Documentation update.
This commit is contained in:
Philip.Hazel
parent
992e1fad44
commit
dc201313a6
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@ -42,18 +42,18 @@ the 16-bit library, which processes strings of 16-bit values, and one for the
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32-bit library, which processes strings of 32-bit values. There are no C++
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wrappers.
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The distribution does contain a set of C wrapper functions for the 8-bit
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library that are based on the POSIX regular expression API (see the pcre2posix
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man page). These can be found in a library called libpcre2-posix. Note that
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this just provides a POSIX calling interface to PCRE2; the regular expressions
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themselves still follow Perl syntax and semantics. The POSIX API is restricted,
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and does not give full access to all of PCRE2's facilities.
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In addition, the distribution contains a set of C wrapper functions for the
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8-bit library that are based on the POSIX regular expression API (see the
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pcre2posix man page). These are built into a library called libpcre2-posix.
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Note that this just provides a POSIX calling interface to PCRE2; the regular
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expressions themselves still follow Perl syntax and semantics. The POSIX API is
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restricted, and does not give full access to all of PCRE2's facilities.
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The header file for the POSIX-style functions is called pcre2posix.h. The
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official POSIX name is regex.h, but I did not want to risk possible problems
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with existing files of that name by distributing it that way. To use PCRE2 with
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an existing program that uses the POSIX API, pcre2posix.h will have to be
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renamed or pointed at by a link.
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renamed or pointed at by a link (or the program modified, of course).
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If you are using the POSIX interface to PCRE2 and there is already a POSIX
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regex library installed on your system, as well as worrying about the regex.h
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@ -61,12 +61,11 @@ header file (as mentioned above), you must also take care when linking programs
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to ensure that they link with PCRE2's libpcre2-posix library. Otherwise they
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may pick up the POSIX functions of the same name from the other library.
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One way of avoiding this confusion is to compile PCRE2 with the addition of
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-Dregcomp=PCRE2regcomp (and similarly for the other POSIX functions) to the
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compiler flags (CFLAGS if you are using "configure" -- see below). This has the
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effect of renaming the functions so that the names no longer clash. Of course,
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you have to do the same thing for your applications, or write them using the
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new names.
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To help with this issue, the libpcre2-posix library provides alternative names
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for the POSIX functions. These are the POSIX names, prefixed with "pcre2_", for
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example, pcre2_regcomp(). If an application can be compiled to use the
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alternative names (for example by the use of -Dregcomp=pcre2_regcomp etc.) it
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can be sure of linking with the PCRE2 functions.
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Documentation for PCRE2
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@ -888,4 +887,4 @@ The distribution should contain the files listed below.
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Philip Hazel
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Email local part: ph10
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Email domain: cam.ac.uk
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Last updated: 17 June 2018
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Last updated: 19 September 2018
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@ -32,15 +32,30 @@ please consult the man page, in case the conversion went wrong.
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<b> int <i>cflags</i>);</b>
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<br>
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<br>
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<b>int pcre2_regcomp(regex_t *<i>preg</i>, const char *<i>pattern</i>,</b>
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<b> int <i>cflags</i>);</b>
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<br>
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<br>
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<b>int regexec(const regex_t *<i>preg</i>, const char *<i>string</i>,</b>
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<b> size_t <i>nmatch</i>, regmatch_t <i>pmatch</i>[], int <i>eflags</i>);</b>
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<br>
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<br>
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<b>int pcre2_regexec(const regex_t *<i>preg</i>, const char *<i>string</i>,</b>
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<b> size_t <i>nmatch</i>, regmatch_t <i>pmatch</i>[], int <i>eflags</i>);</b>
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<br>
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<br>
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<b>size_t regerror(int <i>errcode</i>, const regex_t *<i>preg</i>,</b>
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<b> char *<i>errbuf</i>, size_t <i>errbuf_size</i>);</b>
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<br>
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<br>
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<b>size_t pcre2_regerror(int <i>errcode</i>, const regex_t *<i>preg</i>,</b>
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<b> char *<i>errbuf</i>, size_t <i>errbuf_size</i>);</b>
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<br>
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<br>
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<b>void regfree(regex_t *<i>preg</i>);</b>
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<br>
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<br>
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<b>void pcre2_regfree(regex_t *<i>preg</i>);</b>
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</P>
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<br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br>
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<P>
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@ -60,6 +75,14 @@ command for linking an application that uses them. Because the POSIX functions
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call the native ones, it is also necessary to add <b>-lpcre2-8</b>.
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</P>
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<P>
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When another POSIX regex library is also installed, there is the possibility of
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linking an application with the wrong library. To help avoid this issue, the
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PCRE2 POSIX library provides alternative names for the functions, all starting
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with "pcre2_". If an application uses these names, possible ambiguity is
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avoided. In the following description, however, the standard POSIX function
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names are used.
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</P>
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<P>
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Those POSIX option bits that can reasonably be mapped to PCRE2 native options
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have been implemented. In addition, the option REG_EXTENDED is defined with the
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value zero. This has no effect, but since programs that are written to the
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@ -322,9 +345,9 @@ Cambridge, England.
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</P>
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<br><a name="SEC9" href="#TOC1">REVISION</a><br>
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<P>
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Last updated: 15 June 2017
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Last updated: 19 September 2018
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<br>
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Copyright © 1997-2017 University of Cambridge.
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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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224
doc/pcre2.txt
224
doc/pcre2.txt
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@ -9419,14 +9419,25 @@ SYNOPSIS
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int regcomp(regex_t *preg, const char *pattern,
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int cflags);
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int pcre2_regcomp(regex_t *preg, const char *pattern,
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int cflags);
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int regexec(const regex_t *preg, const char *string,
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size_t nmatch, regmatch_t pmatch[], int eflags);
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int pcre2_regexec(const regex_t *preg, const char *string,
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size_t nmatch, regmatch_t pmatch[], int eflags);
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size_t regerror(int errcode, const regex_t *preg,
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char *errbuf, size_t errbuf_size);
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size_t pcre2_regerror(int errcode, const regex_t *preg,
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char *errbuf, size_t errbuf_size);
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void regfree(regex_t *preg);
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void pcre2_regfree(regex_t *preg);
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DESCRIPTION
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@ -9444,42 +9455,49 @@ DESCRIPTION
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POSIX functions call the native ones, it is also necessary to add
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-lpcre2-8.
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Those POSIX option bits that can reasonably be mapped to PCRE2 native
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options have been implemented. In addition, the option REG_EXTENDED is
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defined with the value zero. This has no effect, but since programs
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that are written to the POSIX interface often use it, this makes it
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easier to slot in PCRE2 as a replacement library. Other POSIX options
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When another POSIX regex library is also installed, there is the possi-
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bility of linking an application with the wrong library. To help avoid
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this issue, the PCRE2 POSIX library provides alternative names for the
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functions, all starting with "pcre2_". If an application uses these
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names, possible ambiguity is avoided. In the following description,
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however, the standard POSIX function names are used.
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Those POSIX option bits that can reasonably be mapped to PCRE2 native
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options have been implemented. In addition, the option REG_EXTENDED is
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defined with the value zero. This has no effect, but since programs
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that are written to the POSIX interface often use it, this makes it
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easier to slot in PCRE2 as a replacement library. Other POSIX options
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are not even defined.
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There are also some options that are not defined by POSIX. These have
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been added at the request of users who want to make use of certain
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PCRE2-specific features via the POSIX calling interface or to add BSD
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There are also some options that are not defined by POSIX. These have
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been added at the request of users who want to make use of certain
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PCRE2-specific features via the POSIX calling interface or to add BSD
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or GNU functionality.
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When PCRE2 is called via these functions, it is only the API that is
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POSIX-like in style. The syntax and semantics of the regular expres-
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sions themselves are still those of Perl, subject to the setting of
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various PCRE2 options, as described below. "POSIX-like in style" means
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that the API approximates to the POSIX definition; it is not fully
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POSIX-compatible, and in multi-unit encoding domains it is probably
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When PCRE2 is called via these functions, it is only the API that is
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POSIX-like in style. The syntax and semantics of the regular expres-
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sions themselves are still those of Perl, subject to the setting of
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various PCRE2 options, as described below. "POSIX-like in style" means
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that the API approximates to the POSIX definition; it is not fully
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POSIX-compatible, and in multi-unit encoding domains it is probably
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even less compatible.
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The header for these functions is supplied as pcre2posix.h to avoid any
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potential clash with other POSIX libraries. It can, of course, be
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potential clash with other POSIX libraries. It can, of course, be
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renamed or aliased as regex.h, which is the "correct" name. It provides
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two structure types, regex_t for compiled internal forms, and reg-
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match_t for returning captured substrings. It also defines some con-
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stants whose names start with "REG_"; these are used for setting
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two structure types, regex_t for compiled internal forms, and reg-
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match_t for returning captured substrings. It also defines some con-
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stants whose names start with "REG_"; these are used for setting
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options and identifying error codes.
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COMPILING A PATTERN
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The function regcomp() is called to compile a pattern into an internal
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The function regcomp() is called to compile a pattern into an internal
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form. By default, the pattern is a C string terminated by a binary zero
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(but see REG_PEND below). The preg argument is a pointer to a regex_t
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(but see REG_PEND below). The preg argument is a pointer to a regex_t
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structure that is used as a base for storing information about the com-
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piled regular expression. (It is also used for input when REG_PEND is
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piled regular expression. (It is also used for input when REG_PEND is
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set.)
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The argument cflags is either zero, or contains one or more of the bits
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@ -9487,84 +9505,84 @@ COMPILING A PATTERN
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REG_DOTALL
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The PCRE2_DOTALL option is set when the regular expression is passed
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for compilation to the native function. Note that REG_DOTALL is not
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The PCRE2_DOTALL option is set when the regular expression is passed
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for compilation to the native function. Note that REG_DOTALL is not
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part of the POSIX standard.
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REG_ICASE
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The PCRE2_CASELESS option is set when the regular expression is passed
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The PCRE2_CASELESS option is set when the regular expression is passed
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for compilation to the native function.
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REG_NEWLINE
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The PCRE2_MULTILINE option is set when the regular expression is passed
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for compilation to the native function. Note that this does not mimic
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the defined POSIX behaviour for REG_NEWLINE (see the following sec-
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for compilation to the native function. Note that this does not mimic
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the defined POSIX behaviour for REG_NEWLINE (see the following sec-
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tion).
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REG_NOSPEC
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The PCRE2_LITERAL option is set when the regular expression is passed
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for compilation to the native function. This disables all meta charac-
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ters in the pattern, causing it to be treated as a literal string. The
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only other options that are allowed with REG_NOSPEC are REG_ICASE,
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REG_NOSUB, REG_PEND, and REG_UTF. Note that REG_NOSPEC is not part of
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The PCRE2_LITERAL option is set when the regular expression is passed
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for compilation to the native function. This disables all meta charac-
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ters in the pattern, causing it to be treated as a literal string. The
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only other options that are allowed with REG_NOSPEC are REG_ICASE,
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REG_NOSUB, REG_PEND, and REG_UTF. Note that REG_NOSPEC is not part of
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the POSIX standard.
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REG_NOSUB
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When a pattern that is compiled with this flag is passed to regexec()
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for matching, the nmatch and pmatch arguments are ignored, and no cap-
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When a pattern that is compiled with this flag is passed to regexec()
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for matching, the nmatch and pmatch arguments are ignored, and no cap-
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tured strings are returned. Versions of the PCRE library prior to 10.22
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used to set the PCRE2_NO_AUTO_CAPTURE compile option, but this no
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used to set the PCRE2_NO_AUTO_CAPTURE compile option, but this no
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longer happens because it disables the use of backreferences.
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REG_PEND
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If this option is set, the reg_endp field in the preg structure (which
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If this option is set, the reg_endp field in the preg structure (which
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has the type const char *) must be set to point to the character beyond
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the end of the pattern before calling regcomp(). The pattern itself may
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now contain binary zeros, which are treated as data characters. Without
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REG_PEND, a binary zero terminates the pattern and the re_endp field is
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ignored. This is a GNU extension to the POSIX standard and should be
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ignored. This is a GNU extension to the POSIX standard and should be
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used with caution in software intended to be portable to other systems.
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REG_UCP
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The PCRE2_UCP option is set when the regular expression is passed for
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compilation to the native function. This causes PCRE2 to use Unicode
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properties when matchine \d, \w, etc., instead of just recognizing
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The PCRE2_UCP option is set when the regular expression is passed for
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compilation to the native function. This causes PCRE2 to use Unicode
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properties when matchine \d, \w, etc., instead of just recognizing
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ASCII values. Note that REG_UCP is not part of the POSIX standard.
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REG_UNGREEDY
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The PCRE2_UNGREEDY option is set when the regular expression is passed
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for compilation to the native function. Note that REG_UNGREEDY is not
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The PCRE2_UNGREEDY option is set when the regular expression is passed
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for compilation to the native function. Note that REG_UNGREEDY is not
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part of the POSIX standard.
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REG_UTF
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The PCRE2_UTF option is set when the regular expression is passed for
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compilation to the native function. This causes the pattern itself and
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all data strings used for matching it to be treated as UTF-8 strings.
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The PCRE2_UTF option is set when the regular expression is passed for
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compilation to the native function. This causes the pattern itself and
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all data strings used for matching it to be treated as UTF-8 strings.
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Note that REG_UTF is not part of the POSIX standard.
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In the absence of these flags, no options are passed to the native
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function. This means the the regex is compiled with PCRE2 default
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semantics. In particular, the way it handles newline characters in the
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subject string is the Perl way, not the POSIX way. Note that setting
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In the absence of these flags, no options are passed to the native
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function. This means the the regex is compiled with PCRE2 default
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semantics. In particular, the way it handles newline characters in the
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subject string is the Perl way, not the POSIX way. Note that setting
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PCRE2_MULTILINE has only some of the effects specified for REG_NEWLINE.
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It does not affect the way newlines are matched by the dot metacharac-
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It does not affect the way newlines are matched by the dot metacharac-
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ter (they are not) or by a negative class such as [^a] (they are).
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The yield of regcomp() is zero on success, and non-zero otherwise. The
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preg structure is filled in on success, and one other member of the
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structure (as well as re_endp) is public: re_nsub contains the number
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The yield of regcomp() is zero on success, and non-zero otherwise. The
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preg structure is filled in on success, and one other member of the
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structure (as well as re_endp) is public: re_nsub contains the number
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of capturing subpatterns in the regular expression. Various error codes
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are defined in the header file.
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NOTE: If the yield of regcomp() is non-zero, you must not attempt to
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NOTE: If the yield of regcomp() is non-zero, you must not attempt to
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use the contents of the preg structure. If, for example, you pass it to
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regexec(), the result is undefined and your program is likely to crash.
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@ -9572,9 +9590,9 @@ COMPILING A PATTERN
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MATCHING NEWLINE CHARACTERS
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This area is not simple, because POSIX and Perl take different views of
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things. It is not possible to get PCRE2 to obey POSIX semantics, but
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things. It is not possible to get PCRE2 to obey POSIX semantics, but
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then PCRE2 was never intended to be a POSIX engine. The following table
|
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lists the different possibilities for matching newline characters in
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lists the different possibilities for matching newline characters in
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Perl and PCRE2:
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Default Change with
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@ -9595,25 +9613,25 @@ MATCHING NEWLINE CHARACTERS
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$ matches \n in middle no REG_NEWLINE
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^ matches \n in middle no REG_NEWLINE
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This behaviour is not what happens when PCRE2 is called via its POSIX
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API. By default, PCRE2's behaviour is the same as Perl's, except that
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there is no equivalent for PCRE2_DOLLAR_ENDONLY in Perl. In both PCRE2
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This behaviour is not what happens when PCRE2 is called via its POSIX
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API. By default, PCRE2's behaviour is the same as Perl's, except that
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there is no equivalent for PCRE2_DOLLAR_ENDONLY in Perl. In both PCRE2
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and Perl, there is no way to stop newline from matching [^a].
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Default POSIX newline handling can be obtained by setting PCRE2_DOTALL
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and PCRE2_DOLLAR_ENDONLY when calling pcre2_compile() directly, but
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there is no way to make PCRE2 behave exactly as for the REG_NEWLINE
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action. When using the POSIX API, passing REG_NEWLINE to PCRE2's reg-
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Default POSIX newline handling can be obtained by setting PCRE2_DOTALL
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and PCRE2_DOLLAR_ENDONLY when calling pcre2_compile() directly, but
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there is no way to make PCRE2 behave exactly as for the REG_NEWLINE
|
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action. When using the POSIX API, passing REG_NEWLINE to PCRE2's reg-
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comp() function causes PCRE2_MULTILINE to be passed to pcre2_compile(),
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and REG_DOTALL passes PCRE2_DOTALL. There is no way to pass PCRE2_DOL-
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and REG_DOTALL passes PCRE2_DOTALL. There is no way to pass PCRE2_DOL-
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LAR_ENDONLY.
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MATCHING A PATTERN
|
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|
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The function regexec() is called to match a compiled pattern preg
|
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against a given string, which is by default terminated by a zero byte
|
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(but see REG_STARTEND below), subject to the options in eflags. These
|
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The function regexec() is called to match a compiled pattern preg
|
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against a given string, which is by default terminated by a zero byte
|
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(but see REG_STARTEND below), subject to the options in eflags. These
|
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can be:
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REG_NOTBOL
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@ -9623,9 +9641,9 @@ MATCHING A PATTERN
|
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REG_NOTEMPTY
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The PCRE2_NOTEMPTY option is set when calling the underlying PCRE2
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matching function. Note that REG_NOTEMPTY is not part of the POSIX
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standard. However, setting this option can give more POSIX-like behav-
|
||||
The PCRE2_NOTEMPTY option is set when calling the underlying PCRE2
|
||||
matching function. Note that REG_NOTEMPTY is not part of the POSIX
|
||||
standard. However, setting this option can give more POSIX-like behav-
|
||||
iour in some situations.
|
||||
|
||||
REG_NOTEOL
|
||||
|
|
@ -9635,66 +9653,66 @@ MATCHING A PATTERN
|
|||
|
||||
REG_STARTEND
|
||||
|
||||
When this option is set, the subject string starts at string +
|
||||
pmatch[0].rm_so and ends at string + pmatch[0].rm_eo, which should
|
||||
point to the first character beyond the string. There may be binary
|
||||
zeros within the subject string, and indeed, using REG_STARTEND is the
|
||||
When this option is set, the subject string starts at string +
|
||||
pmatch[0].rm_so and ends at string + pmatch[0].rm_eo, which should
|
||||
point to the first character beyond the string. There may be binary
|
||||
zeros within the subject string, and indeed, using REG_STARTEND is the
|
||||
only way to pass a subject string that contains a binary zero.
|
||||
|
||||
Whatever the value of pmatch[0].rm_so, the offsets of the matched
|
||||
string and any captured substrings are still given relative to the
|
||||
start of string itself. (Before PCRE2 release 10.30 these were given
|
||||
relative to string + pmatch[0].rm_so, but this differs from other
|
||||
Whatever the value of pmatch[0].rm_so, the offsets of the matched
|
||||
string and any captured substrings are still given relative to the
|
||||
start of string itself. (Before PCRE2 release 10.30 these were given
|
||||
relative to string + pmatch[0].rm_so, but this differs from other
|
||||
implementations.)
|
||||
|
||||
This is a BSD extension, compatible with but not specified by IEEE
|
||||
Standard 1003.2 (POSIX.2), and should be used with caution in software
|
||||
intended to be portable to other systems. Note that a non-zero rm_so
|
||||
does not imply REG_NOTBOL; REG_STARTEND affects only the location and
|
||||
length of the string, not how it is matched. Setting REG_STARTEND and
|
||||
passing pmatch as NULL are mutually exclusive; the error REG_INVARG is
|
||||
This is a BSD extension, compatible with but not specified by IEEE
|
||||
Standard 1003.2 (POSIX.2), and should be used with caution in software
|
||||
intended to be portable to other systems. Note that a non-zero rm_so
|
||||
does not imply REG_NOTBOL; REG_STARTEND affects only the location and
|
||||
length of the string, not how it is matched. Setting REG_STARTEND and
|
||||
passing pmatch as NULL are mutually exclusive; the error REG_INVARG is
|
||||
returned.
|
||||
|
||||
If the pattern was compiled with the REG_NOSUB flag, no data about any
|
||||
matched strings is returned. The nmatch and pmatch arguments of
|
||||
If the pattern was compiled with the REG_NOSUB flag, no data about any
|
||||
matched strings is returned. The nmatch and pmatch arguments of
|
||||
regexec() are ignored (except possibly as input for REG_STARTEND).
|
||||
|
||||
The value of nmatch may be zero, and the value pmatch may be NULL
|
||||
(unless REG_STARTEND is set); in both these cases no data about any
|
||||
The value of nmatch may be zero, and the value pmatch may be NULL
|
||||
(unless REG_STARTEND is set); in both these cases no data about any
|
||||
matched strings is returned.
|
||||
|
||||
Otherwise, the portion of the string that was matched, and also any
|
||||
Otherwise, the portion of the string that was matched, and also any
|
||||
captured substrings, are returned via the pmatch argument, which points
|
||||
to an array of nmatch structures of type regmatch_t, containing the
|
||||
members rm_so and rm_eo. These contain the byte offset to the first
|
||||
to an array of nmatch structures of type regmatch_t, containing the
|
||||
members rm_so and rm_eo. These contain the byte offset to the first
|
||||
character of each substring and the offset to the first character after
|
||||
the end of each substring, respectively. The 0th element of the vector
|
||||
relates to the entire portion of string that was matched; subsequent
|
||||
the end of each substring, respectively. The 0th element of the vector
|
||||
relates to the entire portion of string that was matched; subsequent
|
||||
elements relate to the capturing subpatterns of the regular expression.
|
||||
Unused entries in the array have both structure members set to -1.
|
||||
|
||||
A successful match yields a zero return; various error codes are
|
||||
defined in the header file, of which REG_NOMATCH is the "expected"
|
||||
A successful match yields a zero return; various error codes are
|
||||
defined in the header file, of which REG_NOMATCH is the "expected"
|
||||
failure code.
|
||||
|
||||
|
||||
ERROR MESSAGES
|
||||
|
||||
The regerror() function maps a non-zero errorcode from either regcomp()
|
||||
or regexec() to a printable message. If preg is not NULL, the error
|
||||
or regexec() to a printable message. If preg is not NULL, the error
|
||||
should have arisen from the use of that structure. A message terminated
|
||||
by a binary zero is placed in errbuf. If the buffer is too short, only
|
||||
by a binary zero is placed in errbuf. If the buffer is too short, only
|
||||
the first errbuf_size - 1 characters of the error message are used. The
|
||||
yield of the function is the size of buffer needed to hold the whole
|
||||
message, including the terminating zero. This value is greater than
|
||||
yield of the function is the size of buffer needed to hold the whole
|
||||
message, including the terminating zero. This value is greater than
|
||||
errbuf_size if the message was truncated.
|
||||
|
||||
|
||||
MEMORY USAGE
|
||||
|
||||
Compiling a regular expression causes memory to be allocated and asso-
|
||||
ciated with the preg structure. The function regfree() frees all such
|
||||
memory, after which preg may no longer be used as a compiled expres-
|
||||
Compiling a regular expression causes memory to be allocated and asso-
|
||||
ciated with the preg structure. The function regfree() frees all such
|
||||
memory, after which preg may no longer be used as a compiled expres-
|
||||
sion.
|
||||
|
||||
|
||||
|
|
@ -9707,8 +9725,8 @@ AUTHOR
|
|||
|
||||
REVISION
|
||||
|
||||
Last updated: 15 June 2017
|
||||
Copyright (c) 1997-2017 University of Cambridge.
|
||||
Last updated: 19 September 2018
|
||||
Copyright (c) 1997-2018 University of Cambridge.
|
||||
------------------------------------------------------------------------------
|
||||
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue