is followed by -a non-alphanumeric character, it takes away any special meaning that -character may have. This use of backslash as an escape character -applies both inside and outside character classes. -</p> -<p> -For example, if you want to match a * character, you write \* in the -pattern. This escaping action applies whether or not the following -character would otherwise be interpreted as a metacharacter, so it is -always safe to precede a non-alphanumeric with backslash to specify -that it stands for itself. In particular, if you want to match a -backslash, you write \\. -</p> -<p> -If a pattern is compiled with the <code class="varname">G_REGEX_EXTENDED</code> -option, whitespace in the pattern (other than in a character class) and -characters between a # outside a character class and the next newline -are ignored. -An escaping backslash can be used to include a whitespace or # character -as part of the pattern. -</p> -<p> -Note that the C compiler interprets backslash in strings itself, therefore -you need to duplicate all \ characters when you put a regular expression -in a C string, like "\\d{3}". -</p> -<p> -If you want to remove the special meaning from a sequence of characters, -you can do so by putting them between \Q and \E. -The \Q...\E sequence is recognized both inside and outside character -classes. -</p> -<div class="refsect2"> -<a name="idp37458544"></a><h3>Non-printing characters</h3> -<p> -A second use of backslash provides a way of encoding non-printing -characters in patterns in a visible manner. There is no restriction on the -appearance of non-printing characters, apart from the binary zero that -terminates a pattern, but when a pattern is being prepared by text -editing, it is usually easier to use one of the following escape -sequences than the binary character it represents: -</p> -<div class="table"> -<a name="idp37460112"></a><p class="title"><b>Table 3. Non-printing characters</b></p> -<div class="table-contents"><table summary="Non-printing characters" border="1"> -<colgroup> -<col align="center"> -<col> -</colgroup> -<thead><tr> -<th align="center">Escape</th> -<th>Meaning</th> -</tr></thead> -<tbody> -<tr> -<td align="center">\a</td> -<td>alarm, that is, the BEL character (hex 07)</td> -</tr> -<tr> -<td align="center">\cx</td> -<td>"control-x", where x is any character</td> -</tr> -<tr> -<td align="center">\e</td> -<td>escape (hex 1B)</td> -</tr> -<tr> -<td align="center">\f</td> -<td>formfeed (hex 0C)</td> -</tr> -<tr> -<td align="center">\n</td> -<td>newline (hex 0A)</td> -</tr> -<tr> -<td align="center">\r</td> -<td>carriage return (hex 0D)</td> -</tr> -<tr> -<td align="center">\t</td> -<td>tab (hex 09)</td> -</tr> -<tr> -<td align="center">\ddd</td> -<td>character with octal code ddd, or backreference</td> -</tr> -<tr> -<td align="center">\xhh</td> -<td>character with hex code hh</td> -</tr> -<tr> -<td align="center">\x{hhh..}</td> -<td>character with hex code hhh..</td> -</tr> -</tbody> -</table></div> -</div> -<br class="table-break"><p> -The precise effect of \cx is as follows: if x is a lower case letter, -it is converted to upper case. Then bit 6 of the character (hex 40) is -inverted. Thus \cz becomes hex 1A, but \c{ becomes hex 3B, while \c; -becomes hex 7B. -</p> -<p> -After \x, from zero to two hexadecimal digits are read (letters can be -in upper or lower case). Any number of hexadecimal digits may appear -between \x{ and }, but the value of the character code -must be less than 2**31 (that is, the maximum hexadecimal value is -7FFFFFFF). If characters other than hexadecimal digits appear between -\x{ and }, or if there is no terminating }, this form of escape is not -recognized. Instead, the initial \x will be interpreted as a basic hexadecimal -escape, with no following digits, giving a character whose -value is zero. -</p> -<p> -Characters whose value is less than 256 can be defined by either of the -two syntaxes for \x. There is no difference -in the way they are handled. For example, \xdc is exactly the same as -\x{dc}. -</p> -<p> -After \0 up to two further octal digits are read. If there are fewer -than two digits, just those that are present are used. -Thus the sequence \0\x\07 specifies two binary zeros followed by a BEL -character (code value 7). Make sure you supply two digits after the -initial zero if the pattern character that follows is itself an octal -digit. -</p> -<p> -The handling of a backslash followed by a digit other than 0 is complicated. -Outside a character class, GRegex reads it and any following digits as a -decimal number. If the number is less than 10, or if there -have been at least that many previous capturing left parentheses in the -expression, the entire sequence is taken as a back reference. A -description of how this works is given later, following the discussion -of parenthesized subpatterns. -</p> -<p> -Inside a character class, or if the decimal number is greater than 9 -and there have not been that many capturing subpatterns, GRegex re-reads -up to three octal digits following the backslash, and uses them to generate -a data character. Any subsequent digits stand for themselves. For example: -</p> -<div class="table"> -<a name="idp37483696"></a><p class="title"><b>Table 4. Non-printing characters</b></p> -<div class="table-contents"><table summary="Non-printing characters" border="1"> -<colgroup> -<col align="center"> -<col> -</colgroup> -<thead><tr> -<th align="center">Escape</th> -<th>Meaning</th> -</tr></thead> -<tbody> -<tr> -<td align="center">\040</td> -<td>is another way of writing a space</td> -</tr> -<tr> -<td align="center">\40</td> -<td>is the same, provided there are fewer than 40 previous capturing subpatterns</td> -</tr> -<tr> -<td align="center">\7</td> -<td>is always a back reference</td> -</tr> -<tr> -<td align="center">\11</td> -<td>might be a back reference, or another way of writing a tab</td> -</tr> -<tr> -<td align="center">\011</td> -<td>is always a tab</td> -</tr> -<tr> -<td align="center">\0113</td> -<td>is a tab followed by the character "3"</td> -</tr> -<tr> -<td align="center">\113</td> -<td>might be a back reference, otherwise the character with octal code 113</td> -</tr> -<tr> -<td align="center">\377</td> -<td>might be a back reference, otherwise the byte consisting entirely of 1 bits</td> -</tr> -<tr> -<td align="center">\81</td> -<td>is either a back reference, or a binary zero followed by the two characters "8" and "1"</td> -</tr> -</tbody> -</table></div> -</div> -<br class="table-break"><p> -Note that octal values of 100 or greater must not be introduced by a -leading zero, because no more than three octal digits are ever read. -</p> -<p> -All the sequences that define a single character can be used both inside -and outside character classes. In addition, inside a character class, the -sequence \b is interpreted as the backspace character (hex 08), and the -sequences \R and \X are interpreted as the characters "R" and "X", respectively. -Outside a character class, these sequences have different meanings (see below). -</p> -</div> -<hr> -<div class="refsect2"> -<a name="idp37502736"></a><h3>Absolute and relative back references</h3> -<p> -The sequence \g followed by a positive or negative number, optionally enclosed -in braces, is an absolute or relative back reference. Back references are -discussed later, following the discussion of parenthesized subpatterns. -</p> -</div> -<hr> -<div class="refsect2"> -<a name="idp37504304"></a><h3>Generic character types</h3> -<p> -Another use of backslash is for specifying generic character types. -The following are always recognized: -</p> -<div class="table"> -<a name="idp37505584"></a><p class="title"><b>Table 5. Generic characters</b></p> -<div class="table-contents"><table summary="Generic characters" border="1"> -<colgroup> -<col align="center"> -<col> -</colgroup> -<thead><tr> -<th align="center">Escape</th> -<th>Meaning</th> -</tr></thead> -<tbody> -<tr> -<td align="center">\d</td> -<td>any decimal digit</td> -</tr> -<tr> -<td align="center">\D</td> -<td>any character that is not a decimal digit</td> -</tr> -<tr> -<td align="center">\s</td> -<td>any whitespace character</td> -</tr> -<tr> -<td align="center">\S</td> -<td>any character that is not a whitespace character</td> -</tr> -<tr> -<td align="center">\w</td> -<td>any "word" character</td> -</tr> -<tr> -<td align="center">\W</td> -<td>any "non-word" character</td> -</tr> -</tbody> -</table></div> -</div> -<br class="table-break"><p> -Each pair of escape sequences partitions the complete set of characters -into two disjoint sets. Any given character matches one, and only one, -of each pair. -</p> -<p> -These character type sequences can appear both inside and outside character -classes. They each match one character of the appropriate type. -If the current matching point is at the end of the passed string, all -of them fail, since there is no character to match. -</p> -<p> -For compatibility with Perl, \s does not match the VT character (code -11). This makes it different from the the POSIX "space" class. The \s -characters are HT (9), LF (10), FF (12), CR (13), and space (32). -</p> -<p> -A "word" character is an underscore or any character less than 256 that -is a letter or digit.</p> -<p> -Characters with values greater than 128 never match \d, -\s, or \w, and always match \D, \S, and \W. -</p> -</div> -<hr> -<div class="refsect2"> -<a name="idp37522256"></a><h3>Newline sequences</h3> -<p>Outside a character class, the escape sequence \R matches any Unicode -newline sequence. -This particular group matches either the two-character sequence CR followed by -LF, or one of the single characters LF (linefeed, U+000A), VT (vertical tab, -U+000B), FF (formfeed, U+000C), CR (carriage return, U+000D), NEL (next -line, U+0085), LS (line separator, U+2028), or PS (paragraph separator, U+2029). -The two-character sequence is treated as a single unit that -cannot be split. Inside a character class, \R matches the letter "R".</p> -</div> -<hr> -<div class="refsect2"> -<a name="idp37524112"></a><h3>Unicode character properties</h3> -<p> -To support generic character types there are three additional escape -sequences, they are: -</p> -<div class="table"> -<a name="idp37525392"></a><p class="title"><b>Table 6. Generic character types</b></p> -<div class="table-contents"><table summary="Generic character types" border="1"> -<colgroup> -<col align="center"> -<col> -</colgroup> -<thead><tr> -<th align="center">Escape</th> -<th>Meaning</th> -</tr></thead> -<tbody> -<tr> -<td align="center">\p{xx}</td> -<td>a character with the xx property</td> -</tr> -<tr> -<td align="center">\P{xx}</td> -<td>a character without the xx property</td> -</tr> -<tr> -<td align="center">\X</td> -<td>an extended Unicode sequence</td> -</tr> -</tbody> -</table></div> -</div> -<br class="table-break"><p> -The property names represented by xx above are limited to the Unicode -script names, the general category properties, and "Any", which matches -any character (including newline). Other properties such as "InMusicalSymbols" -are not currently supported. Note that \P{Any} does not match any characters, -so always causes a match failure. -</p> -<p> -Sets of Unicode characters are defined as belonging to certain scripts. A -character from one of these sets can be matched using a script name. For -example, \p{Greek} or \P{Han}. -</p> -<p> -Those that are not part of an identified script are lumped together as -"Common". The current list of scripts can be found in the documentation for -the #GUnicodeScript enumeration. Script names for use with \p{} can be -found by replacing all spaces with underscores, e.g. for Linear B use -\p{Linear_B}. -</p> -<p> -Each character has exactly one general category property, specified by a -two-letter abbreviation. For compatibility with Perl, negation can be specified -by including a circumflex between the opening brace and the property name. For -example, \p{^Lu} is the same as \P{Lu}. -</p> -<p> -If only one letter is specified with \p or \P, it includes all the general -category properties that start with that letter. In this case, in the absence -of negation, the curly brackets in the escape sequence are optional; these two -examples have the same effect: -</p> -<pre class="programlisting"> -\p{L} -\pL -</pre> -<p> -In addition to the two-letter category codes listed in the -documentation for the #GUnicodeType enumeration, the following -general category property codes are supported: -</p> -<div class="table"> -<a name="idp37539824"></a><p class="title"><b>Table 7. Property codes</b></p> -<div class="table-contents"><table summary="Property codes" border="1"> -<colgroup> -<col align="center"> -<col> -</colgroup> -<thead><tr> -<th align="center">Code</th> -<th>Meaning</th> -</tr></thead> -<tbody> -<tr> -<td align="center">C</td> -<td>Other</td> -</tr> -<tr> -<td align="center">L</td> -<td>Letter</td> -</tr> -<tr> -<td align="center">M</td> -<td>Mark</td> -</tr> -<tr> -<td align="center">N</td> -<td>Number</td> -</tr> -<tr> -<td align="center">P</td> -<td>Punctuation</td> -</tr> -<tr> -<td align="center">S</td> -<td>Symbol</td> -</tr> -<tr> -<td align="center">Z</td> -<td>Separator</td> -</tr> -</tbody> -</table></div> -</div> -<br class="table-break"><p> -The special property L& is also supported: it matches a character that has -the Lu, Ll, or Lt property, in other words, a letter that is not classified as -a modifier or "other". -</p> -<p> -The long synonyms for these properties that Perl supports (such as \ep{Letter}) -are not supported by GRegex, nor is it permitted to prefix any of these -properties with "Is". -</p> -<p> -No character that is in the Unicode table has the Cn (unassigned) property. -Instead, this property is assumed for any code point that is not in the -Unicode table. -</p> -<p> -Specifying caseless matching does not affect these escape sequences. -For example, \p{Lu} always matches only upper case letters. -</p> -<p> -The \X escape matches any number of Unicode characters that form an -extended Unicode sequence. \X is equivalent to -</p> -<pre class="programlisting"> -(?>\PM\pM*) -</pre> -<p> -That is, it matches a character without the "mark" property, followed -by zero or more characters with the "mark" property, and treats the -sequence as an atomic group (see below). Characters with the "mark" -property are typically accents that affect the preceding character. -</p> -<p> -Matching characters by Unicode property is not fast, because GRegex has -to search a structure that contains data for over fifteen thousand -characters. That is why the traditional escape sequences such as \d and -\w do not use Unicode properties. -</p> -</div> -<hr> -<div class="refsect2"> -<a name="idp41263504"></a><h3>Simple assertions</h3> -<p> -The final use of backslash is for certain simple assertions. An -assertion specifies a condition that has to be met at a particular point in -a match, without consuming any characters from the string. The -use of subpatterns for more complicated assertions is described below. -The backslashed assertions are: -</p> -<div class="table"> -<a name="idp41264976"></a><p class="title"><b>Table 8. Simple assertions</b></p> -<div class="table-contents"><table summary="Simple assertions" border="1"> -<colgroup> -<col align="center"> -<col> -</colgroup> -<thead><tr> -<th align="center">Escape</th> -<th>Meaning</th> -</tr></thead> -<tbody> -<tr> -<td align="center">\b</td> -<td>matches at a word boundary</td> -</tr> -<tr> -<td align="center">\B</td> -<td>matches when not at a word boundary</td> -</tr> -<tr> -<td align="center">\A</td> -<td>matches at the start of the string</td> -</tr> -<tr> -<td align="center">\Z</td> -<td>matches at the end of the string or before a newline at the end of the string</td> -</tr> -<tr> -<td align="center">\z</td> -<td>matches only at the end of the string</td> -</tr> -<tr> -<td align="center">\G</td> -<td>matches at first matching position in the string</td> -</tr> -</tbody> -</table></div> -</div> -<br class="table-break"><p> -These assertions may not appear in character classes (but note that \b -has a different meaning, namely the backspace character, inside a -character class). -</p> -<p> -A word boundary is a position in the string where the current -character and the previous character do not both match \w or \W (i.e. -one matches \w and the other matches \W), or the start or end of the -string if the first or last character matches \w, respectively. -</p> -<p> -The \A, \Z, and \z assertions differ from the traditional circumflex -and dollar (described in the next section) in that they only ever match -at the very start and end of the string, whatever options are -set. Thus, they are independent of multiline mode. These three assertions -are not affected by the <code class="varname">G_REGEX_MATCH_NOTBOL</code> or <code class="varname">G_REGEX_MATCH_NOTEOL</code> options, -which affect only the behaviour of the circumflex and dollar metacharacters. -However, if the start_position argument of a matching function is non-zero, -indicating that matching is to start at a point other than the beginning of -the string, \A can never match. The difference between \Z and \z is -that \Z matches before a newline at the end of the string as well at the -very end, whereas \z matches only at the end. -</p> -<p> -The \G assertion is true only when the current matching position is at -the start point of the match, as specified by the start_position argument -to the matching functions. It differs from \A when the value of startoffset is -non-zero. -</p> -<p> -Note, however, that the interpretation of \G, as the start of the -current match, is subtly different from Perl’s, which defines it as the -end of the previous match. In Perl, these can be different when the -previously matched string was empty. -</p> -<p> -If all the alternatives of a pattern begin with \G, the expression is -anchored to the starting match position, and the "anchored" flag is set -in the compiled regular expression. -</p> -</div> -</div> -<div class="refsect1"> -<a name="idp41284160"></a><h2>Circumflex and dollar</h2> -<p> -Outside a character class, in the default matching mode, the circumflex -character is an assertion that is true only if the current matching -point is at the start of the string. If the start_position argument to -the matching functions is non-zero, circumflex can never match if the -<code class="varname">G_REGEX_MULTILINE</code> option is unset. Inside a character class, circumflex -has an entirely different meaning (see below). -</p> -<p> -Circumflex need not be the first character of the pattern if a number -of alternatives are involved, but it should be the first thing in each -alternative in which it appears if the pattern is ever to match that -branch. If all possible alternatives start with a circumflex, that is, -if the pattern is constrained to match only at the start of the string, -it is said to be an "anchored" pattern. (There are also other -constructs that can cause a pattern to be anchored.) -</p> -<p> -A dollar character is an assertion that is true only if the current -matching point is at the end of the string, or immediately -before a newline at the end of the string (by default). Dollar need not -be the last character of the pattern if a number of alternatives are -involved, but it should be the last item in any branch in which it -appears. Dollar has no special meaning in a character class. -</p> -<p> -The meaning of dollar can be changed so that it matches only at the -very end of the string, by setting the <code class="varname">G_REGEX_DOLLAR_ENDONLY</code> option at -compile time. This does not affect the \Z assertion. -</p> -<p> -The meanings of the circumflex and dollar characters are changed if the -<code class="varname">G_REGEX_MULTILINE</code> option is set. When this is the case, -a circumflex matches immediately after internal newlines as well as at the -start of the string. It does not match after a newline that ends the string. -A dollar matches before any newlines in the string, as well as at the very -end, when <code class="varname">G_REGEX_MULTILINE</code> is set. When newline is -specified as the two-character sequence CRLF, isolated CR and LF characters -do not indicate newlines. -</p> -<p> -For example, the pattern /^abc$/ matches the string "def\nabc" (where -\n represents a newline) in multiline mode, but not otherwise. Consequently, -patterns that are anchored in single line mode because all branches start with -^ are not anchored in multiline mode, and a match for circumflex is possible -when the <code class="varname">start_position</code> argument of a matching function -is non-zero. The <code class="varname">G_REGEX_DOLLAR_ENDONLY</code> option is ignored -if <code class="varname">G_REGEX_MULTILINE</code> is set. -</p> -<p> -Note that the sequences \A, \Z, and \z can be used to match the start and -end of the string in both modes, and if all branches of a pattern start with -\A it is always anchored, whether or not <code class="varname">G_REGEX_MULTILINE</code> -is set. -</p> -</div> -<div class="refsect1"> -<a name="idp41293808"></a><h2>Full stop (period, dot)</h2> -<p> -Outside a character class, a dot in the pattern matches any one character -in the string, including a non-printing character, but not (by -default) newline. In UTF-8 a character might be more than one byte long. -</p> -<p> -When a line ending is defined as a single character, dot never matches that -character; when the two-character sequence CRLF is used, dot does not match CR -if it is immediately followed by LF, but otherwise it matches all characters -(including isolated CRs and LFs). When any Unicode line endings are being -recognized, dot does not match CR or LF or any of the other line ending -characters. -</p> -<p> -If the <code class="varname">G_REGEX_DOTALL</code> flag is set, dots match newlines -as well. The handling of dot is entirely independent of the handling of circumflex -and dollar, the only relationship being that they both involve newline -characters. Dot has no special meaning in a character class. -</p> -<p> -The behaviour of dot with regard to newlines can be changed. If the -<code class="varname">G_REGEX_DOTALL</code> option is set, a dot matches any one -character, without exception. If newline is defined as the two-character -sequence CRLF, it takes two dots to match it. -</p> -<p> -The handling of dot is entirely independent of the handling of circumflex and -dollar, the only relationship being that they both involve newlines. Dot has no -special meaning in a character class. -</p> -</div> -<div class="refsect1"> -<a name="idp41298928"></a><h2>Matching a single byte</h2> -<p> -Outside a character class, the escape sequence \C matches any one byte, -both in and out of UTF-8 mode. Unlike a dot, it always matches any line -ending characters. -The feature is provided in Perl in order to match individual bytes in -UTF-8 mode. Because it breaks up UTF-8 characters into individual -bytes, what remains in the string may be a malformed UTF-8 string. For -this reason, the \C escape sequence is best avoided. -</p> -<p> -GRegex does not allow \C to appear in lookbehind assertions (described -below), because in UTF-8 mode this would make it impossible to calculate -the length of the lookbehind. -</p> -</div> -<div class="refsect1"> -<a name="idp41301296"></a><h2>Square brackets and character classes</h2> -<p> -An opening square bracket introduces a character class, terminated by a -closing square bracket. A closing square bracket on its own is not special. If a closing square bracket is required as a member of the class, -it should be the first data character in the class (after an initial -circumflex, if present) or escaped with a backslash. -</p> -<p> -A character class matches a single character in the string. A matched character -must be in the set of characters defined by the class, unless the first -character in the class definition is a circumflex, in which case the -string character must not be in the set defined by the class. If a -circumflex is actually required as a member of the class, ensure it is -not the first character, or escape it with a backslash. -</p> -<p> -For example, the character class [aeiou] matches any lower case vowel, -while [^aeiou] matches any character that is not a lower case vowel. -Note that a circumflex is just a convenient notation for specifying the -characters that are in the class by enumerating those that are not. A -class that starts with a circumflex is not an assertion: it still consumes -a character from the string, and therefore it fails if the current pointer -is at the end of the string. -</p> -<p> -In UTF-8 mode, characters with values greater than 255 can be included -in a class as a literal string of bytes, or by using the \x{ escaping -mechanism. -</p> -<p> -When caseless matching is set, any letters in a class represent both -their upper case and lower case versions, so for example, a caseless -[aeiou] matches "A" as well as "a", and a caseless [^aeiou] does not -match "A", whereas a caseful version would. -</p> -<p> -Characters that might indicate line breaks are never treated -in any special way when matching character classes, whatever line-ending -sequence is in use, and whatever setting of the <code class="varname">G_REGEX_DOTALL</code> -and <code class="varname">G_REGEX_MULTILINE</code> options is used. A class such as [^a] -always matches one of these characters. -</p> -<p> -The minus (hyphen) character can be used to specify a range of characters in -a character class. For example, [d-m] matches any letter -between d and m, inclusive. If a minus character is required in a -class, it must be escaped with a backslash or appear in a position -where it cannot be interpreted as indicating a range, typically as the -first or last character in the class. -</p> -<p> -It is not possible to have the literal character "]" as the end character -of a range. A pattern such as [W-]46] is interpreted as a class of -two characters ("W" and "-") followed by a literal string "46]", so it -would match "W46]" or "-46]". However, if the "]" is escaped with a -backslash it is interpreted as the end of range, so [W-\]46] is interpreted -as a class containing a range followed by two other characters. -The octal or hexadecimal representation of "]" can also be used to end -a range. -</p> -<p> -Ranges operate in the collating sequence of character values. They can -also be used for characters specified numerically, for example -[\000-\037]. In UTF-8 mode, ranges can include characters whose values -are greater than 255, for example [\x{100}-\x{2ff}]. -</p> -<p> -The character types \d, \D, \p, \P, \s, \S, \w, and \W may also appear -in a character class, and add the characters that they match to the -class. For example, [\dABCDEF] matches any hexadecimal digit. A -circumflex can conveniently be used with the upper case character types to -specify a more restricted set of characters than the matching lower -case type. For example, the class [^\W_] matches any letter or digit, -but not underscore. -</p> -<p> -The only metacharacters that are recognized in character classes are -backslash, hyphen (only where it can be interpreted as specifying a -range), circumflex (only at the start), opening square bracket (only -when it can be interpreted as introducing a POSIX class name - see the -next section), and the terminating closing square bracket. However, -escaping other non-alphanumeric characters does no harm. -</p> -</div> -<div class="refsect1"> -<a name="idp41311600"></a><h2>Posix character classes</h2> -<p> -GRegex supports the POSIX notation for character classes. This uses names -enclosed by [: and :] within the enclosing square brackets. For example, -</p> -<pre class="programlisting"> -[01[:alpha:]%] -</pre> -<p> -matches "0", "1", any alphabetic character, or "%". The supported class -names are -</p> -<div class="table"> -<a name="idp41313888"></a><p class="title"><b>Table 9. Posix classes</b></p> -<div class="table-contents"><table summary="Posix classes" border="1"> -<colgroup> -<col align="center"> -<col> -</colgroup> -<thead><tr> -<th align="center">Name</th> -<th>Meaning</th> -</tr></thead> -<tbody> -<tr> -<td align="center">alnum</td> -<td>letters and digits</td> -</tr> -<tr> -<td align="center">alpha</td> -<td>letters</td> -</tr> -<tr> -<td align="center">ascii</td> -<td>character codes 0 - 127</td> -</tr> -<tr> -<td align="center">blank</td> -<td>space or tab only</td> -</tr> -<tr> -<td align="center">cntrl</td> -<td>control characters</td> -</tr> -<tr> -<td align="center">digit</td> -<td>decimal digits (same as \d)</td> -</tr> -<tr> -<td align="center">graph</td> -<td>printing characters, excluding space</td> -</tr> -<tr> -<td align="center">lower</td> -<td>lower case letters</td> -</tr> -<tr> -<td align="center">print</td> -<td>printing characters, including space</td> -</tr> -<tr> -<td align="center">punct</td> -<td>printing characters, excluding letters and digits</td> -</tr> -<tr> -<td align="center">space</td> -<td>white space (not quite the same as \s)</td> -</tr> -<tr> -<td align="center">upper</td> -<td>upper case letters</td> -</tr> -<tr> -<td align="center">word</td> -<td>"word" characters (same as \w)</td> -</tr> -<tr> -<td align="center">xdigit</td> -<td>hexadecimal digits</td> -</tr> -</tbody> -</table></div> -</div> -<br class="table-break"><p> -The "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13), -and space (32). Notice that this list includes the VT character (code -11). This makes "space" different to \s, which does not include VT (for -Perl compatibility). -</p> -<p> -The name "word" is a Perl extension, and "blank" is a GNU extension. -Another Perl extension is negation, which is indicated by a ^ character -after the colon. For example, -</p> -<pre class="programlisting"> -[12[:^digit:]] -</pre> -<p> -matches "1", "2", or any non-digit. GRegex also recognize the -POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but -these are not supported, and an error is given if they are encountered. -</p> -<p> -In UTF-8 mode, characters with values greater than 128 do not match any -of the POSIX character classes. -</p> -</div> -<div class="refsect1"> -<a name="idp41341600"></a><h2>Vertical bar</h2> -<p> -Vertical bar characters are used to separate alternative patterns. For -example, the pattern -</p> -<pre class="programlisting"> - gilbert|sullivan -</pre> -<p> -matches either "gilbert" or "sullivan". Any number of alternatives may -appear, and an empty alternative is permitted (matching the empty -string). The matching process tries each alternative in turn, from -left to right, and the first one that succeeds is used. If the alternatives are within a subpattern (defined below), "succeeds" means matching the rest of the main pattern as well as the alternative in the subpattern. -</p> -</div> -<div class="refsect1"> -<a name="idp41344592"></a><h2>Internal option setting</h2> -<p> -The settings of the <code class="varname">G_REGEX_CASELESS</code>, <code class="varname">G_REGEX_MULTILINE</code>, <code class="varname">G_REGEX_MULTILINE</code>, -and <code class="varname">G_REGEX_EXTENDED</code> options can be changed from within the pattern by a -sequence of Perl-style option letters enclosed between "(?" and ")". The -option letters are -</p> -<div class="table"> -<a name="idp41347696"></a><p class="title"><b>Table 10. Option settings</b></p> -<div class="table-contents"><table summary="Option settings" border="1"> -<colgroup> -<col align="center"> -<col> -</colgroup> -<thead><tr> -<th align="center">Option</th> -<th>Flag</th> -</tr></thead> -<tbody> -<tr> -<td align="center">i</td> -<td><code class="varname">G_REGEX_CASELESS</code></td> -</tr> -<tr> -<td align="center">m</td> -<td><code class="varname">G_REGEX_MULTILINE</code></td> -</tr> -<tr> -<td align="center">s</td> -<td><code class="varname">G_REGEX_DOTALL</code></td> -</tr> -<tr> -<td align="center">x</td> -<td><code class="varname">G_REGEX_EXTENDED</code></td> -</tr> -</tbody> -</table></div> -</div> -<br class="table-break"><p> -For example, (?im) sets caseless, multiline matching. It is also -possible to unset these options by preceding the letter with a hyphen, and a -combined setting and unsetting such as (?im-sx), which sets <code class="varname">G_REGEX_CASELESS</code> -and <code class="varname">G_REGEX_MULTILINE</code> while unsetting <code class="varname">G_REGEX_DOTALL</code> and <code class="varname">G_REGEX_EXTENDED</code>, -is also permitted. If a letter appears both before and after the -hyphen, the option is unset. -</p> -<p> -When an option change occurs at top level (that is, not inside subpattern -parentheses), the change applies to the remainder of the pattern -that follows. -</p> -<p> -An option change within a subpattern (see below for a description of subpatterns) -affects only that part of the current pattern that follows it, so -</p> -<pre class="programlisting"> -(a(?i)b)c -</pre> -<p> -matches abc and aBc and no other strings (assuming <code class="varname">G_REGEX_CASELESS</code> is not -used). By this means, options can be made to have different settings -in different parts of the pattern. Any changes made in one alternative -do carry on into subsequent branches within the same subpattern. For -example, -</p> -<pre class="programlisting"> -(a(?i)b|c) -</pre> -<p> -matches "ab", "aB", "c", and "C", even though when matching "C" the -first branch is abandoned before the option setting. This is because -the effects of option settings happen at compile time. There would be -some very weird behaviour otherwise. -</p> -<p> -The options <code class="varname">G_REGEX_UNGREEDY</code> and -<code class="varname">G_REGEX_EXTRA</code> and <code class="varname">G_REGEX_DUPNAMES</code> -can be changed in the same way as the Perl-compatible options by using -the characters U, X and J respectively. -</p> -</div> -<div class="refsect1"> -<a name="idp41368000"></a><h2>Subpatterns</h2> -<p> -Subpatterns are delimited by parentheses (round brackets), which can be -nested. Turning part of a pattern into a subpattern does two things: -</p> -<div class="itemizedlist"><ul class="itemizedlist" type="disc"> -<li class="listitem"><p> -It localizes a set of alternatives. For example, the pattern -cat(aract|erpillar|) matches one of the words "cat", "cataract", or -"caterpillar". Without the parentheses, it would match "cataract", -"erpillar" or an empty string. -</p></li> -<li class="listitem"><p> -It sets up the subpattern as a capturing subpattern. This means -that, when the whole pattern matches, that portion of the -string that matched the subpattern can be obtained using <code class="function">g_match_info_fetch()</code>. -Opening parentheses are counted from left to right (starting from 1, as -subpattern 0 is the whole matched string) to obtain numbers for the -capturing subpatterns. -</p></li> -</ul></div> -<p> -For example, if the string "the red king" is matched against the pattern -</p> -<pre class="programlisting"> -the ((red|white) (king|queen)) -</pre> -<p> -the captured substrings are "red king", "red", and "king", and are numbered 1, 2, and 3, respectively. -</p> -<p> -The fact that plain parentheses fulfil two functions is not always -helpful. There are often times when a grouping subpattern is required -without a capturing requirement. If an opening parenthesis is followed -by a question mark and a colon, the subpattern does not do any capturing, -and is not counted when computing the number of any subsequent -capturing subpatterns. For example, if the string "the white queen" is -matched against the pattern -</p> -<pre class="programlisting"> -the ((?:red|white) (king|queen)) -</pre> -<p> -the captured substrings are "white queen" and "queen", and are numbered -1 and 2. The maximum number of capturing subpatterns is 65535. -</p> -<p> -As a convenient shorthand, if any option settings are required at the -start of a non-capturing subpattern, the option letters may appear -between the "?" and the ":". Thus the two patterns -</p> -<pre class="programlisting"> -(?i:saturday|sunday) -(?:(?i)saturday|sunday) -</pre> -<p> -match exactly the same set of strings. Because alternative branches are -tried from left to right, and options are not reset until the end of -the subpattern is reached, an option setting in one branch does affect -subsequent branches, so the above patterns match "SUNDAY" as well as -"Saturday". -</p> -</div> -<div class="refsect1"> -<a name="idp41378224"></a><h2>Named subpatterns</h2> -<p> -Identifying capturing parentheses by number is simple, but it can be -very hard to keep track of the numbers in complicated regular expressions. -Furthermore, if an expression is modified, the numbers may -change. To help with this difficulty, GRegex supports the naming of -subpatterns. A subpattern can be named in one of three ways: (?<name>...) or -(?'name'...) as in Perl, or (?P<name>...) as in Python. -References to capturing parentheses from other -parts of the pattern, such as backreferences, recursion, and conditions, -can be made by name as well as by number. -</p> -<p> -Names consist of up to 32 alphanumeric characters and underscores. Named -capturing parentheses are still allocated numbers as well as names, exactly as -if the names were not present. -By default, a name must be unique within a pattern, but it is possible to relax -this constraint by setting the <code class="varname">G_REGEX_DUPNAMES</code> option at -compile time. This can be useful for patterns where only one instance of the -named parentheses can match. Suppose you want to match the name of a weekday, -either as a 3-letter abbreviation or as the full name, and in both cases you -want to extract the abbreviation. This pattern (ignoring the line breaks) does -the job: -</p> -<pre class="programlisting"> -(?<DN>Mon|Fri|Sun)(?:day)?| -(?<DN>Tue)(?:sday)?| -(?<DN>Wed)(?:nesday)?| -(?<DN>Thu)(?:rsday)?| -(?<DN>Sat)(?:urday)? -</pre> -<p> -There are five capturing substrings, but only one is ever set after a match. -The function for extracting the data by name returns the substring -for the first (and in this example, the only) subpattern of that name that -matched. This saves searching to find which numbered subpattern it was. If you -make a reference to a non-unique named subpattern from elsewhere in the -pattern, the one that corresponds to the lowest number is used. -</p> -</div> -<div class="refsect1"> -<a name="idp41383296"></a><h2>Repetition</h2> -<p> -Repetition is specified by quantifiers, which can follow any of the -following items: -</p> -<div class="itemizedlist"><ul class="itemizedlist" type="disc"> -<li class="listitem"><p>a literal data character</p></li> -<li class="listitem"><p>the dot metacharacter</p></li> -<li class="listitem"><p>the \C escape sequence</p></li> -<li class="listitem"><p>the \X escape sequence (in UTF-8 mode)</p></li> -<li class="listitem"><p>the \R escape sequence</p></li> -<li class="listitem"><p>an escape such as \d that matches a single character</p></li> -<li class="listitem"><p>a character class</p></li> -<li class="listitem"><p>a back reference (see next section)</p></li> -<li class="listitem"><p>a parenthesized subpattern (unless it is an assertion)</p></li> -</ul></div> -<p> -The general repetition quantifier specifies a minimum and maximum number -of permitted matches, by giving the two numbers in curly brackets -(braces), separated by a comma. The numbers must be less than 65536, -and the first must be less than or equal to the second. For example: -</p> -<pre class="programlisting"> -z{2,4} -</pre> -<p> -matches "zz", "zzz", or "zzzz". A closing brace on its own is not a -special character. If the second number is omitted, but the comma is -present, there is no upper limit; if the second number and the comma -are both omitted, the quantifier specifies an exact number of required -matches. Thus -</p> -<pre class="programlisting"> -[aeiou]{3,} -</pre> -<p> -matches at least 3 successive vowels, but may match many more, while -</p> -<pre class="programlisting"> -\d{8} -</pre> -<p> -matches exactly 8 digits. An opening curly bracket that appears in a -position where a quantifier is not allowed, or one that does not match -the syntax of a quantifier, is taken as a literal character. For example, -{,6} is not a quantifier, but a literal string of four characters. -</p> -<p> -In UTF-8 mode, quantifiers apply to UTF-8 characters rather than to -individual bytes. Thus, for example, \x{100}{2} matches two UTF-8 -characters, each of which is represented by a two-byte sequence. Similarly, -\X{3} matches three Unicode extended sequences, each of which may be -several bytes long (and they may be of different lengths). -</p> -<p> -The quantifier {0} is permitted, causing the expression to behave as if -the previous item and the quantifier were not present. -</p> -<p> -For convenience, the three most common quantifiers have single-character -abbreviations: -</p> -<div class="table"> -<a name="idp41396640"></a><p class="title"><b>Table 11. Abbreviations for quantifiers</b></p> -<div class="table-contents"><table summary="Abbreviations for quantifiers" border="1"> -<colgroup> -<col align="center"> -<col> -</colgroup> -<thead><tr> -<th align="center">Abbreviation</th> -<th>Meaning</th> -</tr></thead> -<tbody> -<tr> -<td align="center">*</td> -<td>is equivalent to {0,}</td> -</tr> -<tr> -<td align="center">+</td> -<td>is equivalent to {1,}</td> -</tr> -<tr> -<td align="center">?</td> -<td>is equivalent to {0,1}</td> -</tr> -</tbody> -</table></div> -</div> -<br class="table-break"><p> -It is possible to construct infinite loops by following a subpattern -that can match no characters with a quantifier that has no upper limit, -for example: -</p> -<pre class="programlisting"> -(a?)* -</pre> -<p> -Because there are cases where this can be useful, such patterns are -accepted, but if any repetition of the subpattern does in fact match -no characters, the loop is forcibly broken. -</p> -<p> -By default, the quantifiers are "greedy", that is, they match as much -as possible (up to the maximum number of permitted times), without -causing the rest of the pattern to fail. The classic example of where -this gives problems is in trying to match comments in C programs. These -appear between /* and */ and within the comment, individual * and / -characters may appear. An attempt to match C comments by applying the -pattern -</p> -<pre class="programlisting"> -/\*.*\*/ -</pre> -<p> -to the string -</p> -<pre class="programlisting"> -/* first comment */ not comment /* second comment */ -</pre> -<p> -fails, because it matches the entire string owing to the greediness of -the .* item. -</p> -<p> -However, if a quantifier is followed by a question mark, it ceases to -be greedy, and instead matches the minimum number of times possible, so -the pattern -</p> -<pre class="programlisting"> -/\*.*?\*/ -</pre> -<p> -does the right thing with the C comments. The meaning of the various -quantifiers is not otherwise changed, just the preferred number of -matches. Do not confuse this use of question mark with its use as a -quantifier in its own right. Because it has two uses, it can sometimes -appear doubled, as in -</p> -<pre class="programlisting"> -\d??\d -</pre> -<p> -which matches one digit by preference, but can match two if that is the -only way the rest of the pattern matches. -</p> -<p> -If the <code class="varname">G_REGEX_UNGREEDY</code> flag is set, the quantifiers are not greedy -by default, but individual ones can be made greedy by following them with -a question mark. In other words, it inverts the default behaviour. -</p> -<p> -When a parenthesized subpattern is quantified with a minimum repeat -count that is greater than 1 or with a limited maximum, more memory is -required for the compiled pattern, in proportion to the size of the -minimum or maximum. -</p> -<p> -If a pattern starts with .* or .{0,} and the <code class="varname">G_REGEX_DOTALL</code> flag -is set, thus allowing the dot to match newlines, the -pattern is implicitly anchored, because whatever follows will be tried -against every character position in the string, so there is no -point in retrying the overall match at any position after the first. -GRegex normally treats such a pattern as though it were preceded by \A. -</p> -<p> -In cases where it is known that the string contains no newlines, it -is worth setting <code class="varname">G_REGEX_DOTALL</code> in order to obtain this optimization, -or alternatively using ^ to indicate anchoring explicitly. -</p> -<p> -However, there is one situation where the optimization cannot be used. -When .* is inside capturing parentheses that are the subject of a -backreference elsewhere in the pattern, a match at the start may fail -where a later one succeeds. Consider, for example: -</p> -<pre class="programlisting"> -(.*)abc\1 -</pre> -<p> -If the string is "xyz123abc123" the match point is the fourth character. -For this reason, such a pattern is not implicitly anchored. -</p> -<p> -When a capturing subpattern is repeated, the value captured is the -substring that matched the final iteration. For example, after -</p> -<pre class="programlisting"> -(tweedle[dume]{3}\s*)+ -</pre> -<p> -has matched "tweedledum tweedledee" the value of the captured substring -is "tweedledee". However, if there are nested capturing subpatterns, -the corresponding captured values may have been set in previous iterations. -For example, after -</p> -<pre class="programlisting"> -/(a|(b))+/ -</pre> -<p> -matches "aba" the value of the second captured substring is "b". -</p> -</div> -<div class="refsect1"> -<a name="idp40906160"></a><h2>Atomic grouping and possessive quantifiers</h2> -<p> -With both maximizing ("greedy") and minimizing ("ungreedy" or "lazy") -repetition, failure of what follows normally causes the repeated -item to be re-evaluated to see if a different number -of repeats allows the rest of the pattern to match. Sometimes it -is useful to prevent this, either to change the nature of the -match, or to cause it fail earlier than it otherwise might, when the -author of the pattern knows there is no point in carrying on. -</p> -<p> -Consider, for example, the pattern \d+foo when applied to the string -</p> -<pre class="programlisting"> -123456bar -</pre> -<p> -After matching all 6 digits and then failing to match "foo", the normal -action of the matcher is to try again with only 5 digits matching the -\d+ item, and then with 4, and so on, before ultimately failing. -"Atomic grouping" (a term taken from Jeffrey Friedl’s book) provides -the means for specifying that once a subpattern has matched, it is not -to be re-evaluated in this way. -</p> -<p> -If we use atomic grouping for the previous example, the matcher -give up immediately on failing to match "foo" the first time. The notation -is a kind of special parenthesis, starting with (?> as in this -example: -</p> -<pre class="programlisting"> -(?>\d+)foo -</pre> -<p> -This kind of parenthesis "locks up" the part of the pattern it contains -once it has matched, and a failure further into the pattern is -prevented from backtracking into it. Backtracking past it to previous -items, however, works as normal. -</p> -<p> -An alternative description is that a subpattern of this type matches -the string of characters that an identical standalone pattern would -match, if anchored at the current point in the string. -</p> -<p> -Atomic grouping subpatterns are not capturing subpatterns. Simple cases -such as the above example can be thought of as a maximizing repeat that -must swallow everything it can. So, while both \d+ and \d+? are prepared -to adjust the number of digits they match in order to make the -rest of the pattern match, (?>\d+) can only match an entire sequence of -digits. -</p> -<p> -Atomic groups in general can of course contain arbitrarily complicated -subpatterns, and can be nested. However, when the subpattern for an -atomic group is just a single repeated item, as in the example above, a -simpler notation, called a "possessive quantifier" can be used. This -consists of an additional + character following a quantifier. Using -this notation, the previous example can be rewritten as -</p> -<pre class="programlisting"> -\d++foo -</pre> -<p> -Possessive quantifiers are always greedy; the setting of the -<code class="varname">G_REGEX_UNGREEDY</code> option is ignored. They are a convenient notation for the -simpler forms of atomic group. However, there is no difference in the -meaning of a possessive quantifier and the equivalent -atomic group, though there may be a performance difference; -possessive quantifiers should be slightly faster. -</p> -<p> -The possessive quantifier syntax is an extension to the Perl syntax. -It was invented by Jeffrey Friedl in the first edition of his book and -then implemented by Mike McCloskey in Sun's Java package. -It ultimately found its way into Perl at release 5.10. -</p> -<p> -GRegex has an optimization that automatically "possessifies" certain simple -pattern constructs. For example, the sequence A+B is treated as A++B because -there is no point in backtracking into a sequence of A's when B must follow. -</p> -<p> -When a pattern contains an unlimited repeat inside a subpattern that -can itself be repeated an unlimited number of times, the use of an -atomic group is the only way to avoid some failing matches taking a -very long time indeed. The pattern -</p> -<pre class="programlisting"> -(\D+|<\d+>)*[!?] -</pre> -<p> -matches an unlimited number of substrings that either consist of non- -digits, or digits enclosed in <>, followed by either ! or ?. When it -matches, it runs quickly. However, if it is applied to -</p> -<pre class="programlisting"> -aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa -</pre> -<p> -it takes a long time before reporting failure. This is because the -string can be divided between the internal \D+ repeat and the external -* repeat in a large number of ways, and all have to be tried. (The -example uses [!?] rather than a single character at the end, because -GRegex has an optimization that allows for fast failure -when a single character is used. It remember the last single character -that is required for a match, and fail early if it is not present -in the string.) If the pattern is changed so that it uses an atomic -group, like this: -</p> -<pre class="programlisting"> -((?>\D+)|<\d+>)*[!?] -</pre> -<p> -sequences of non-digits cannot be broken, and failure happens quickly. -</p> -</div> -<div class="refsect1"> -<a name="idp40922144"></a><h2>Back references</h2> -<p> -Outside a character class, a backslash followed by a digit greater than -0 (and possibly further digits) is a back reference to a capturing subpattern -earlier (that is, to its left) in the pattern, provided there have been that -many previous capturing left parentheses. -</p> -<p> -However, if the decimal number following the backslash is less than 10, -it is always taken as a back reference, and causes an error only if -there are not that many capturing left parentheses in the entire pattern. -In other words, the parentheses that are referenced need not be -to the left of the reference for numbers less than 10. A "forward back -reference" of this type can make sense when a repetition is involved and -the subpattern to the right has participated in an earlier iteration. -</p> -<p> -It is not possible to have a numerical "forward back reference" to subpattern -whose number is 10 or more using this syntax because a sequence such as \e50 is -interpreted as a character defined in octal. See the subsection entitled -"Non-printing characters" above for further details of the handling of digits -following a backslash. There is no such problem when named parentheses are used. -A back reference to any subpattern is possible using named parentheses (see below). -</p> -<p> -Another way of avoiding the ambiguity inherent in the use of digits following a -backslash is to use the \g escape sequence (introduced in Perl 5.10.) -This escape must be followed by a positive or a negative number, -optionally enclosed in braces. -</p> -<p> -A positive number specifies an absolute reference without the ambiguity that is -present in the older syntax. It is also useful when literal digits follow the -reference. A negative number is a relative reference. Consider "(abc(def)ghi)\g{-1}", -the sequence \g{-1} is a reference to the most recently started capturing -subpattern before \g, that is, is it equivalent to \2. Similarly, \g{-2} -would be equivalent to \1. The use of relative references can be helpful in -long patterns, and also in patterns that are created by joining together -fragments that contain references within themselves. -</p> -<p> -A back reference matches whatever actually matched the capturing subpattern -in the current string, rather than anything matching -the subpattern itself (see "Subpatterns as subroutines" below for a way -of doing that). So the pattern -</p> -<pre class="programlisting"> -(sens|respons)e and \1ibility -</pre> -<p> -matches "sense and sensibility" and "response and responsibility", but -not "sense and responsibility". If caseful matching is in force at the -time of the back reference, the case of letters is relevant. For example, -</p> -<pre class="programlisting"> -((?i)rah)\s+\1 -</pre> -<p> -matches "rah rah" and "RAH RAH", but not "RAH rah", even though the -original capturing subpattern is matched caselessly. -</p> -<p> -Back references to named subpatterns use the Perl syntax \k<name> or \k'name' -or the Python syntax (?P=name). We could rewrite the above example in either of -the following ways: -</p> -<pre class="programlisting"> -(?<p1>(?i)rah)\s+\k<p1> -(?P<p1>(?i)rah)\s+(?P=p1) -</pre> -<p> -A subpattern that is referenced by name may appear in the pattern before or -after the reference. -</p> -<p> -There may be more than one back reference to the same subpattern. If a -subpattern has not actually been used in a particular match, any back -references to it always fail. For example, the pattern -</p> -<pre class="programlisting"> -(a|(bc))\2 -</pre> -<p> -always fails if it starts to match "a" rather than "bc". Because there -may be many capturing parentheses in a pattern, all digits following -the backslash are taken as part of a potential back reference number. -If the pattern continues with a digit character, some delimiter must be -used to terminate the back reference. If the <code class="varname">G_REGEX_EXTENDED</code> flag is -set, this can be whitespace. Otherwise an empty comment (see "Comments" below) can be used. -</p> -<p> -A back reference that occurs inside the parentheses to which it refers -fails when the subpattern is first used, so, for example, (a\1) never -matches. However, such references can be useful inside repeated subpatterns. -For example, the pattern -</p> -<pre class="programlisting"> -(a|b\1)+ -</pre> -<p> -matches any number of "a"s and also "aba", "ababbaa" etc. At each iteration -of the subpattern, the back reference matches the character -string corresponding to the previous iteration. In order for this to -work, the pattern must be such that the first iteration does not need -to match the back reference. This can be done using alternation, as in -the example above, or by a quantifier with a minimum of zero. -</p> -</div> -<div class="refsect1"> -<a name="idp40937328"></a><h2>Assertions</h2> -<p> -An assertion is a test on the characters following or preceding the -current matching point that does not actually consume any characters. -The simple assertions coded as \b, \B, \A, \G, \Z, \z, ^ and $ are -described above. -</p> -<p> -More complicated assertions are coded as subpatterns. There are two -kinds: those that look ahead of the current position in the -string, and those that look behind it. An assertion subpattern is -matched in the normal way, except that it does not cause the current -matching position to be changed. -</p> -<p> -Assertion subpatterns are not capturing subpatterns, and may not be -repeated, because it makes no sense to assert the same thing several -times. If any kind of assertion contains capturing subpatterns within -it, these are counted for the purposes of numbering the capturing -subpatterns in the whole pattern. However, substring capturing is carried -out only for positive assertions, because it does not make sense for -negative assertions. -</p> -<div class="refsect2"> -<a name="idp40940320"></a><h3>Lookahead assertions</h3> -<p> -Lookahead assertions start with (?= for positive assertions and (?! for -negative assertions. For example, -</p> -<pre class="programlisting"> -\w+(?=;) -</pre> -<p> -matches a word followed by a semicolon, but does not include the semicolon -in the match, and -</p> -<pre class="programlisting"> -foo(?!bar) -</pre> -<p> -matches any occurrence of "foo" that is not followed by "bar". Note -that the apparently similar pattern -</p> -<pre class="programlisting"> -(?!foo)bar -</pre> -<p> -does not find an occurrence of "bar" that is preceded by something -other than "foo"; it finds any occurrence of "bar" whatsoever, because -the assertion (?!foo) is always true when the next three characters are -"bar". A lookbehind assertion is needed to achieve the other effect. -</p> -<p> -If you want to force a matching failure at some point in a pattern, the -most convenient way to do it is with (?!) because an empty string -always matches, so an assertion that requires there not to be an empty -string must always fail. -</p> -</div> -<hr> -<div class="refsect2"> -<a name="idp40946384"></a><h3>Lookbehind assertions</h3> -<p> -Lookbehind assertions start with (?<= for positive assertions and (?<! -for negative assertions. For example, -</p> -<pre class="programlisting"> -(?<!foo)bar -</pre> -<p> -does find an occurrence of "bar" that is not preceded by "foo". The -contents of a lookbehind assertion are restricted such that all the -strings it matches must have a fixed length. However, if there are -several top-level alternatives, they do not all have to have the same -fixed length. Thus -</p> -<pre class="programlisting"> -(?<=bullock|donkey) -</pre> -<p> -is permitted, but -</p> -<pre class="programlisting"> -(?<!dogs?|cats?) -</pre> -<p> -causes an error at compile time. Branches that match different length -strings are permitted only at the top level of a lookbehind assertion. -An assertion such as -</p> -<pre class="programlisting"> -(?<=ab(c|de)) -</pre> -<p> -is not permitted, because its single top-level branch can match two -different lengths, but it is acceptable if rewritten to use two top- -level branches: -</p> -<pre class="programlisting"> -(?<=abc|abde) -</pre> -<p> -The implementation of lookbehind assertions is, for each alternative, -to temporarily move the current position back by the fixed length and -then try to match. If there are insufficient characters before the -current position, the assertion fails. -</p> -<p> -GRegex does not allow the \C escape (which matches a single byte in UTF-8 -mode) to appear in lookbehind assertions, because it makes it impossible -to calculate the length of the lookbehind. The \X and \R escapes, which can -match different numbers of bytes, are also not permitted. -</p> -<p> -Possessive quantifiers can be used in conjunction with lookbehind assertions to -specify efficient matching at the end of the subject string. Consider a simple -pattern such as -</p> -<pre class="programlisting"> -abcd$ -</pre> -<p> -when applied to a long string that does not match. Because matching -proceeds from left to right, GRegex will look for each "a" in the string -and then see if what follows matches the rest of the pattern. If the -pattern is specified as -</p> -<pre class="programlisting"> -^.*abcd$ -</pre> -<p> -the initial .* matches the entire string at first, but when this fails -(because there is no following "a"), it backtracks to match all but the -last character, then all but the last two characters, and so on. Once -again the search for "a" covers the entire string, from right to left, -so we are no better off. However, if the pattern is written as -</p> -<pre class="programlisting"> -^.*+(?<=abcd) -</pre> -<p> -there can be no backtracking for the .*+ item; it can match only the -entire string. The subsequent lookbehind assertion does a single test -on the last four characters. If it fails, the match fails immediately. -For long strings, this approach makes a significant difference to the -processing time. -</p> -</div> -<hr> -<div class="refsect2"> -<a name="idp40960128"></a><h3>Using multiple assertions</h3> -<p> -Several assertions (of any sort) may occur in succession. For example, -</p> -<pre class="programlisting"> -(?<=\d{3})(?<!999)foo -</pre> -<p> -matches "foo" preceded by three digits that are not "999". Notice that -each of the assertions is applied independently at the same point in -the string. First there is a check that the previous three -characters are all digits, and then there is a check that the same -three characters are not "999". This pattern does not match "foo" preceded -by six characters, the first of which are digits and the last -three of which are not "999". For example, it doesn’t match "123abcfoo". -A pattern to do that is -</p> -<pre class="programlisting"> -(?<=\d{3}...)(?<!999)foo -</pre> -<p> -This time the first assertion looks at the preceding six characters, -checking that the first three are digits, and then the second assertion -checks that the preceding three characters are not "999". -</p> -<p> -Assertions can be nested in any combination. For example, -</p> -<pre class="programlisting"> -(?<=(?<!foo)bar)baz -</pre> -<p> -matches an occurrence of "baz" that is preceded by "bar" which in turn -is not preceded by "foo", while -</p> -<pre class="programlisting"> -(?<=\d{3}(?!999)...)foo -</pre> -<p> -is another pattern that matches "foo" preceded by three digits and any -three characters that are not "999". -</p> -</div> -</div> -<div class="refsect1"> -<a name="idp40967600"></a><h2>Conditional subpatterns</h2> -<p> -It is possible to cause the matching process to obey a subpattern -conditionally or to choose between two alternative subpatterns, depending -on the result of an assertion, or whether a previous capturing subpattern -matched or not. The two possible forms of conditional subpattern are -</p> -<pre class="programlisting"> -(?(condition)yes-pattern) -(?(condition)yes-pattern|no-pattern) -</pre> -<p> -If the condition is satisfied, the yes-pattern is used; otherwise the -no-pattern (if present) is used. If there are more than two alternatives -in the subpattern, a compile-time error occurs. -</p> -<p> -There are four kinds of condition: references to subpatterns, references to -recursion, a pseudo-condition called DEFINE, and assertions. -</p> -<div class="refsect2"> -<a name="idp40970944"></a><h3>Checking for a used subpattern by number</h3> -<p> -If the text between the parentheses consists of a sequence of digits, the -condition is true if the capturing subpattern of that number has previously -matched. -</p> -<p> -Consider the following pattern, which contains non-significant white space -to make it more readable (assume the <code class="varname">G_REGEX_EXTENDED</code>) -and to divide it into three parts for ease of discussion: -</p> -<pre class="programlisting"> -( \( )? [^()]+ (?(1) \) ) -</pre> -<p> -The first part matches an optional opening parenthesis, and if that -character is present, sets it as the first captured substring. The second -part matches one or more characters that are not parentheses. The -third part is a conditional subpattern that tests whether the first set -of parentheses matched or not. If they did, that is, if string started -with an opening parenthesis, the condition is true, and so the yes-pattern -is executed and a closing parenthesis is required. Otherwise, -since no-pattern is not present, the subpattern matches nothing. In -other words, this pattern matches a sequence of non-parentheses, -optionally enclosed in parentheses. -</p> -</div> -<hr> -<div class="refsect2"> -<a name="idp40975184"></a><h3>Checking for a used subpattern by name</h3> -<p> -Perl uses the syntax (?(<name>)...) or (?('name')...) to test for a used -subpattern by name, the Python syntax (?(name)...) is also recognized. However, -there is a possible ambiguity with this syntax, because subpattern names may -consist entirely of digits. GRegex looks first for a named subpattern; if it -cannot find one and the name consists entirely of digits, GRegex looks for a -subpattern of that number, which must be greater than zero. Using subpattern -names that consist entirely of digits is not recommended. -</p> -<p> -Rewriting the above example to use a named subpattern gives this: -</p> -<pre class="programlisting"> -(?<OPEN> \( )? [^()]+ (?(<OPEN>) \) ) -</pre> -</div> -<hr> -<div class="refsect2"> -<a name="idp40978160"></a><h3>Checking for pattern recursion</h3> -<p> -If the condition is the string (R), and there is no subpattern with the name R, -the condition is true if a recursive call to the whole pattern or any -subpattern has been made. If digits or a name preceded by ampersand follow the -letter R, for example: -</p> -<pre class="programlisting"> -(?(R3)...) -(?(R&name)...) -</pre> -<p> -the condition is true if the most recent recursion is into the subpattern whose -number or name is given. This condition does not check the entire recursion -stack. -</p> -<p> -At "top level", all these recursion test conditions are false. Recursive -patterns are described below. -</p> -</div> -<hr> -<div class="refsect2"> -<a name="idp40981632"></a><h3>Defining subpatterns for use by reference only</h3> -<p> -If the condition is the string (DEFINE), and there is no subpattern with the -name DEFINE, the condition is always false. In this case, there may be only one -alternative in the subpattern. It is always skipped if control reaches this -point in the pattern; the idea of DEFINE is that it can be used to define -"subroutines" that can be referenced from elsewhere. (The use of "subroutines" -is described below.) For example, a pattern to match an IPv4 address could be -written like this (ignore whitespace and line breaks): -</p> -<pre class="programlisting"> -(?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) ) -\b (?&byte) (\.(?&byte)){3} \b -</pre> -<p> -The first part of the pattern is a DEFINE group inside which a another group -named "byte" is defined. This matches an individual component of an IPv4 -address (a number less than 256). When matching takes place, this part of the -pattern is skipped because DEFINE acts like a false condition. -</p> -<p> -The rest of the pattern uses references to the named group to match the four -dot-separated components of an IPv4 address, insisting on a word boundary at -each end. -</p> -</div> -<hr> -<div class="refsect2"> -<a name="idp40985568"></a><h3>Assertion conditions</h3> -<p> -If the condition is not in any of the above formats, it must be an -assertion. This may be a positive or negative lookahead or lookbehind -assertion. Consider this pattern, again containing non-significant -white space, and with the two alternatives on the second line: -</p> -<pre class="programlisting"> -(?(?=[^a-z]*[a-z]) -\d{2}-[a-z]{3}-\d{2} | \d{2}-\d{2}-\d{2} ) -</pre> -<p> -The condition is a positive lookahead assertion that matches an -optional sequence of non-letters followed by a letter. In other words, -it tests for the presence of at least one letter in the string. If a -letter is found, the string is matched against the first alternative; -otherwise it is matched against the second. This pattern matches -strings in one of the two forms dd-aaa-dd or dd-dd-dd, where aaa are -letters and dd are digits. -</p> -</div> -</div> -<div class="refsect1"> -<a name="idp40988880"></a><h2>Comments</h2> -<p> -The sequence (?# marks the start of a comment that continues up to the -next closing parenthesis. Nested parentheses are not permitted. The -characters that make up a comment play no part in the pattern matching -at all. -</p> -<p> -If the <code class="varname">G_REGEX_EXTENDED</code> option is set, an unescaped # -character outside a character class introduces a comment that continues to -immediately after the next newline in the pattern. -</p> -</div> -<div class="refsect1"> -<a name="idp40991472"></a><h2>Recursive patterns</h2> -<p> -Consider the problem of matching a string in parentheses, allowing for -unlimited nested parentheses. Without the use of recursion, the best -that can be done is to use a pattern that matches up to some fixed -depth of nesting. It is not possible to handle an arbitrary nesting -depth. -</p> -<p> -For some time, Perl has provided a facility that allows regular expressions to -recurse (amongst other things). It does this by interpolating Perl code in the -expression at run time, and the code can refer to the expression itself. A Perl -pattern using code interpolation to solve the parentheses problem can be -created like this: -</p> -<pre class="programlisting"> -$re = qr{\( (?: (?>[^()]+) | (?p{$re}) )* \)}x; -</pre> -<p> -The (?p{...}) item interpolates Perl code at run time, and in this case refers -recursively to the pattern in which it appears. -</p> -<p> -Obviously, GRegex cannot support the interpolation of Perl code. Instead, it -supports special syntax for recursion of the entire pattern, and also for -individual subpattern recursion. This kind of recursion was introduced into -Perl at release 5.10. -</p> -<p> -A special item that consists of (? followed by a number greater than zero and a -closing parenthesis is a recursive call of the subpattern of the given number, -provided that it occurs inside that subpattern. (If not, it is a "subroutine" -call, which is described in the next section.) The special item (?R) or (?0) is -a recursive call of the entire regular expression. -</p> -<p> -In GRegex (like Python, but unlike Perl), a recursive subpattern call is always -treated as an atomic group. That is, once it has matched some of the subject -string, it is never re-entered, even if it contains untried alternatives and -there is a subsequent matching failure. -</p> -<p> -This pattern solves the nested parentheses problem (assume the -<code class="varname">G_REGEX_EXTENDED</code> option is set so that white space is -ignored): -</p> -<pre class="programlisting"> -\( ( (?>[^()]+) | (?R) )* \) -</pre> -<p> -First it matches an opening parenthesis. Then it matches any number of -substrings which can either be a sequence of non-parentheses, or a -recursive match of the pattern itself (that is, a correctly parenthesized -substring). Finally there is a closing parenthesis. -</p> -<p> -If this were part of a larger pattern, you would not want to recurse -the entire pattern, so instead you could use this: -</p> -<pre class="programlisting"> -( \( ( (?>[^()]+) | (?1) )* \) ) -</pre> -<p> -We have put the pattern into parentheses, and caused the recursion to -refer to them instead of the whole pattern. In a larger pattern, keeping -track of parenthesis numbers can be tricky. It may be more convenient to -use named parentheses instead. -The Perl syntax for this is (?&name); GRegex also supports the(?P>name) -syntac. We could rewrite the above example as follows: -</p> -<pre class="programlisting"> -(?<pn> \( ( (?>[^()]+) | (?&pn) )* \) ) -</pre> -<p> -If there is more than one subpattern with the same name, the earliest one is -used. This particular example pattern contains nested unlimited repeats, and so -the use of atomic grouping for matching strings of non-parentheses is important -when applying the pattern to strings that do not match. -For example, when this pattern is applied to -</p> -<pre class="programlisting"> -(aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa() -</pre> -<p> -it yields "no match" quickly. However, if atomic grouping is not used, -the match runs for a very long time indeed because there are so many -different ways the + and * repeats can carve up the string, and all -have to be tested before failure can be reported. -</p> -<p> -At the end of a match, the values set for any capturing subpatterns are -those from the outermost level of the recursion at which the subpattern -value is set. - - - -If the pattern above is matched against -</p> -<pre class="programlisting"> -(ab(cd)ef) -</pre> -<p> -the value for the capturing parentheses is "ef", which is the last -value taken on at the top level. If additional parentheses are added, -giving -</p> -<pre class="programlisting"> -\( ( ( (?>[^()]+) | (?R) )* ) \) - ^ ^ - ^ ^ -</pre> -<p> -the string they capture is "ab(cd)ef", the contents of the top level -parentheses. -</p> -<p> -Do not confuse the (?R) item with the condition (R), which tests for -recursion. Consider this pattern, which matches text in angle brackets, -allowing for arbitrary nesting. Only digits are allowed in nested -brackets (that is, when recursing), whereas any characters are permitted -at the outer level. -</p> -<pre class="programlisting"> -< (?: (?(R) \d++ | [^<>]*+) | (?R)) * > -</pre> -<p> -In this pattern, (?(R) is the start of a conditional subpattern, with -two different alternatives for the recursive and non-recursive cases. -The (?R) item is the actual recursive call. -</p> -</div> -<div class="refsect1"> -<a name="idp41010080"></a><h2>Subpatterns as subroutines</h2> -<p> -If the syntax for a recursive subpattern reference (either by number or -by name) is used outside the parentheses to which it refers, it operates -like a subroutine in a programming language. The "called" subpattern may -be defined before or after the reference. An earlier example pointed out -that the pattern -</p> -<pre class="programlisting"> -(sens|respons)e and \1ibility -</pre> -<p> -matches "sense and sensibility" and "response and responsibility", but -not "sense and responsibility". If instead the pattern -</p> -<pre class="programlisting"> -(sens|respons)e and (?1)ibility -</pre> -<p> -is used, it does match "sense and responsibility" as well as the other -two strings. Another example is given in the discussion of DEFINE above. -</p> -<p> -Like recursive subpatterns, a "subroutine" call is always treated as an atomic -group. That is, once it has matched some of the string, it is never -re-entered, even if it contains untried alternatives and there is a subsequent -matching failure. -</p> -<p> -When a subpattern is used as a subroutine, processing options such as -case-independence are fixed when the subpattern is defined. They cannot be -changed for different calls. For example, consider this pattern: -</p> -<pre class="programlisting"> -(abc)(?i:(?1)) -</pre> -<p> -It matches "abcabc". It does not match "abcABC" because the change of -processing option does not affect the called subpattern. -</p> -</div> -<div class="refsect1"> -<a name="idp41018944"></a><h2>Copyright</h2> -<p> -This document was copied and adapted from the PCRE documentation, -specifically from the man page for pcrepattern. -The original copyright note is: -</p> -<pre class="programlisting"> -Copyright (c) 1997-2006 University of Cambridge. - -Redistribution and use in source and binary forms, with or without -modification, are permitted provided that the following conditions are met: - - * Redistributions of source code must retain the above copyright notice, - this list of conditions and the following disclaimer. - - * Redistributions in binary form must reproduce the above copyright - notice, this list of conditions and the following disclaimer in the - documentation and/or other materials provided with the distribution. - - * Neither the name of the University of Cambridge nor the name of Google - Inc. nor the names of their contributors may be used to endorse or - promote products derived from this software without specific prior - written permission. - -THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" -AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE -IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE -ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE -LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR -CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF -SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS -INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN -CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) -ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE -POSSIBILITY OF SUCH DAMAGE. -</pre> -</div> -</div> -<div class="footer"> -<hr> - Generated by GTK-Doc V1.18</div> -</body> -</html>
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