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192 lines
7.7 KiB
192 lines
7.7 KiB
4 months ago
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<head>
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<title>pcre2convert specification</title>
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</head>
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<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
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<h1>pcre2convert man page</h1>
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<p>
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Return to the <a href="index.html">PCRE2 index page</a>.
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</p>
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<p>
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This page is part of the PCRE2 HTML documentation. It was generated
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automatically from the original man page. If there is any nonsense in it,
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please consult the man page, in case the conversion went wrong.
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<br>
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<ul>
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<li><a name="TOC1" href="#SEC1">EXPERIMENTAL PATTERN CONVERSION FUNCTIONS</a>
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<li><a name="TOC2" href="#SEC2">THE CONVERT CONTEXT</a>
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<li><a name="TOC3" href="#SEC3">THE CONVERSION FUNCTION</a>
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<li><a name="TOC4" href="#SEC4">CONVERTING GLOBS</a>
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<li><a name="TOC5" href="#SEC5">CONVERTING POSIX PATTERNS</a>
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<li><a name="TOC6" href="#SEC6">AUTHOR</a>
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<li><a name="TOC7" href="#SEC7">REVISION</a>
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</ul>
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<br><a name="SEC1" href="#TOC1">EXPERIMENTAL PATTERN CONVERSION FUNCTIONS</a><br>
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<P>
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This document describes a set of functions that can be used to convert
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"foreign" patterns into PCRE2 regular expressions. This facility is currently
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experimental, and may be changed in future releases. Two kinds of pattern,
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globs and POSIX patterns, are supported.
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</P>
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<br><a name="SEC2" href="#TOC1">THE CONVERT CONTEXT</a><br>
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<P>
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<b>pcre2_convert_context *pcre2_convert_context_create(</b>
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<b> pcre2_general_context *<i>gcontext</i>);</b>
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<br>
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<br>
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<b>pcre2_convert_context *pcre2_convert_context_copy(</b>
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<b> pcre2_convert_context *<i>cvcontext</i>);</b>
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<br>
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<br>
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<b>void pcre2_convert_context_free(pcre2_convert_context *<i>cvcontext</i>);</b>
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<br>
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<br>
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<b>int pcre2_set_glob_escape(pcre2_convert_context *<i>cvcontext</i>,</b>
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<b> uint32_t <i>escape_char</i>);</b>
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<br>
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<br>
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<b>int pcre2_set_glob_separator(pcre2_convert_context *<i>cvcontext</i>,</b>
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<b> uint32_t <i>separator_char</i>);</b>
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<br>
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<br>
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A convert context is used to hold parameters that affect the way that pattern
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conversion works. Like all PCRE2 contexts, you need to use a context only if
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you want to override the defaults. There are the usual create, copy, and free
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functions. If custom memory management functions are set in a general context
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that is passed to <b>pcre2_convert_context_create()</b>, they are used for all
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memory management within the conversion functions.
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</P>
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<P>
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There are only two parameters in the convert context at present. Both apply
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only to glob conversions. The escape character defaults to grave accent under
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Windows, otherwise backslash. It can be set to zero, meaning no escape
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character, or to any punctuation character with a code point less than 256.
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The separator character defaults to backslash under Windows, otherwise forward
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slash. It can be set to forward slash, backslash, or dot.
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</P>
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<P>
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The two setting functions return zero on success, or PCRE2_ERROR_BADDATA if
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their second argument is invalid.
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</P>
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<br><a name="SEC3" href="#TOC1">THE CONVERSION FUNCTION</a><br>
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<P>
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<b>int pcre2_pattern_convert(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b>
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<b> uint32_t <i>options</i>, PCRE2_UCHAR **<i>buffer</i>,</b>
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<b> PCRE2_SIZE *<i>blength</i>, pcre2_convert_context *<i>cvcontext</i>);</b>
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<br>
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<br>
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<b>void pcre2_converted_pattern_free(PCRE2_UCHAR *<i>converted_pattern</i>);</b>
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<br>
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<br>
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The first two arguments of <b>pcre2_pattern_convert()</b> define the foreign
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pattern that is to be converted. The length may be given as
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PCRE2_ZERO_TERMINATED. The <b>options</b> argument defines how the pattern is to
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be processed. If the input is UTF, the PCRE2_CONVERT_UTF option should be set.
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PCRE2_CONVERT_NO_UTF_CHECK may also be set if you are sure the input is valid.
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One or more of the glob options, or one of the following POSIX options must be
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set to define the type of conversion that is required:
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<pre>
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PCRE2_CONVERT_GLOB
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PCRE2_CONVERT_GLOB_NO_WILD_SEPARATOR
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PCRE2_CONVERT_GLOB_NO_STARSTAR
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PCRE2_CONVERT_POSIX_BASIC
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PCRE2_CONVERT_POSIX_EXTENDED
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</pre>
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Details of the conversions are given below. The <b>buffer</b> and <b>blength</b>
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arguments define how the output is handled:
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</P>
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<P>
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If <b>buffer</b> is NULL, the function just returns the length of the converted
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pattern via <b>blength</b>. This is one less than the length of buffer needed,
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because a terminating zero is always added to the output.
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</P>
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<P>
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If <b>buffer</b> points to a NULL pointer, an output buffer is obtained using
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the allocator in the context or <b>malloc()</b> if no context is supplied. A
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pointer to this buffer is placed in the variable to which <b>buffer</b> points.
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When no longer needed the output buffer must be freed by calling
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<b>pcre2_converted_pattern_free()</b>. If this function is called with a NULL
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argument, it returns immediately without doing anything.
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</P>
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<P>
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If <b>buffer</b> points to a non-NULL pointer, <b>blength</b> must be set to the
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actual length of the buffer provided (in code units).
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</P>
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<P>
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In all cases, after successful conversion, the variable pointed to by
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<b>blength</b> is updated to the length actually used (in code units), excluding
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the terminating zero that is always added.
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</P>
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<P>
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If an error occurs, the length (via <b>blength</b>) is set to the offset
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within the input pattern where the error was detected. Only gross syntax errors
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are caught; there are plenty of errors that will get passed on for
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<b>pcre2_compile()</b> to discover.
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</P>
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<P>
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The return from <b>pcre2_pattern_convert()</b> is zero on success or a non-zero
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PCRE2 error code. Note that PCRE2 error codes may be positive or negative:
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<b>pcre2_compile()</b> uses mostly positive codes and <b>pcre2_match()</b>
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negative ones; <b>pcre2_convert()</b> uses existing codes of both kinds. A
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textual error message can be obtained by calling
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<b>pcre2_get_error_message()</b>.
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</P>
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<br><a name="SEC4" href="#TOC1">CONVERTING GLOBS</a><br>
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<P>
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Globs are used to match file names, and consequently have the concept of a
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"path separator", which defaults to backslash under Windows and forward slash
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otherwise. If PCRE2_CONVERT_GLOB is set, the wildcards * and ? are not
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permitted to match separator characters, but the double-star (**) feature
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(which does match separators) is supported.
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</P>
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<P>
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PCRE2_CONVERT_GLOB_NO_WILD_SEPARATOR matches globs with wildcards allowed to
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match separator characters. PCRE2_GLOB_NO_STARSTAR matches globs with the
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double-star feature disabled. These options may be given together.
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</P>
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<br><a name="SEC5" href="#TOC1">CONVERTING POSIX PATTERNS</a><br>
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<P>
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POSIX defines two kinds of regular expression pattern: basic and extended.
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These can be processed by setting PCRE2_CONVERT_POSIX_BASIC or
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PCRE2_CONVERT_POSIX_EXTENDED, respectively.
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</P>
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<P>
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In POSIX patterns, backslash is not special in a character class. Unmatched
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closing parentheses are treated as literals.
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</P>
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<P>
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In basic patterns, ? + | {} and () must be escaped to be recognized
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as metacharacters outside a character class. If the first character in the
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pattern is * it is treated as a literal. ^ is a metacharacter only at the start
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of a branch.
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</P>
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<P>
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In extended patterns, a backslash not in a character class always
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makes the next character literal, whatever it is. There are no backreferences.
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</P>
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<P>
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Note: POSIX mandates that the longest possible match at the first matching
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position must be found. This is not what <b>pcre2_match()</b> does; it yields
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the first match that is found. An application can use <b>pcre2_dfa_match()</b>
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to find the longest match, but that does not support backreferences (but then
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neither do POSIX extended patterns).
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</P>
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<br><a name="SEC6" href="#TOC1">AUTHOR</a><br>
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<P>
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Philip Hazel
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<br>
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University Computing Service
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<br>
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Cambridge, England.
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<br>
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</P>
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<br><a name="SEC7" href="#TOC1">REVISION</a><br>
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<P>
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Last updated: 28 June 2018
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<br>
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Copyright © 1997-2018 University of Cambridge.
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<br>
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<p>
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Return to the <a href="index.html">PCRE2 index page</a>.
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</p>
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