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-revision 63 by nigel,
Sat Feb 24 21:40:03 2007 UTC
+revision 678 by ph10,
Sun Aug 28 15:23:03 2011 UTC
 Line 1
- .TH PCRE 3
+ .TH PCREAPI 3
  .SH NAME
  PCRE - Perl-compatible regular expressions
- .SH SYNOPSIS OF PCRE API
+ .SH "PCRE NATIVE API BASIC FUNCTIONS"
  .rs
  .sp
  .B #include <pcre.h>
  .PP
  .SM
- .br
+ .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
- .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,
  .ti +5n
- .B const char **\fIerrptr\fR, int *\fIerroffset\fR,
+ .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
  .ti +5n
- .B const unsigned char *\fItableptr\fR);
+ .B const unsigned char *\fItableptr\fP);
  .PP
- .br
+ .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
- .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,
  .ti +5n
- .B const char **\fIerrptr\fR);
+ .B int *\fIerrorcodeptr\fP,
+ .ti +5n
+ .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
+ .ti +5n
+ .B const unsigned char *\fItableptr\fP);
+ .PP
+ .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP,
+ .ti +5n
+ .B const char **\fIerrptr\fP);
  .PP
- .br
+ .B void pcre_free_study(pcre_extra *\fIextra\fP);
- .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"
+ .PP
+ .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
  .ti +5n
- .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,
+ .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
  .ti +5n
- .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);
+ .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
+ .
+ .
+ .SH "PCRE NATIVE API AUXILIARY FUNCTIONS"
+ .rs
+ .sp
+ .B pcre_jit_stack *pcre_jit_stack_alloc(int \fIstartsize\fP, int \fImaxsize\fP);
+ .PP
+ .B void pcre_jit_stack_free(pcre_jit_stack *\fIstack\fP);
  .PP
- .br
+ .B void pcre_assign_jit_stack(pcre_extra *\fIextra\fP,
- .B int pcre_copy_named_substring(const pcre *\fIcode\fR,
  .ti +5n
- .B const char *\fIsubject\fR, int *\fIovector\fR,
+ .B pcre_jit_callback \fIcallback\fP, void *\fIdata\fP);
+ .PP
+ .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
+ .ti +5n
+ .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
  .ti +5n
- .B int \fIstringcount\fR, const char *\fIstringname\fR,
+ .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
  .ti +5n
- .B char *\fIbuffer\fR, int \fIbuffersize\fR);
+ .B int *\fIworkspace\fP, int \fIwscount\fP);
  .PP
- .br
+ .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
- .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,
  .ti +5n
- .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,
+ .B const char *\fIsubject\fP, int *\fIovector\fP,
  .ti +5n
- .B int \fIbuffersize\fR);
+ .B int \fIstringcount\fP, const char *\fIstringname\fP,
+ .ti +5n
+ .B char *\fIbuffer\fP, int \fIbuffersize\fP);
  .PP
- .br
+ .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
- .B int pcre_get_named_substring(const pcre *\fIcode\fR,
  .ti +5n
- .B const char *\fIsubject\fR, int *\fIovector\fR,
+ .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
  .ti +5n
- .B int \fIstringcount\fR, const char *\fIstringname\fR,
+ .B int \fIbuffersize\fP);
+ .PP
+ .B int pcre_get_named_substring(const pcre *\fIcode\fP,
  .ti +5n
- .B const char **\fIstringptr\fR);
+ .B const char *\fIsubject\fP, int *\fIovector\fP,
+ .ti +5n
+ .B int \fIstringcount\fP, const char *\fIstringname\fP,
+ .ti +5n
+ .B const char **\fIstringptr\fP);
  .PP
- .br
+ .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
- .B int pcre_get_stringnumber(const pcre *\fIcode\fR,
  .ti +5n
- .B const char *\fIname\fR);
+ .B const char *\fIname\fP);
  .PP
- .br
+ .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
- .B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR,
  .ti +5n
- .B int \fIstringcount\fR, int \fIstringnumber\fR,
+ .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
+ .PP
+ .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
  .ti +5n
- .B const char **\fIstringptr\fR);
+ .B int \fIstringcount\fP, int \fIstringnumber\fP,
+ .ti +5n
+ .B const char **\fIstringptr\fP);
  .PP
- .br
+ .B int pcre_get_substring_list(const char *\fIsubject\fP,
- .B int pcre_get_substring_list(const char *\fIsubject\fR,
  .ti +5n
- .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"
+ .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
  .PP
- .br
+ .B void pcre_free_substring(const char *\fIstringptr\fP);
- .B void pcre_free_substring(const char *\fIstringptr\fR);
  .PP
- .br
+ .B void pcre_free_substring_list(const char **\fIstringptr\fP);
- .B void pcre_free_substring_list(const char **\fIstringptr\fR);
  .PP
- .br
  .B const unsigned char *pcre_maketables(void);
  .PP
- .br
+ .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
- .B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"
  .ti +5n
- .B int \fIwhat\fR, void *\fIwhere\fR);
+ .B int \fIwhat\fP, void *\fIwhere\fP);
+ .PP
+ .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
+ .B *\fIfirstcharptr\fP);
  .PP
- .br
+ .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
- .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int
- .B *\fIfirstcharptr\fR);
  .PP
- .br
+ .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
- .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);
  .PP
- .br
  .B char *pcre_version(void);
  .PP
- .br
  .B void *(*pcre_malloc)(size_t);
  .PP
- .br
  .B void (*pcre_free)(void *);
  .PP
- .br
+ .B void *(*pcre_stack_malloc)(size_t);
+ .PP
+ .B void (*pcre_stack_free)(void *);
+ .PP
  .B int (*pcre_callout)(pcre_callout_block *);
+ .
- .SH PCRE API
+ .
+ .SH "PCRE API OVERVIEW"
  .rs
  .sp
- PCRE has its own native API, which is described in this document. There is also
+ PCRE has its own native API, which is described in this document. There are
- a set of wrapper functions that correspond to the POSIX regular expression API.
+ also some wrapper functions that correspond to the POSIX regular expression
- These are described in the \fBpcreposix\fR documentation.
+ API, but they do not give access to all the functionality. They are described
+ in the
- The native API function prototypes are defined in the header file \fBpcre.h\fR,
+ .\" HREF
- and on Unix systems the library itself is called \fBlibpcre.a\fR, so can be
+ \fBpcreposix\fP
- accessed by adding \fB-lpcre\fR to the command for linking an application which
+ .\"
- calls it. The header file defines the macros PCRE_MAJOR and PCRE_MINOR to
+ documentation. Both of these APIs define a set of C function calls. A C++
- contain the major and minor release numbers for the library. Applications can
+ wrapper is also distributed with PCRE. It is documented in the
- use these to include support for different releases.
+ .\" HREF
+ \fBpcrecpp\fP
- The functions \fBpcre_compile()\fR, \fBpcre_study()\fR, and \fBpcre_exec()\fR
+ .\"
- are used for compiling and matching regular expressions. A sample program that
+ page.
- demonstrates the simplest way of using them is given in the file
+ .P
- \fIpcredemo.c\fR. The \fBpcresample\fR documentation describes how to run it.
+ The native API C function prototypes are defined in the header file
+ \fBpcre.h\fP, and on Unix systems the library itself is called \fBlibpcre\fP.
- There are convenience functions for extracting captured substrings from a
+ It can normally be accessed by adding \fB-lpcre\fP to the command for linking
- matched subject string. They are:
+ an application that uses PCRE. The header file defines the macros PCRE_MAJOR
+ and PCRE_MINOR to contain the major and minor release numbers for the library.
-   \fBpcre_copy_substring()\fR
+ Applications can use these to include support for different releases of PCRE.
-   \fBpcre_copy_named_substring()\fR
+ .P
-   \fBpcre_get_substring()\fR
+ In a Windows environment, if you want to statically link an application program
-   \fBpcre_get_named_substring()\fR
+ against a non-dll \fBpcre.a\fP file, you must define PCRE_STATIC before
-   \fBpcre_get_substring_list()\fR
+ including \fBpcre.h\fP or \fBpcrecpp.h\fP, because otherwise the
+ \fBpcre_malloc()\fP and \fBpcre_free()\fP exported functions will be declared
- \fBpcre_free_substring()\fR and \fBpcre_free_substring_list()\fR are also
+ \fB__declspec(dllimport)\fP, with unwanted results.
+ .P
+ The functions \fBpcre_compile()\fP, \fBpcre_compile2()\fP, \fBpcre_study()\fP,
+ and \fBpcre_exec()\fP are used for compiling and matching regular expressions
+ in a Perl-compatible manner. A sample program that demonstrates the simplest
+ way of using them is provided in the file called \fIpcredemo.c\fP in the PCRE
+ source distribution. A listing of this program is given in the
+ .\" HREF
+ \fBpcredemo\fP
+ .\"
+ documentation, and the
+ .\" HREF
+ \fBpcresample\fP
+ .\"
+ documentation describes how to compile and run it.
+ .P
+ Just-in-time compiler support is an optional feature of PCRE that can be built
+ in appropriate hardware environments. It greatly speeds up the matching
+ performance of many patterns. Simple programs can request its use if available.
+ More complicated programs might need to make use of the
+ \fBpcre_jit_stack_alloc()\fP, \fBpcre_jit_stack_free()\fP, and
+ \fBpcre_assign_jit_stack()\fP functions in order to control its memory usage.
+ These functions are discussed in the
+ .\" HREF
+ \fBpcrejit\fP
+ .\"
+ documentation.
+ .P
+ A second matching function, \fBpcre_dfa_exec()\fP, which is not
+ Perl-compatible, is also provided. This uses a different algorithm for the
+ matching. The alternative algorithm finds all possible matches (at a given
+ point in the subject), and scans the subject just once (unless there are
+ lookbehind assertions). However, this algorithm does not return captured
+ substrings. A description of the two matching algorithms and their advantages
+ and disadvantages is given in the
+ .\" HREF
+ \fBpcrematching\fP
+ .\"
+ documentation.
+ .P
+ In addition to the main compiling and matching functions, there are convenience
+ functions for extracting captured substrings from a subject string that is
+ matched by \fBpcre_exec()\fP. They are:
+ .sp
+   \fBpcre_copy_substring()\fP
+   \fBpcre_copy_named_substring()\fP
+   \fBpcre_get_substring()\fP
+   \fBpcre_get_named_substring()\fP
+   \fBpcre_get_substring_list()\fP
+   \fBpcre_get_stringnumber()\fP
+   \fBpcre_get_stringtable_entries()\fP
+ .sp
+ \fBpcre_free_substring()\fP and \fBpcre_free_substring_list()\fP are also
  provided, to free the memory used for extracted strings.
+ .P
- The function \fBpcre_maketables()\fR is used (optionally) to build a set of
+ The function \fBpcre_maketables()\fP is used to build a set of character tables
- character tables in the current locale for passing to \fBpcre_compile()\fR.
+ in the current locale for passing to \fBpcre_compile()\fP, \fBpcre_exec()\fP,
+ or \fBpcre_dfa_exec()\fP. This is an optional facility that is provided for
- The function \fBpcre_fullinfo()\fR is used to find out information about a
+ specialist use. Most commonly, no special tables are passed, in which case
- compiled pattern; \fBpcre_info()\fR is an obsolete version which returns only
+ internal tables that are generated when PCRE is built are used.
+ .P
+ The function \fBpcre_fullinfo()\fP is used to find out information about a
+ compiled pattern; \fBpcre_info()\fP is an obsolete version that returns only
  some of the available information, but is retained for backwards compatibility.
- The function \fBpcre_version()\fR returns a pointer to a string containing the
+ The function \fBpcre_version()\fP returns a pointer to a string containing the
  version of PCRE and its date of release.
+ .P
- The global variables \fBpcre_malloc\fR and \fBpcre_free\fR initially contain
+ The function \fBpcre_refcount()\fP maintains a reference count in a data block
- the entry points of the standard \fBmalloc()\fR and \fBfree()\fR functions
+ containing a compiled pattern. This is provided for the benefit of
+ object-oriented applications.
+ .P
+ The global variables \fBpcre_malloc\fP and \fBpcre_free\fP initially contain
+ the entry points of the standard \fBmalloc()\fP and \fBfree()\fP functions,
  respectively. PCRE calls the memory management functions via these variables,
  so a calling program can replace them if it wishes to intercept the calls. This
  should be done before calling any PCRE functions.
+ .P
- The global variable \fBpcre_callout\fR initially contains NULL. It can be set
+ The global variables \fBpcre_stack_malloc\fP and \fBpcre_stack_free\fP are also
+ indirections to memory management functions. These special functions are used
+ only when PCRE is compiled to use the heap for remembering data, instead of
+ recursive function calls, when running the \fBpcre_exec()\fP function. See the
+ .\" HREF
+ \fBpcrebuild\fP
+ .\"
+ documentation for details of how to do this. It is a non-standard way of
+ building PCRE, for use in environments that have limited stacks. Because of the
+ greater use of memory management, it runs more slowly. Separate functions are
+ provided so that special-purpose external code can be used for this case. When
+ used, these functions are always called in a stack-like manner (last obtained,
+ first freed), and always for memory blocks of the same size. There is a
+ discussion about PCRE's stack usage in the
+ .\" HREF
+ \fBpcrestack\fP
+ .\"
+ documentation.
+ .P
+ The global variable \fBpcre_callout\fP initially contains NULL. It can be set
  by the caller to a "callout" function, which PCRE will then call at specified
- points during a matching operation. Details are given in the \fBpcrecallout\fR
+ points during a matching operation. Details are given in the
+ .\" HREF
+ \fBpcrecallout\fP
+ .\"
  documentation.
+ .
+ .
+ .\" HTML <a name="newlines"></a>
+ .SH NEWLINES
+ .rs
+ .sp
+ PCRE supports five different conventions for indicating line breaks in
+ strings: a single CR (carriage return) character, a single LF (linefeed)
+ character, the two-character sequence CRLF, any of the three preceding, or any
+ Unicode newline sequence. The Unicode newline sequences are the three just
+ mentioned, plus the single characters VT (vertical tab, U+000B), FF (formfeed,
+ U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
+ (paragraph separator, U+2029).
+ .P
+ Each of the first three conventions is used by at least one operating system as
+ its standard newline sequence. When PCRE is built, a default can be specified.
+ The default default is LF, which is the Unix standard. When PCRE is run, the
+ default can be overridden, either when a pattern is compiled, or when it is
+ matched.
+ .P
+ At compile time, the newline convention can be specified by the \fIoptions\fP
+ argument of \fBpcre_compile()\fP, or it can be specified by special text at the
+ start of the pattern itself; this overrides any other settings. See the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ page for details of the special character sequences.
+ .P
+ In the PCRE documentation the word "newline" is used to mean "the character or
+ pair of characters that indicate a line break". The choice of newline
+ convention affects the handling of the dot, circumflex, and dollar
+ metacharacters, the handling of #-comments in /x mode, and, when CRLF is a
+ recognized line ending sequence, the match position advancement for a
+ non-anchored pattern. There is more detail about this in the
+ .\" HTML <a href="#execoptions">
+ .\" </a>
+ section on \fBpcre_exec()\fP options
+ .\"
+ below.
+ .P
+ The choice of newline convention does not affect the interpretation of
+ the \en or \er escape sequences, nor does it affect what \eR matches, which is
+ controlled in a similar way, but by separate options.
+ .
+ .
  .SH MULTITHREADING
  .rs
  .sp
  The PCRE functions can be used in multi-threading applications, with the
- proviso that the memory management functions pointed to by \fBpcre_malloc\fR
+ proviso that the memory management functions pointed to by \fBpcre_malloc\fP,
- and \fBpcre_free\fR, and the callout function pointed to by \fBpcre_callout\fR,
+ \fBpcre_free\fP, \fBpcre_stack_malloc\fP, and \fBpcre_stack_free\fP, and the
- are shared by all threads.
+ callout function pointed to by \fBpcre_callout\fP, are shared by all threads.
+ .P
  The compiled form of a regular expression is not altered during matching, so
  the same compiled pattern can safely be used by several threads at once.
+ .P
- .SH CHECKING BUILD-TIME OPTIONS
+ If the just-in-time optimization feature is being used, it needs separate
+ memory stack areas for each thread. See the
+ .\" HREF
+ \fBpcrejit\fP
+ .\"
+ documentation for more details.
+ .
+ .
+ .SH "SAVING PRECOMPILED PATTERNS FOR LATER USE"
  .rs
  .sp
- .B int pcre_config(int \fIwhat\fR, void *\fIwhere\fR);
+ The compiled form of a regular expression can be saved and re-used at a later
+ time, possibly by a different program, and even on a host other than the one on
+ which it was compiled. Details are given in the
+ .\" HREF
+ \fBpcreprecompile\fP
+ .\"
+ documentation. However, compiling a regular expression with one version of PCRE
+ for use with a different version is not guaranteed to work and may cause
+ crashes.
+ .
+ .
+ .SH "CHECKING BUILD-TIME OPTIONS"
+ .rs
+ .sp
+ .B int pcre_config(int \fIwhat\fP, void *\fIwhere\fP);
  .PP
- The function \fBpcre_config()\fR makes it possible for a PCRE client to
+ The function \fBpcre_config()\fP makes it possible for a PCRE client to
  discover which optional features have been compiled into the PCRE library. The
  .\" HREF
- \fBpcrebuild\fR
+ \fBpcrebuild\fP
  .\"
  documentation has more details about these optional features.
+ .P
- The first argument for \fBpcre_config()\fR is an integer, specifying which
+ The first argument for \fBpcre_config()\fP is an integer, specifying which
  information is required; the second argument is a pointer to a variable into
  which the information is placed. The following information is available:
+ .sp
    PCRE_CONFIG_UTF8
+ .sp
  The output is an integer that is set to one if UTF-8 support is available;
  otherwise it is set to zero.
+ .sp
+   PCRE_CONFIG_UNICODE_PROPERTIES
+ .sp
+ The output is an integer that is set to one if support for Unicode character
+ properties is available; otherwise it is set to zero.
+ .sp
+   PCRE_CONFIG_JIT
+ .sp
+ The output is an integer that is set to one if support for just-in-time
+ compiling is available; otherwise it is set to zero.
+ .sp
    PCRE_CONFIG_NEWLINE
+ .sp
- The output is an integer that is set to the value of the code that is used for
+ The output is an integer whose value specifies the default character sequence
- the newline character. It is either linefeed (10) or carriage return (13), and
+ that is recognized as meaning "newline". The four values that are supported
- should normally be the standard character for your operating system.
+ are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF, and -1 for ANY.
+ Though they are derived from ASCII, the same values are returned in EBCDIC
+ environments. The default should normally correspond to the standard sequence
+ for your operating system.
+ .sp
+   PCRE_CONFIG_BSR
+ .sp
+ The output is an integer whose value indicates what character sequences the \eR
+ escape sequence matches by default. A value of 0 means that \eR matches any
+ Unicode line ending sequence; a value of 1 means that \eR matches only CR, LF,
+ or CRLF. The default can be overridden when a pattern is compiled or matched.
+ .sp
    PCRE_CONFIG_LINK_SIZE
+ .sp
  The output is an integer that contains the number of bytes used for internal
  linkage in compiled regular expressions. The value is 2, 3, or 4. Larger values
  allow larger regular expressions to be compiled, at the expense of slower
  matching. The default value of 2 is sufficient for all but the most massive
  patterns, since it allows the compiled pattern to be up to 64K in size.
+ .sp
    PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
+ .sp
  The output is an integer that contains the threshold above which the POSIX
- interface uses \fBmalloc()\fR for output vectors. Further details are given in
+ interface uses \fBmalloc()\fP for output vectors. Further details are given in
- the \fBpcreposix\fR documentation.
+ the
+ .\" HREF
+ \fBpcreposix\fP
+ .\"
+ documentation.
+ .sp
    PCRE_CONFIG_MATCH_LIMIT
+ .sp
- The output is an integer that gives the default limit for the number of
+ The output is a long integer that gives the default limit for the number of
- internal matching function calls in a \fBpcre_exec()\fR execution. Further
+ internal matching function calls in a \fBpcre_exec()\fP execution. Further
- details are given with \fBpcre_exec()\fR below.
+ details are given with \fBpcre_exec()\fP below.
+ .sp
- .SH COMPILING A PATTERN
+   PCRE_CONFIG_MATCH_LIMIT_RECURSION
- .rs
+ .sp
- .sp
+ The output is a long integer that gives the default limit for the depth of
- .B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR,
+ recursion when calling the internal matching function in a \fBpcre_exec()\fP
- .ti +5n
+ execution. Further details are given with \fBpcre_exec()\fP below.
- .B const char **\fIerrptr\fR, int *\fIerroffset\fR,
+ .sp
- .ti +5n
+   PCRE_CONFIG_STACKRECURSE
- .B const unsigned char *\fItableptr\fR);
+ .sp
- .PP
+ The output is an integer that is set to one if internal recursion when running
+ \fBpcre_exec()\fP is implemented by recursive function calls that use the stack
- The function \fBpcre_compile()\fR is called to compile a pattern into an
+ to remember their state. This is the usual way that PCRE is compiled. The
- internal form. The pattern is a C string terminated by a binary zero, and
+ output is zero if PCRE was compiled to use blocks of data on the heap instead
- is passed in the argument \fIpattern\fR. A pointer to a single block of memory
+ of recursive function calls. In this case, \fBpcre_stack_malloc\fP and
- that is obtained via \fBpcre_malloc\fR is returned. This contains the compiled
+ \fBpcre_stack_free\fP are called to manage memory blocks on the heap, thus
- code and related data. The \fBpcre\fR type is defined for the returned block;
+ avoiding the use of the stack.
- this is a typedef for a structure whose contents are not externally defined. It
+ .
- is up to the caller to free the memory when it is no longer required.
+ .
+ .SH "COMPILING A PATTERN"
+ .rs
+ .sp
+ .B pcre *pcre_compile(const char *\fIpattern\fP, int \fIoptions\fP,
+ .ti +5n
+ .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
+ .ti +5n
+ .B const unsigned char *\fItableptr\fP);
+ .sp
+ .B pcre *pcre_compile2(const char *\fIpattern\fP, int \fIoptions\fP,
+ .ti +5n
+ .B int *\fIerrorcodeptr\fP,
+ .ti +5n
+ .B const char **\fIerrptr\fP, int *\fIerroffset\fP,
+ .ti +5n
+ .B const unsigned char *\fItableptr\fP);
+ .P
+ Either of the functions \fBpcre_compile()\fP or \fBpcre_compile2()\fP can be
+ called to compile a pattern into an internal form. The only difference between
+ the two interfaces is that \fBpcre_compile2()\fP has an additional argument,
+ \fIerrorcodeptr\fP, via which a numerical error code can be returned. To avoid
+ too much repetition, we refer just to \fBpcre_compile()\fP below, but the
+ information applies equally to \fBpcre_compile2()\fP.
+ .P
+ The pattern is a C string terminated by a binary zero, and is passed in the
+ \fIpattern\fP argument. A pointer to a single block of memory that is obtained
+ via \fBpcre_malloc\fP is returned. This contains the compiled code and related
+ data. The \fBpcre\fP type is defined for the returned block; this is a typedef
+ for a structure whose contents are not externally defined. It is up to the
+ caller to free the memory (via \fBpcre_free\fP) when it is no longer required.
+ .P
  Although the compiled code of a PCRE regex is relocatable, that is, it does not
- depend on memory location, the complete \fBpcre\fR data block is not
+ depend on memory location, the complete \fBpcre\fP data block is not
- fully relocatable, because it contains a copy of the \fItableptr\fR argument,
+ fully relocatable, because it may contain a copy of the \fItableptr\fP
- which is an address (see below).
+ argument, which is an address (see below).
+ .P
- The \fIoptions\fR argument contains independent bits that affect the
+ The \fIoptions\fP argument contains various bit settings that affect the
- compilation. It should be zero if no options are required. Some of the options,
+ compilation. It should be zero if no options are required. The available
- in particular, those that are compatible with Perl, can also be set and unset
+ options are described below. Some of them (in particular, those that are
- from within the pattern (see the detailed description of regular expressions
+ compatible with Perl, but some others as well) can also be set and unset from
- in the \fBpcrepattern\fR documentation). For these options, the contents of the
+ within the pattern (see the detailed description in the
- \fIoptions\fR argument specifies their initial settings at the start of
+ .\" HREF
- compilation and execution. The PCRE_ANCHORED option can be set at the time of
+ \fBpcrepattern\fP
- matching as well as at compile time.
+ .\"
+ documentation). For those options that can be different in different parts of
- If \fIerrptr\fR is NULL, \fBpcre_compile()\fR returns NULL immediately.
+ the pattern, the contents of the \fIoptions\fP argument specifies their
- Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fR returns
+ settings at the start of compilation and execution. The PCRE_ANCHORED,
- NULL, and sets the variable pointed to by \fIerrptr\fR to point to a textual
+ PCRE_BSR_\fIxxx\fP, PCRE_NEWLINE_\fIxxx\fP, PCRE_NO_UTF8_CHECK, and
- error message. The offset from the start of the pattern to the character where
+ PCRE_NO_START_OPT options can be set at the time of matching as well as at
- the error was discovered is placed in the variable pointed to by
+ compile time.
- \fIerroffset\fR, which must not be NULL. If it is, an immediate error is given.
+ .P
+ If \fIerrptr\fP is NULL, \fBpcre_compile()\fP returns NULL immediately.
- If the final argument, \fItableptr\fR, is NULL, PCRE uses a default set of
+ Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fP returns
- character tables which are built when it is compiled, using the default C
+ NULL, and sets the variable pointed to by \fIerrptr\fP to point to a textual
- locale. Otherwise, \fItableptr\fR must be the result of a call to
+ error message. This is a static string that is part of the library. You must
- \fBpcre_maketables()\fR. See the section on locale support below.
+ not try to free it. Normally, the offset from the start of the pattern to the
+ byte that was being processed when the error was discovered is placed in the
- This code fragment shows a typical straightforward call to \fBpcre_compile()\fR:
+ variable pointed to by \fIerroffset\fP, which must not be NULL (if it is, an
+ immediate error is given). However, for an invalid UTF-8 string, the offset is
+ that of the first byte of the failing character. Also, some errors are not
+ detected until checks are carried out when the whole pattern has been scanned;
+ in these cases the offset passed back is the length of the pattern.
+ .P
+ Note that the offset is in bytes, not characters, even in UTF-8 mode. It may
+ sometimes point into the middle of a UTF-8 character.
+ .P
+ If \fBpcre_compile2()\fP is used instead of \fBpcre_compile()\fP, and the
+ \fIerrorcodeptr\fP argument is not NULL, a non-zero error code number is
+ returned via this argument in the event of an error. This is in addition to the
+ textual error message. Error codes and messages are listed below.
+ .P
+ If the final argument, \fItableptr\fP, is NULL, PCRE uses a default set of
+ character tables that are built when PCRE is compiled, using the default C
+ locale. Otherwise, \fItableptr\fP must be an address that is the result of a
+ call to \fBpcre_maketables()\fP. This value is stored with the compiled
+ pattern, and used again by \fBpcre_exec()\fP, unless another table pointer is
+ passed to it. For more discussion, see the section on locale support below.
+ .P
+ This code fragment shows a typical straightforward call to \fBpcre_compile()\fP:
+ .sp
    pcre *re;
    const char *error;
    int erroffset;
-Line 265 
 This code fragment shows a typical strai
+Line 509 
 This code fragment shows a typical strai
      &error,           /* for error message */
      &erroffset,       /* for error offset */
      NULL);            /* use default character tables */
+ .sp
- The following option bits are defined:
+ The following names for option bits are defined in the \fBpcre.h\fP header
+ file:
+ .sp
    PCRE_ANCHORED
+ .sp
  If this bit is set, the pattern is forced to be "anchored", that is, it is
- constrained to match only at the first matching point in the string which is
+ constrained to match only at the first matching point in the string that is
  being searched (the "subject string"). This effect can also be achieved by
  appropriate constructs in the pattern itself, which is the only way to do it in
  Perl.
+ .sp
+   PCRE_AUTO_CALLOUT
+ .sp
+ If this bit is set, \fBpcre_compile()\fP automatically inserts callout items,
+ all with number 255, before each pattern item. For discussion of the callout
+ facility, see the
+ .\" HREF
+ \fBpcrecallout\fP
+ .\"
+ documentation.
+ .sp
+   PCRE_BSR_ANYCRLF
+   PCRE_BSR_UNICODE
+ .sp
+ These options (which are mutually exclusive) control what the \eR escape
+ sequence matches. The choice is either to match only CR, LF, or CRLF, or to
+ match any Unicode newline sequence. The default is specified when PCRE is
+ built. It can be overridden from within the pattern, or by setting an option
+ when a compiled pattern is matched.
+ .sp
    PCRE_CASELESS
+ .sp
  If this bit is set, letters in the pattern match both upper and lower case
  letters. It is equivalent to Perl's /i option, and it can be changed within a
- pattern by a (?i) option setting.
+ pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the
+ concept of case for characters whose values are less than 128, so caseless
+ matching is always possible. For characters with higher values, the concept of
+ case is supported if PCRE is compiled with Unicode property support, but not
+ otherwise. If you want to use caseless matching for characters 128 and above,
+ you must ensure that PCRE is compiled with Unicode property support as well as
+ with UTF-8 support.
+ .sp
    PCRE_DOLLAR_ENDONLY
+ .sp
  If this bit is set, a dollar metacharacter in the pattern matches only at the
  end of the subject string. Without this option, a dollar also matches
- immediately before the final character if it is a newline (but not before any
+ immediately before a newline at the end of the string (but not before any other
- other newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is
+ newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
- set. There is no equivalent to this option in Perl, and no way to set it within
+ There is no equivalent to this option in Perl, and no way to set it within a
- a pattern.
+ pattern.
+ .sp
    PCRE_DOTALL
+ .sp
- If this bit is set, a dot metacharater in the pattern matches all characters,
+ If this bit is set, a dot metacharacter in the pattern matches a character of
- including newlines. Without it, newlines are excluded. This option is
+ any value, including one that indicates a newline. However, it only ever
+ matches one character, even if newlines are coded as CRLF. Without this option,
+ a dot does not match when the current position is at a newline. This option is
  equivalent to Perl's /s option, and it can be changed within a pattern by a
- (?s) option setting. A negative class such as [^a] always matches a newline
+ (?s) option setting. A negative class such as [^a] always matches newline
- character, independent of the setting of this option.
+ characters, independent of the setting of this option.
+ .sp
+   PCRE_DUPNAMES
+ .sp
+ If this bit is set, names used to identify capturing subpatterns need not be
+ unique. This can be helpful for certain types of pattern when it is known that
+ only one instance of the named subpattern can ever be matched. There are more
+ details of named subpatterns below; see also the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ documentation.
+ .sp
    PCRE_EXTENDED
+ .sp
  If this bit is set, whitespace data characters in the pattern are totally
  ignored except when escaped or inside a character class. Whitespace does not
  include the VT character (code 11). In addition, characters between an
- unescaped # outside a character class and the next newline character,
+ unescaped # outside a character class and the next newline, inclusive, are also
- inclusive, are also ignored. This is equivalent to Perl's /x option, and it can
+ ignored. This is equivalent to Perl's /x option, and it can be changed within a
- be changed within a pattern by a (?x) option setting.
+ pattern by a (?x) option setting.
+ .P
+ Which characters are interpreted as newlines is controlled by the options
+ passed to \fBpcre_compile()\fP or by a special sequence at the start of the
+ pattern, as described in the section entitled
+ .\" HTML <a href="pcrepattern.html#newlines">
+ .\" </a>
+ "Newline conventions"
+ .\"
+ in the \fBpcrepattern\fP documentation. Note that the end of this type of
+ comment is a literal newline sequence in the pattern; escape sequences that
+ happen to represent a newline do not count.
+ .P
  This option makes it possible to include comments inside complicated patterns.
  Note, however, that this applies only to data characters. Whitespace characters
  may never appear within special character sequences in a pattern, for example
- within the sequence (?( which introduces a conditional subpattern.
+ within the sequence (?( that introduces a conditional subpattern.
+ .sp
    PCRE_EXTRA
+ .sp
  This option was invented in order to turn on additional functionality of PCRE
  that is incompatible with Perl, but it is currently of very little use. When
  set, any backslash in a pattern that is followed by a letter that has no
  special meaning causes an error, thus reserving these combinations for future
  expansion. By default, as in Perl, a backslash followed by a letter with no
- special meaning is treated as a literal. There are at present no other features
+ special meaning is treated as a literal. (Perl can, however, be persuaded to
- controlled by this option. It can also be set by a (?X) option setting within a
+ give an error for this, by running it with the -w option.) There are at present
- pattern.
+ no other features controlled by this option. It can also be set by a (?X)
+ option setting within a pattern.
+ .sp
+   PCRE_FIRSTLINE
+ .sp
+ If this option is set, an unanchored pattern is required to match before or at
+ the first newline in the subject string, though the matched text may continue
+ over the newline.
+ .sp
+   PCRE_JAVASCRIPT_COMPAT
+ .sp
+ If this option is set, PCRE's behaviour is changed in some ways so that it is
+ compatible with JavaScript rather than Perl. The changes are as follows:
+ .P
+ (1) A lone closing square bracket in a pattern causes a compile-time error,
+ because this is illegal in JavaScript (by default it is treated as a data
+ character). Thus, the pattern AB]CD becomes illegal when this option is set.
+ .P
+ (2) At run time, a back reference to an unset subpattern group matches an empty
+ string (by default this causes the current matching alternative to fail). A
+ pattern such as (\e1)(a) succeeds when this option is set (assuming it can find
+ an "a" in the subject), whereas it fails by default, for Perl compatibility.
+ .sp
    PCRE_MULTILINE
+ .sp
- By default, PCRE treats the subject string as consisting of a single "line" of
+ By default, PCRE treats the subject string as consisting of a single line of
- characters (even if it actually contains several newlines). The "start of line"
+ characters (even if it actually contains newlines). The "start of line"
  metacharacter (^) matches only at the start of the string, while the "end of
  line" metacharacter ($) matches only at the end of the string, or before a
  terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as
  Perl.
+ .P
  When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs
- match immediately following or immediately before any newline in the subject
+ match immediately following or immediately before internal newlines in the
- string, respectively, as well as at the very start and end. This is equivalent
+ subject string, respectively, as well as at the very start and end. This is
- to Perl's /m option, and it can be changed within a pattern by a (?m) option
+ equivalent to Perl's /m option, and it can be changed within a pattern by a
- setting. If there are no "\\n" characters in a subject string, or no
+ (?m) option setting. If there are no newlines in a subject string, or no
  occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
+ .sp
+   PCRE_NEWLINE_CR
+   PCRE_NEWLINE_LF
+   PCRE_NEWLINE_CRLF
+   PCRE_NEWLINE_ANYCRLF
+   PCRE_NEWLINE_ANY
+ .sp
+ These options override the default newline definition that was chosen when PCRE
+ was built. Setting the first or the second specifies that a newline is
+ indicated by a single character (CR or LF, respectively). Setting
+ PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character
+ CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three
+ preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies
+ that any Unicode newline sequence should be recognized. The Unicode newline
+ sequences are the three just mentioned, plus the single characters VT (vertical
+ tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
+ separator, U+2028), and PS (paragraph separator, U+2029). The last two are
+ recognized only in UTF-8 mode.
+ .P
+ The newline setting in the options word uses three bits that are treated
+ as a number, giving eight possibilities. Currently only six are used (default
+ plus the five values above). This means that if you set more than one newline
+ option, the combination may or may not be sensible. For example,
+ PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but
+ other combinations may yield unused numbers and cause an error.
+ .P
+ The only time that a line break in a pattern is specially recognized when
+ compiling is when PCRE_EXTENDED is set. CR and LF are whitespace characters,
+ and so are ignored in this mode. Also, an unescaped # outside a character class
+ indicates a comment that lasts until after the next line break sequence. In
+ other circumstances, line break sequences in patterns are treated as literal
+ data.
+ .P
+ The newline option that is set at compile time becomes the default that is used
+ for \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, but it can be overridden.
+ .sp
    PCRE_NO_AUTO_CAPTURE
+ .sp
  If this option is set, it disables the use of numbered capturing parentheses in
  the pattern. Any opening parenthesis that is not followed by ? behaves as if it
  were followed by ?: but named parentheses can still be used for capturing (and
  they acquire numbers in the usual way). There is no equivalent of this option
  in Perl.
+ .sp
+   NO_START_OPTIMIZE
+ .sp
+ This is an option that acts at matching time; that is, it is really an option
+ for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. If it is set at compile time,
+ it is remembered with the compiled pattern and assumed at matching time. For
+ details see the discussion of PCRE_NO_START_OPTIMIZE
+ .\" HTML <a href="#execoptions">
+ .\" </a>
+ below.
+ .\"
+ .sp
+   PCRE_UCP
+ .sp
+ This option changes the way PCRE processes \eB, \eb, \eD, \ed, \eS, \es, \eW,
+ \ew, and some of the POSIX character classes. By default, only ASCII characters
+ are recognized, but if PCRE_UCP is set, Unicode properties are used instead to
+ classify characters. More details are given in the section on
+ .\" HTML <a href="pcre.html#genericchartypes">
+ .\" </a>
+ generic character types
+ .\"
+ in the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ page. If you set PCRE_UCP, matching one of the items it affects takes much
+ longer. The option is available only if PCRE has been compiled with Unicode
+ property support.
+ .sp
    PCRE_UNGREEDY
+ .sp
  This option inverts the "greediness" of the quantifiers so that they are not
  greedy by default, but become greedy if followed by "?". It is not compatible
  with Perl. It can also be set by a (?U) option setting within the pattern.
+ .sp
    PCRE_UTF8
+ .sp
  This option causes PCRE to regard both the pattern and the subject as strings
  of UTF-8 characters instead of single-byte character strings. However, it is
- available only if PCRE has been built to include UTF-8 support. If not, the use
+ available only when PCRE is built to include UTF-8 support. If not, the use
  of this option provokes an error. Details of how this option changes the
  behaviour of PCRE are given in the
- .\" HTML <a href="pcre.html#utf8support">
+ .\" HREF
+ \fBpcreunicode\fP
+ .\"
+ page.
+ .sp
+   PCRE_NO_UTF8_CHECK
+ .sp
+ When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
+ automatically checked. There is a discussion about the
+ .\" HTML <a href="pcre.html#utf8strings">
  .\" </a>
- section on UTF-8 support
+ validity of UTF-8 strings
  .\"
  in the main
  .\" HREF
- \fBpcre\fR
+ \fBpcre\fP
  .\"
- page.
+ page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_compile()\fP
+ returns an error. If you already know that your pattern is valid, and you want
- .SH STUDYING A PATTERN
+ to skip this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK
+ option. When it is set, the effect of passing an invalid UTF-8 string as a
+ pattern is undefined. It may cause your program to crash. Note that this option
+ can also be passed to \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP, to suppress
+ the UTF-8 validity checking of subject strings.
+ .
+ .
+ .SH "COMPILATION ERROR CODES"
+ .rs
+ .sp
+ The following table lists the error codes than may be returned by
+ \fBpcre_compile2()\fP, along with the error messages that may be returned by
+ both compiling functions. As PCRE has developed, some error codes have fallen
+ out of use. To avoid confusion, they have not been re-used.
+ .sp
+ no error
+ \e at end of pattern
+ \ec at end of pattern
+ unrecognized character follows \e
+ numbers out of order in {} quantifier
+ number too big in {} quantifier
+ missing terminating ] for character class
+ invalid escape sequence in character class
+ range out of order in character class
+ nothing to repeat
+ [this code is not in use]
+ internal error: unexpected repeat
+ unrecognized character after (? or (?-
+ POSIX named classes are supported only within a class
+ missing )
+ reference to non-existent subpattern
+ erroffset passed as NULL
+ unknown option bit(s) set
+ missing ) after comment
+ [this code is not in use]
+ regular expression is too large
+ failed to get memory
+ unmatched parentheses
+ internal error: code overflow
+ unrecognized character after (?<
+ lookbehind assertion is not fixed length
+ malformed number or name after (?(
+ conditional group contains more than two branches
+ assertion expected after (?(
+ (?R or (?[+-]digits must be followed by )
+ unknown POSIX class name
+ POSIX collating elements are not supported
+ this version of PCRE is not compiled with PCRE_UTF8 support
+ [this code is not in use]
+ character value in \ex{...} sequence is too large
+ invalid condition (?(0)
+ \eC not allowed in lookbehind assertion
+ PCRE does not support \eL, \el, \eN{name}, \eU, or \eu
+ number after (?C is > 255
+ closing ) for (?C expected
+ recursive call could loop indefinitely
+ unrecognized character after (?P
+ syntax error in subpattern name (missing terminator)
+ two named subpatterns have the same name
+ invalid UTF-8 string
+ support for \eP, \ep, and \eX has not been compiled
+ malformed \eP or \ep sequence
+ unknown property name after \eP or \ep
+ subpattern name is too long (maximum 32 characters)
+ too many named subpatterns (maximum 10000)
+ [this code is not in use]
+ octal value is greater than \e377 (not in UTF-8 mode)
+ internal error: overran compiling workspace
+ internal error: previously-checked referenced subpattern
+         not found
+ DEFINE group contains more than one branch
+ repeating a DEFINE group is not allowed
+ inconsistent NEWLINE options
+ \eg is not followed by a braced, angle-bracketed, or quoted
+         name/number or by a plain number
+ a numbered reference must not be zero
+ an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
+ (*VERB) not recognized
+ number is too big
+ subpattern name expected
+ digit expected after (?+
+ ] is an invalid data character in JavaScript compatibility mode
+ different names for subpatterns of the same number are
+         not allowed
+ (*MARK) must have an argument
+ this version of PCRE is not compiled with PCRE_UCP support
+ \ec must be followed by an ASCII character
+ \ek is not followed by a braced, angle-bracketed, or quoted name
+ .sp
+ The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may
+ be used if the limits were changed when PCRE was built.
+ .
+ .
+ .\" HTML <a name="studyingapattern"></a>
+ .SH "STUDYING A PATTERN"
  .rs
  .sp
- .B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR,
+ .B pcre_extra *pcre_study(const pcre *\fIcode\fP, int \fIoptions\fP
  .ti +5n
- .B const char **\fIerrptr\fR);
+ .B const char **\fIerrptr\fP);
  .PP
- When a pattern is going to be used several times, it is worth spending more
+ If a compiled pattern is going to be used several times, it is worth spending
- time analyzing it in order to speed up the time taken for matching. The
+ more time analyzing it in order to speed up the time taken for matching. The
- function \fBpcre_study()\fR takes a pointer to a compiled pattern as its first
+ function \fBpcre_study()\fP takes a pointer to a compiled pattern as its first
- argument. If studing the pattern produces additional information that will help
+ argument. If studying the pattern produces additional information that will
- speed up matching, \fBpcre_study()\fR returns a pointer to a \fBpcre_extra\fR
+ help speed up matching, \fBpcre_study()\fP returns a pointer to a
- block, in which the \fIstudy_data\fR field points to the results of the study.
+ \fBpcre_extra\fP block, in which the \fIstudy_data\fP field points to the
+ results of the study.
- The returned value from a \fBpcre_study()\fR can be passed directly to
+ .P
- \fBpcre_exec()\fR. However, the \fBpcre_extra\fR block also contains other
+ The returned value from \fBpcre_study()\fP can be passed directly to
- fields that can be set by the caller before the block is passed; these are
+ \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP. However, a \fBpcre_extra\fP block
- described below. If studying the pattern does not produce any additional
+ also contains other fields that can be set by the caller before the block is
- information, \fBpcre_study()\fR returns NULL. In that circumstance, if the
+ passed; these are described
- calling program wants to pass some of the other fields to \fBpcre_exec()\fR, it
+ .\" HTML <a href="#extradata">
- must set up its own \fBpcre_extra\fR block.
+ .\" </a>
+ below
- The second argument contains option bits. At present, no options are defined
+ .\"
- for \fBpcre_study()\fR, and this argument should always be zero.
+ in the section on matching a pattern.
+ .P
- The third argument for \fBpcre_study()\fR is a pointer for an error message. If
+ If studying the pattern does not produce any useful information,
+ \fBpcre_study()\fP returns NULL. In that circumstance, if the calling program
+ wants to pass any of the other fields to \fBpcre_exec()\fP or
+ \fBpcre_dfa_exec()\fP, it must set up its own \fBpcre_extra\fP block.
+ .P
+ The second argument of \fBpcre_study()\fP contains option bits. There is only
+ one option: PCRE_STUDY_JIT_COMPILE. If this is set, and the just-in-time
+ compiler is available, the pattern is further compiled into machine code that
+ executes much faster than the \fBpcre_exec()\fP matching function. If
+ the just-in-time compiler is not available, this option is ignored. All other
+ bits in the \fIoptions\fP argument must be zero.
+ .P
+ JIT compilation is a heavyweight optimization. It can take some time for
+ patterns to be analyzed, and for one-off matches and simple patterns the
+ benefit of faster execution might be offset by a much slower study time.
+ Not all patterns can be optimized by the JIT compiler. For those that cannot be
+ handled, matching automatically falls back to the \fBpcre_exec()\fP
+ interpreter. For more details, see the
+ .\" HREF
+ \fBpcrejit\fP
+ .\"
+ documentation.
+ .P
+ The third argument for \fBpcre_study()\fP is a pointer for an error message. If
  studying succeeds (even if no data is returned), the variable it points to is
- set to NULL. Otherwise it points to a textual error message. You should
+ set to NULL. Otherwise it is set to point to a textual error message. This is a
- therefore test the error pointer for NULL after calling \fBpcre_study()\fR, to
+ static string that is part of the library. You must not try to free it. You
- be sure that it has run successfully.
+ should test the error pointer for NULL after calling \fBpcre_study()\fP, to be
+ sure that it has run successfully.
- This is a typical call to \fBpcre_study\fR():
+ .P
+ When you are finished with a pattern, you can free the memory used for the
-   pcre_extra *pe;
+ study data by calling \fBpcre_free_study()\fP. This function was added to the
-   pe = pcre_study(
+ API for release 8.20. For earlier versions, the memory could be freed with
+ \fBpcre_free()\fP, just like the pattern itself. This will still work in cases
+ where PCRE_STUDY_JIT_COMPILE is not used, but it is advisable to change to the
+ new function when convenient.
+ .P
+ This is a typical way in which \fBpcre_study\fP() is used (except that in a
+ real application there should be tests for errors):
+ .sp
+   int rc;
+   pcre *re;
+   pcre_extra *sd;
+   re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
+   sd = pcre_study(
      re,             /* result of pcre_compile() */
-,              /* no options exist */
+,              /* no options */
      &error);        /* set to NULL or points to a message */
+   rc = pcre_exec(   /* see below for details of pcre_exec() options */
- At present, studying a pattern is useful only for non-anchored patterns that do
+     re, sd, "subject", 7, 0, 0, ovector, 30);
- not have a single fixed starting character. A bitmap of possible starting
+   ...
- characters is created.
+   pcre_free_study(sd);
+   pcre_free(re);
+ .sp
+ Studying a pattern does two things: first, a lower bound for the length of
+ subject string that is needed to match the pattern is computed. This does not
+ mean that there are any strings of that length that match, but it does
+ guarantee that no shorter strings match. The value is used by
+ \fBpcre_exec()\fP and \fBpcre_dfa_exec()\fP to avoid wasting time by trying to
+ match strings that are shorter than the lower bound. You can find out the value
+ in a calling program via the \fBpcre_fullinfo()\fP function.
+ .P
+ Studying a pattern is also useful for non-anchored patterns that do not have a
+ single fixed starting character. A bitmap of possible starting bytes is
+ created. This speeds up finding a position in the subject at which to start
+ matching.
+ .P
+ These two optimizations apply to both \fBpcre_exec()\fP and
+ \fBpcre_dfa_exec()\fP. However, they are not used by \fBpcre_exec()\fP if
+ \fBpcre_study()\fP is called with the PCRE_STUDY_JIT_COMPILE option, and
+ just-in-time compiling is successful. The optimizations can be disabled by
+ setting the PCRE_NO_START_OPTIMIZE option when calling \fBpcre_exec()\fP or
+ \fBpcre_dfa_exec()\fP. You might want to do this if your pattern contains
+ callouts or (*MARK) (which cannot be handled by the JIT compiler), and you want
+ to make use of these facilities in cases where matching fails. See the
+ discussion of PCRE_NO_START_OPTIMIZE
+ .\" HTML <a href="#execoptions">
+ .\" </a>
+ below.
+ .\"
+ .
+ .
  .\" HTML <a name="localesupport"></a>
- .SH LOCALE SUPPORT
+ .SH "LOCALE SUPPORT"
  .rs
  .sp
  PCRE handles caseless matching, and determines whether characters are letters,
- digits, or whatever, by reference to a set of tables. When running in UTF-8
+ digits, or whatever, by reference to a set of tables, indexed by character
- mode, this applies only to characters with codes less than 256. The library
+ value. When running in UTF-8 mode, this applies only to characters with codes
- contains a default set of tables that is created in the default C locale when
+ less than 128. By default, higher-valued codes never match escapes such as \ew
- PCRE is compiled. This is used when the final argument of \fBpcre_compile()\fR
+ or \ed, but they can be tested with \ep if PCRE is built with Unicode character
- is NULL, and is sufficient for many applications.
+ property support. Alternatively, the PCRE_UCP option can be set at compile
+ time; this causes \ew and friends to use Unicode property support instead of
- An alternative set of tables can, however, be supplied. Such tables are built
+ built-in tables. The use of locales with Unicode is discouraged. If you are
- by calling the \fBpcre_maketables()\fR function, which has no arguments, in the
+ handling characters with codes greater than 128, you should either use UTF-8
- relevant locale. The result can then be passed to \fBpcre_compile()\fR as often
+ and Unicode, or use locales, but not try to mix the two.
- as necessary. For example, to build and use tables that are appropriate for the
+ .P
- French locale (where accented characters with codes greater than 128 are
+ PCRE contains an internal set of tables that are used when the final argument
- treated as letters), the following code could be used:
+ of \fBpcre_compile()\fP is NULL. These are sufficient for many applications.
+ Normally, the internal tables recognize only ASCII characters. However, when
-   setlocale(LC_CTYPE, "fr");
+ PCRE is built, it is possible to cause the internal tables to be rebuilt in the
+ default "C" locale of the local system, which may cause them to be different.
+ .P
+ The internal tables can always be overridden by tables supplied by the
+ application that calls PCRE. These may be created in a different locale from
+ the default. As more and more applications change to using Unicode, the need
+ for this locale support is expected to die away.
+ .P
+ External tables are built by calling the \fBpcre_maketables()\fP function,
+ which has no arguments, in the relevant locale. The result can then be passed
+ to \fBpcre_compile()\fP or \fBpcre_exec()\fP as often as necessary. For
+ example, to build and use tables that are appropriate for the French locale
+ (where accented characters with values greater than 128 are treated as letters),
+ the following code could be used:
+ .sp
+   setlocale(LC_CTYPE, "fr_FR");
    tables = pcre_maketables();
    re = pcre_compile(..., tables);
+ .sp
- The tables are built in memory that is obtained via \fBpcre_malloc\fR. The
+ The locale name "fr_FR" is used on Linux and other Unix-like systems; if you
- pointer that is passed to \fBpcre_compile\fR is saved with the compiled
+ are using Windows, the name for the French locale is "french".
- pattern, and the same tables are used via this pointer by \fBpcre_study()\fR
+ .P
- and \fBpcre_exec()\fR. Thus, for any single pattern, compilation, studying and
+ When \fBpcre_maketables()\fP runs, the tables are built in memory that is
- matching all happen in the same locale, but different patterns can be compiled
+ obtained via \fBpcre_malloc\fP. It is the caller's responsibility to ensure
- in different locales. It is the caller's responsibility to ensure that the
+ that the memory containing the tables remains available for as long as it is
- memory containing the tables remains available for as long as it is needed.
+ needed.
+ .P
- .SH INFORMATION ABOUT A PATTERN
+ The pointer that is passed to \fBpcre_compile()\fP is saved with the compiled
+ pattern, and the same tables are used via this pointer by \fBpcre_study()\fP
+ and normally also by \fBpcre_exec()\fP. Thus, by default, for any single
+ pattern, compilation, studying and matching all happen in the same locale, but
+ different patterns can be compiled in different locales.
+ .P
+ It is possible to pass a table pointer or NULL (indicating the use of the
+ internal tables) to \fBpcre_exec()\fP. Although not intended for this purpose,
+ this facility could be used to match a pattern in a different locale from the
+ one in which it was compiled. Passing table pointers at run time is discussed
+ below in the section on matching a pattern.
+ .
+ .
+ .\" HTML <a name="infoaboutpattern"></a>
+ .SH "INFORMATION ABOUT A PATTERN"
  .rs
  .sp
- .B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"
+ .B int pcre_fullinfo(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
  .ti +5n
- .B int \fIwhat\fR, void *\fIwhere\fR);
+ .B int \fIwhat\fP, void *\fIwhere\fP);
  .PP
- The \fBpcre_fullinfo()\fR function returns information about a compiled
+ The \fBpcre_fullinfo()\fP function returns information about a compiled
- pattern. It replaces the obsolete \fBpcre_info()\fR function, which is
+ pattern. It replaces the obsolete \fBpcre_info()\fP function, which is
  nevertheless retained for backwards compability (and is documented below).
+ .P
- The first argument for \fBpcre_fullinfo()\fR is a pointer to the compiled
+ The first argument for \fBpcre_fullinfo()\fP is a pointer to the compiled
- pattern. The second argument is the result of \fBpcre_study()\fR, or NULL if
+ pattern. The second argument is the result of \fBpcre_study()\fP, or NULL if
  the pattern was not studied. The third argument specifies which piece of
  information is required, and the fourth argument is a pointer to a variable
  to receive the data. The yield of the function is zero for success, or one of
  the following negative numbers:
+ .sp
-   PCRE_ERROR_NULL       the argument \fIcode\fR was NULL
+   PCRE_ERROR_NULL       the argument \fIcode\fP was NULL
-                         the argument \fIwhere\fR was NULL
+                         the argument \fIwhere\fP was NULL
    PCRE_ERROR_BADMAGIC   the "magic number" was not found
-   PCRE_ERROR_BADOPTION  the value of \fIwhat\fR was invalid
+   PCRE_ERROR_BADOPTION  the value of \fIwhat\fP was invalid
+ .sp
- Here is a typical call of \fBpcre_fullinfo()\fR, to obtain the length of the
+ The "magic number" is placed at the start of each compiled pattern as an simple
- compiled pattern:
+ check against passing an arbitrary memory pointer. Here is a typical call of
+ \fBpcre_fullinfo()\fP, to obtain the length of the compiled pattern:
+ .sp
    int rc;
-   unsigned long int length;
+   size_t length;
    rc = pcre_fullinfo(
      re,               /* result of pcre_compile() */
-     pe,               /* result of pcre_study(), or NULL */
+     sd,               /* result of pcre_study(), or NULL */
      PCRE_INFO_SIZE,   /* what is required */
      &length);         /* where to put the data */
+ .sp
- The possible values for the third argument are defined in \fBpcre.h\fR, and are
+ The possible values for the third argument are defined in \fBpcre.h\fP, and are
  as follows:
+ .sp
    PCRE_INFO_BACKREFMAX
+ .sp
  Return the number of the highest back reference in the pattern. The fourth
- argument should point to an \fBint\fR variable. Zero is returned if there are
+ argument should point to an \fBint\fP variable. Zero is returned if there are
  no back references.
+ .sp
    PCRE_INFO_CAPTURECOUNT
+ .sp
  Return the number of capturing subpatterns in the pattern. The fourth argument
- should point to an \fbint\fR variable.
+ should point to an \fBint\fP variable.
+ .sp
+   PCRE_INFO_DEFAULT_TABLES
+ .sp
+ Return a pointer to the internal default character tables within PCRE. The
+ fourth argument should point to an \fBunsigned char *\fP variable. This
+ information call is provided for internal use by the \fBpcre_study()\fP
+ function. External callers can cause PCRE to use its internal tables by passing
+ a NULL table pointer.
+ .sp
    PCRE_INFO_FIRSTBYTE
+ .sp
  Return information about the first byte of any matched string, for a
- non-anchored pattern. (This option used to be called PCRE_INFO_FIRSTCHAR; the
+ non-anchored pattern. The fourth argument should point to an \fBint\fP
- old name is still recognized for backwards compatibility.)
+ variable. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name is
+ still recognized for backwards compatibility.)
- If there is a fixed first byte, e.g. from a pattern such as (cat|cow|coyote),
+ .P
- it is returned in the integer pointed to by \fIwhere\fR. Otherwise, if either
+ If there is a fixed first byte, for example, from a pattern such as
+ (cat|cow|coyote), its value is returned. Otherwise, if either
+ .sp
  (a) the pattern was compiled with the PCRE_MULTILINE option, and every branch
  starts with "^", or
+ .sp
  (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set
  (if it were set, the pattern would be anchored),
+ .sp
  -1 is returned, indicating that the pattern matches only at the start of a
  subject string or after any newline within the string. Otherwise -2 is
  returned. For anchored patterns, -2 is returned.
+ .sp
    PCRE_INFO_FIRSTTABLE
+ .sp
  If the pattern was studied, and this resulted in the construction of a 256-bit
  table indicating a fixed set of bytes for the first byte in any matching
  string, a pointer to the table is returned. Otherwise NULL is returned. The
- fourth argument should point to an \fBunsigned char *\fR variable.
+ fourth argument should point to an \fBunsigned char *\fP variable.
+ .sp
+   PCRE_INFO_HASCRORLF
+ .sp
+ Return 1 if the pattern contains any explicit matches for CR or LF characters,
+ otherwise 0. The fourth argument should point to an \fBint\fP variable. An
+ explicit match is either a literal CR or LF character, or \er or \en.
+ .sp
+   PCRE_INFO_JCHANGED
+ .sp
+ Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise
+. The fourth argument should point to an \fBint\fP variable. (?J) and
+ (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
+ .sp
+   PCRE_INFO_JIT
+ .sp
+ Return 1 if the pattern was studied with the PCRE_STUDY_JIT_COMPILE option, and
+ just-in-time compiling was successful. The fourth argument should point to an
+ \fBint\fP variable. A return value of 0 means that JIT support is not available
+ in this version of PCRE, or that the pattern was not studied with the
+ PCRE_STUDY_JIT_COMPILE option, or that the JIT compiler could not handle this
+ particular pattern. See the
+ .\" HREF
+ \fBpcrejit\fP
+ .\"
+ documentation for details of what can and cannot be handled.
+ .sp
    PCRE_INFO_LASTLITERAL
+ .sp
- For a non-anchored pattern, return the value of the rightmost literal byte
+ Return the value of the rightmost literal byte that must exist in any matched
- which must exist in any matched string, other than at its start. The fourth
+ string, other than at its start, if such a byte has been recorded. The fourth
- argument should point to an \fBint\fR variable. If there is no such byte, or if
+ argument should point to an \fBint\fP variable. If there is no such byte, -1 is
- the pattern is anchored, -1 is returned. For example, for the pattern
+ returned. For anchored patterns, a last literal byte is recorded only if it
- /a\\d+z\\d+/ the returned value is 'z'.
+ follows something of variable length. For example, for the pattern
+ /^a\ed+z\ed+/ the returned value is "z", but for /^a\edz\ed/ the returned value
+ is -1.
+ .sp
+   PCRE_INFO_MINLENGTH
+ .sp
+ If the pattern was studied and a minimum length for matching subject strings
+ was computed, its value is returned. Otherwise the returned value is -1. The
+ value is a number of characters, not bytes (this may be relevant in UTF-8
+ mode). The fourth argument should point to an \fBint\fP variable. A
+ non-negative value is a lower bound to the length of any matching string. There
+ may not be any strings of that length that do actually match, but every string
+ that does match is at least that long.
+ .sp
    PCRE_INFO_NAMECOUNT
    PCRE_INFO_NAMEENTRYSIZE
    PCRE_INFO_NAMETABLE
+ .sp
  PCRE supports the use of named as well as numbered capturing parentheses. The
  names are just an additional way of identifying the parentheses, which still
- acquire a number. A caller that wants to extract data from a named subpattern
+ acquire numbers. Several convenience functions such as
- must convert the name to a number in order to access the correct pointers in
+ \fBpcre_get_named_substring()\fP are provided for extracting captured
- the output vector (described with \fBpcre_exec()\fR below). In order to do
+ substrings by name. It is also possible to extract the data directly, by first
- this, it must first use these three values to obtain the name-to-number mapping
+ converting the name to a number in order to access the correct pointers in the
- table for the pattern.
+ output vector (described with \fBpcre_exec()\fP below). To do the conversion,
+ you need to use the name-to-number map, which is described by these three
+ values.
+ .P
  The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives
  the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each
- entry; both of these return an \fBint\fR value. The entry size depends on the
+ entry; both of these return an \fBint\fP value. The entry size depends on the
  length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first
- entry of the table (a pointer to \fBchar\fR). The first two bytes of each entry
+ entry of the table (a pointer to \fBchar\fP). The first two bytes of each entry
  are the number of the capturing parenthesis, most significant byte first. The
- rest of the entry is the corresponding name, zero terminated. The names are in
+ rest of the entry is the corresponding name, zero terminated.
- alphabetical order. For example, consider the following pattern (assume
+ .P
- PCRE_EXTENDED is set, so white space - including newlines - is ignored):
+ The names are in alphabetical order. Duplicate names may appear if (?| is used
+ to create multiple groups with the same number, as described in the
-   (?P<date> (?P<year>(\\d\\d)?\\d\\d) -
+ .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
-   (?P<month>\\d\\d) - (?P<day>\\d\\d) )
+ .\" </a>
+ section on duplicate subpattern numbers
+ .\"
+ in the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ page. Duplicate names for subpatterns with different numbers are permitted only
+ if PCRE_DUPNAMES is set. In all cases of duplicate names, they appear in the
+ table in the order in which they were found in the pattern. In the absence of
+ (?| this is the order of increasing number; when (?| is used this is not
+ necessarily the case because later subpatterns may have lower numbers.
+ .P
+ As a simple example of the name/number table, consider the following pattern
+ (assume PCRE_EXTENDED is set, so white space - including newlines - is
+ ignored):
+ .sp
+ .\" JOIN
+   (?<date> (?<year>(\ed\ed)?\ed\ed) -
+   (?<month>\ed\ed) - (?<day>\ed\ed) )
+ .sp
  There are four named subpatterns, so the table has four entries, and each entry
  in the table is eight bytes long. The table is as follows, with non-printing
- bytes shows in hex, and undefined bytes shown as ??:
+ bytes shows in hexadecimal, and undefined bytes shown as ??:
+ .sp
 01 d  a  t  e  00 ??
 05 d  a  y  00 ?? ??
 04 m  o  n  t  h  00
 02 y  e  a  r  00 ??
+ .sp
- When writing code to extract data from named subpatterns, remember that the
+ When writing code to extract data from named subpatterns using the
- length of each entry may be different for each compiled pattern.
+ name-to-number map, remember that the length of the entries is likely to be
+ different for each compiled pattern.
+ .sp
+   PCRE_INFO_OKPARTIAL
+ .sp
+ Return 1 if the pattern can be used for partial matching with
+ \fBpcre_exec()\fP, otherwise 0. The fourth argument should point to an
+ \fBint\fP variable. From release 8.00, this always returns 1, because the
+ restrictions that previously applied to partial matching have been lifted. The
+ .\" HREF
+ \fBpcrepartial\fP
+ .\"
+ documentation gives details of partial matching.
+ .sp
    PCRE_INFO_OPTIONS
+ .sp
  Return a copy of the options with which the pattern was compiled. The fourth
- argument should point to an \fBunsigned long int\fR variable. These option bits
+ argument should point to an \fBunsigned long int\fP variable. These option bits
- are those specified in the call to \fBpcre_compile()\fR, modified by any
+ are those specified in the call to \fBpcre_compile()\fP, modified by any
- top-level option settings within the pattern itself.
+ top-level option settings at the start of the pattern itself. In other words,
+ they are the options that will be in force when matching starts. For example,
+ if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the
+ result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED.
+ .P
  A pattern is automatically anchored by PCRE if all of its top-level
  alternatives begin with one of the following:
+ .sp
    ^     unless PCRE_MULTILINE is set
-   \\A    always
+   \eA    always
-   \\G    always
+   \eG    always
+ .\" JOIN
    .*    if PCRE_DOTALL is set and there are no back
            references to the subpattern in which .* appears
+ .sp
  For such patterns, the PCRE_ANCHORED bit is set in the options returned by
- \fBpcre_fullinfo()\fR.
+ \fBpcre_fullinfo()\fP.
+ .sp
    PCRE_INFO_SIZE
+ .sp
  Return the size of the compiled pattern, that is, the value that was passed as
- the argument to \fBpcre_malloc()\fR when PCRE was getting memory in which to
+ the argument to \fBpcre_malloc()\fP when PCRE was getting memory in which to
- place the compiled data. The fourth argument should point to a \fBsize_t\fR
+ place the compiled data. The fourth argument should point to a \fBsize_t\fP
  variable.
+ .sp
    PCRE_INFO_STUDYSIZE
+ .sp
- Returns the size of the data block pointed to by the \fIstudy_data\fR field in
+ Return the size of the data block pointed to by the \fIstudy_data\fP field in a
- a \fBpcre_extra\fR block. That is, it is the value that was passed to
+ \fBpcre_extra\fP block. If \fBpcre_extra\fP is NULL, or there is no study data,
- \fBpcre_malloc()\fR when PCRE was getting memory into which to place the data
+ zero is returned. The fourth argument should point to a \fBsize_t\fP variable.
- created by \fBpcre_study()\fR. The fourth argument should point to a
+ The \fIstudy_data\fP field is set by \fBpcre_study()\fP to record information
- \fBsize_t\fR variable.
+ that will speed up matching (see the section entitled
+ .\" HTML <a href="#studyingapattern">
- .SH OBSOLETE INFO FUNCTION
+ .\" </a>
+ "Studying a pattern"
+ .\"
+ above). The format of the \fIstudy_data\fP block is private, but its length
+ is made available via this option so that it can be saved and restored (see the
+ .\" HREF
+ \fBpcreprecompile\fP
+ .\"
+ documentation for details).
+ .
+ .
+ .SH "OBSOLETE INFO FUNCTION"
  .rs
  .sp
- .B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int
+ .B int pcre_info(const pcre *\fIcode\fP, int *\fIoptptr\fP, int
- .B *\fIfirstcharptr\fR);
+ .B *\fIfirstcharptr\fP);
  .PP
- The \fBpcre_info()\fR function is now obsolete because its interface is too
+ The \fBpcre_info()\fP function is now obsolete because its interface is too
  restrictive to return all the available data about a compiled pattern. New
- programs should use \fBpcre_fullinfo()\fR instead. The yield of
+ programs should use \fBpcre_fullinfo()\fP instead. The yield of
- \fBpcre_info()\fR is the number of capturing subpatterns, or one of the
+ \fBpcre_info()\fP is the number of capturing subpatterns, or one of the
  following negative numbers:
+ .sp
-   PCRE_ERROR_NULL       the argument \fIcode\fR was NULL
+   PCRE_ERROR_NULL       the argument \fIcode\fP was NULL
    PCRE_ERROR_BADMAGIC   the "magic number" was not found
+ .sp
- If the \fIoptptr\fR argument is not NULL, a copy of the options with which the
+ If the \fIoptptr\fP argument is not NULL, a copy of the options with which the
  pattern was compiled is placed in the integer it points to (see
  PCRE_INFO_OPTIONS above).
+ .P
- If the pattern is not anchored and the \fIfirstcharptr\fR argument is not NULL,
+ If the pattern is not anchored and the \fIfirstcharptr\fP argument is not NULL,
  it is used to pass back information about the first character of any matched
  string (see PCRE_INFO_FIRSTBYTE above).
+ .
- .SH MATCHING A PATTERN
+ .
+ .SH "REFERENCE COUNTS"
+ .rs
+ .sp
+ .B int pcre_refcount(pcre *\fIcode\fP, int \fIadjust\fP);
+ .PP
+ The \fBpcre_refcount()\fP function is used to maintain a reference count in the
+ data block that contains a compiled pattern. It is provided for the benefit of
+ applications that operate in an object-oriented manner, where different parts
+ of the application may be using the same compiled pattern, but you want to free
+ the block when they are all done.
+ .P
+ When a pattern is compiled, the reference count field is initialized to zero.
+ It is changed only by calling this function, whose action is to add the
+ \fIadjust\fP value (which may be positive or negative) to it. The yield of the
+ function is the new value. However, the value of the count is constrained to
+ lie between 0 and 65535, inclusive. If the new value is outside these limits,
+ it is forced to the appropriate limit value.
+ .P
+ Except when it is zero, the reference count is not correctly preserved if a
+ pattern is compiled on one host and then transferred to a host whose byte-order
+ is different. (This seems a highly unlikely scenario.)
+ .
+ .
+ .SH "MATCHING A PATTERN: THE TRADITIONAL FUNCTION"
  .rs
  .sp
- .B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR,"
+ .B int pcre_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
  .ti +5n
- .B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR,
+ .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
  .ti +5n
- .B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR);
+ .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP);
- .PP
+ .P
- The function \fBpcre_exec()\fR is called to match a subject string against a
+ The function \fBpcre_exec()\fP is called to match a subject string against a
- pre-compiled pattern, which is passed in the \fIcode\fR argument. If the
+ compiled pattern, which is passed in the \fIcode\fP argument. If the
- pattern has been studied, the result of the study should be passed in the
+ pattern was studied, the result of the study should be passed in the
- \fIextra\fR argument.
+ \fIextra\fP argument. This function is the main matching facility of the
+ library, and it operates in a Perl-like manner. For specialist use there is
- Here is an example of a simple call to \fBpcre_exec()\fR:
+ also an alternative matching function, which is described
+ .\" HTML <a href="#dfamatch">
+ .\" </a>
+ below
+ .\"
+ in the section about the \fBpcre_dfa_exec()\fP function.
+ .P
+ In most applications, the pattern will have been compiled (and optionally
+ studied) in the same process that calls \fBpcre_exec()\fP. However, it is
+ possible to save compiled patterns and study data, and then use them later
+ in different processes, possibly even on different hosts. For a discussion
+ about this, see the
+ .\" HREF
+ \fBpcreprecompile\fP
+ .\"
+ documentation.
+ .P
+ Here is an example of a simple call to \fBpcre_exec()\fP:
+ .sp
    int rc;
    int ovector[30];
    rc = pcre_exec(
-Line 645 
 Here is an example of a simple call to \
+Line 1356 
 Here is an example of a simple call to \
 ,             /* the length of the subject string */
 ,              /* start at offset 0 in the subject */
 ,              /* default options */
-     ovector,        /* vector for substring information */
+     ovector,        /* vector of integers for substring information */
-);            /* number of elements in the vector */
+);            /* number of elements (NOT size in bytes) */
+ .
- If the \fIextra\fR argument is not NULL, it must point to a \fBpcre_extra\fR
+ .
- data block. The \fBpcre_study()\fR function returns such a block (when it
+ .\" HTML <a name="extradata"></a>
+ .SS "Extra data for \fBpcre_exec()\fR"
+ .rs
+ .sp
+ If the \fIextra\fP argument is not NULL, it must point to a \fBpcre_extra\fP
+ data block. The \fBpcre_study()\fP function returns such a block (when it
  doesn't return NULL), but you can also create one for yourself, and pass
- additional information in it. The fields in the block are as follows:
+ additional information in it. The \fBpcre_extra\fP block contains the following
+ fields (not necessarily in this order):
-   unsigned long int \fIflags\fR;
+ .sp
-   void *\fIstudy_data\fR;
+   unsigned long int \fIflags\fP;
-   unsigned long int \fImatch_limit\fR;
+   void *\fIstudy_data\fP;
-   void *\fIcallout_data\fR;
+   void *\fIexecutable_jit\fP;
+   unsigned long int \fImatch_limit\fP;
- The \fIflags\fR field is a bitmap that specifies which of the other fields
+   unsigned long int \fImatch_limit_recursion\fP;
+   void *\fIcallout_data\fP;
+   const unsigned char *\fItables\fP;
+   unsigned char **\fImark\fP;
+ .sp
+ The \fIflags\fP field is a bitmap that specifies which of the other fields
  are set. The flag bits are:
+ .sp
    PCRE_EXTRA_STUDY_DATA
+   PCRE_EXTRA_EXECUTABLE_JIT
    PCRE_EXTRA_MATCH_LIMIT
+   PCRE_EXTRA_MATCH_LIMIT_RECURSION
    PCRE_EXTRA_CALLOUT_DATA
+   PCRE_EXTRA_TABLES
- Other flag bits should be set to zero. The \fIstudy_data\fR field is set in the
+   PCRE_EXTRA_MARK
- \fBpcre_extra\fR block that is returned by \fBpcre_study()\fR, together with
+ .sp
- the appropriate flag bit. You should not set this yourself, but you can add to
+ Other flag bits should be set to zero. The \fIstudy_data\fP field and sometimes
- the block by setting the other fields.
+ the \fIexecutable_jit\fP field are set in the \fBpcre_extra\fP block that is
+ returned by \fBpcre_study()\fP, together with the appropriate flag bits. You
- The \fImatch_limit\fR field provides a means of preventing PCRE from using up a
+ should not set these yourself, but you may add to the block by setting the
+ other fields and their corresponding flag bits.
+ .P
+ The \fImatch_limit\fP field provides a means of preventing PCRE from using up a
  vast amount of resources when running patterns that are not going to match,
  but which have a very large number of possibilities in their search trees. The
- classic example is the use of nested unlimited repeats. Internally, PCRE uses a
+ classic example is a pattern that uses nested unlimited repeats.
- function called \fBmatch()\fR which it calls repeatedly (sometimes
+ .P
- recursively). The limit is imposed on the number of times this function is
+ Internally, \fBpcre_exec()\fP uses a function called \fBmatch()\fP, which it
- called during a match, which has the effect of limiting the amount of recursion
+ calls repeatedly (sometimes recursively). The limit set by \fImatch_limit\fP is
- and backtracking that can take place. For patterns that are not anchored, the
+ imposed on the number of times this function is called during a match, which
- count starts from zero for each position in the subject string.
+ has the effect of limiting the amount of backtracking that can take place. For
+ patterns that are not anchored, the count restarts from zero for each position
- The default limit for the library can be set when PCRE is built; the default
+ in the subject string.
+ .P
+ When \fBpcre_exec()\fP is called with a pattern that was successfully studied
+ with the PCRE_STUDY_JIT_COMPILE option, the way that the matching is executed
+ is entirely different. However, there is still the possibility of runaway
+ matching that goes on for a very long time, and so the \fImatch_limit\fP value
+ is also used in this case (but in a different way) to limit how long the
+ matching can continue.
+ .P
+ The default value for the limit can be set when PCRE is built; the default
  default is 10 million, which handles all but the most extreme cases. You can
- reduce the default by suppling \fBpcre_exec()\fR with a \fRpcre_extra\fR block
+ override the default by suppling \fBpcre_exec()\fP with a \fBpcre_extra\fP
- in which \fImatch_limit\fR is set to a smaller value, and
+ block in which \fImatch_limit\fP is set, and PCRE_EXTRA_MATCH_LIMIT is set in
- PCRE_EXTRA_MATCH_LIMIT is set in the \fIflags\fR field. If the limit is
+ the \fIflags\fP field. If the limit is exceeded, \fBpcre_exec()\fP returns
- exceeded, \fBpcre_exec()\fR returns PCRE_ERROR_MATCHLIMIT.
+ PCRE_ERROR_MATCHLIMIT.
+ .P
- The \fIpcre_callout\fR field is used in conjunction with the "callout" feature,
+ The \fImatch_limit_recursion\fP field is similar to \fImatch_limit\fP, but
- which is described in the \fBpcrecallout\fR documentation.
+ instead of limiting the total number of times that \fBmatch()\fP is called, it
+ limits the depth of recursion. The recursion depth is a smaller number than the
- The PCRE_ANCHORED option can be passed in the \fIoptions\fR argument, whose
+ total number of calls, because not all calls to \fBmatch()\fP are recursive.
- unused bits must be zero. This limits \fBpcre_exec()\fR to matching at the
+ This limit is of use only if it is set smaller than \fImatch_limit\fP.
- first matching position. However, if a pattern was compiled with PCRE_ANCHORED,
+ .P
- or turned out to be anchored by virtue of its contents, it cannot be made
+ Limiting the recursion depth limits the amount of machine stack that can be
- unachored at matching time.
+ used, or, when PCRE has been compiled to use memory on the heap instead of the
+ stack, the amount of heap memory that can be used. This limit is relevant, and
- There are also three further options that can be set only at matching time:
+ is ignored, when the pattern was successfully studied with
+ PCRE_STUDY_JIT_COMPILE.
+ .P
+ The default value for \fImatch_limit_recursion\fP can be set when PCRE is
+ built; the default default is the same value as the default for
+ \fImatch_limit\fP. You can override the default by suppling \fBpcre_exec()\fP
+ with a \fBpcre_extra\fP block in which \fImatch_limit_recursion\fP is set, and
+ PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the \fIflags\fP field. If the limit
+ is exceeded, \fBpcre_exec()\fP returns PCRE_ERROR_RECURSIONLIMIT.
+ .P
+ The \fIcallout_data\fP field is used in conjunction with the "callout" feature,
+ and is described in the
+ .\" HREF
+ \fBpcrecallout\fP
+ .\"
+ documentation.
+ .P
+ The \fItables\fP field is used to pass a character tables pointer to
+ \fBpcre_exec()\fP; this overrides the value that is stored with the compiled
+ pattern. A non-NULL value is stored with the compiled pattern only if custom
+ tables were supplied to \fBpcre_compile()\fP via its \fItableptr\fP argument.
+ If NULL is passed to \fBpcre_exec()\fP using this mechanism, it forces PCRE's
+ internal tables to be used. This facility is helpful when re-using patterns
+ that have been saved after compiling with an external set of tables, because
+ the external tables might be at a different address when \fBpcre_exec()\fP is
+ called. See the
+ .\" HREF
+ \fBpcreprecompile\fP
+ .\"
+ documentation for a discussion of saving compiled patterns for later use.
+ .P
+ If PCRE_EXTRA_MARK is set in the \fIflags\fP field, the \fImark\fP field must
+ be set to point to a \fBchar *\fP variable. If the pattern contains any
+ backtracking control verbs such as (*MARK:NAME), and the execution ends up with
+ a name to pass back, a pointer to the name string (zero terminated) is placed
+ in the variable pointed to by the \fImark\fP field. The names are within the
+ compiled pattern; if you wish to retain such a name you must copy it before
+ freeing the memory of a compiled pattern. If there is no name to pass back, the
+ variable pointed to by the \fImark\fP field set to NULL. For details of the
+ backtracking control verbs, see the section entitled
+ .\" HTML <a href="pcrepattern#backtrackcontrol">
+ .\" </a>
+ "Backtracking control"
+ .\"
+ in the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ documentation.
+ .
+ .
+ .\" HTML <a name="execoptions"></a>
+ .SS "Option bits for \fBpcre_exec()\fP"
+ .rs
+ .sp
+ The unused bits of the \fIoptions\fP argument for \fBpcre_exec()\fP must be
+ zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
+ PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
+ PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and
+ PCRE_PARTIAL_HARD.
+ .sp
+   PCRE_ANCHORED
+ .sp
+ The PCRE_ANCHORED option limits \fBpcre_exec()\fP to matching at the first
+ matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out
+ to be anchored by virtue of its contents, it cannot be made unachored at
+ matching time.
+ .sp
+   PCRE_BSR_ANYCRLF
+   PCRE_BSR_UNICODE
+ .sp
+ These options (which are mutually exclusive) control what the \eR escape
+ sequence matches. The choice is either to match only CR, LF, or CRLF, or to
+ match any Unicode newline sequence. These options override the choice that was
+ made or defaulted when the pattern was compiled.
+ .sp
+   PCRE_NEWLINE_CR
+   PCRE_NEWLINE_LF
+   PCRE_NEWLINE_CRLF
+   PCRE_NEWLINE_ANYCRLF
+   PCRE_NEWLINE_ANY
+ .sp
+ These options override the newline definition that was chosen or defaulted when
+ the pattern was compiled. For details, see the description of
+ \fBpcre_compile()\fP above. During matching, the newline choice affects the
+ behaviour of the dot, circumflex, and dollar metacharacters. It may also alter
+ the way the match position is advanced after a match failure for an unanchored
+ pattern.
+ .P
+ When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a
+ match attempt for an unanchored pattern fails when the current position is at a
+ CRLF sequence, and the pattern contains no explicit matches for CR or LF
+ characters, the match position is advanced by two characters instead of one, in
+ other words, to after the CRLF.
+ .P
+ The above rule is a compromise that makes the most common cases work as
+ expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not
+ set), it does not match the string "\er\enA" because, after failing at the
+ start, it skips both the CR and the LF before retrying. However, the pattern
+ [\er\en]A does match that string, because it contains an explicit CR or LF
+ reference, and so advances only by one character after the first failure.
+ .P
+ An explicit match for CR of LF is either a literal appearance of one of those
+ characters, or one of the \er or \en escape sequences. Implicit matches such as
+ [^X] do not count, nor does \es (which includes CR and LF in the characters
+ that it matches).
+ .P
+ Notwithstanding the above, anomalous effects may still occur when CRLF is a
+ valid newline sequence and explicit \er or \en escapes appear in the pattern.
+ .sp
    PCRE_NOTBOL
+ .sp
- The first character of the string is not the beginning of a line, so the
+ This option specifies that first character of the subject string is not the
- circumflex metacharacter should not match before it. Setting this without
+ beginning of a line, so the circumflex metacharacter should not match before
- PCRE_MULTILINE (at compile time) causes circumflex never to match.
+ it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex
+ never to match. This option affects only the behaviour of the circumflex
+ metacharacter. It does not affect \eA.
+ .sp
    PCRE_NOTEOL
+ .sp
- The end of the string is not the end of a line, so the dollar metacharacter
+ This option specifies that the end of the subject string is not the end of a
- should not match it nor (except in multiline mode) a newline immediately before
+ line, so the dollar metacharacter should not match it nor (except in multiline
- it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never
+ mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at
- to match.
+ compile time) causes dollar never to match. This option affects only the
+ behaviour of the dollar metacharacter. It does not affect \eZ or \ez.
+ .sp
    PCRE_NOTEMPTY
+ .sp
  An empty string is not considered to be a valid match if this option is set. If
  there are alternatives in the pattern, they are tried. If all the alternatives
  match the empty string, the entire match fails. For example, if the pattern
+ .sp
    a?b?
+ .sp
- is applied to a string not beginning with "a" or "b", it matches the empty
+ is applied to a string not beginning with "a" or "b", it matches an empty
  string at the start of the subject. With PCRE_NOTEMPTY set, this match is not
  valid, so PCRE searches further into the string for occurrences of "a" or "b".
+ .sp
- Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case
+   PCRE_NOTEMPTY_ATSTART
- of a pattern match of the empty string within its \fBsplit()\fR function, and
+ .sp
- when using the /g modifier. It is possible to emulate Perl's behaviour after
+ This is like PCRE_NOTEMPTY, except that an empty string match that is not at
- matching a null string by first trying the match again at the same offset with
+ the start of the subject is permitted. If the pattern is anchored, such a match
- PCRE_NOTEMPTY set, and then if that fails by advancing the starting offset (see
+ can occur only if the pattern contains \eK.
- below) and trying an ordinary match again.
+ .P
+ Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it
- The subject string is passed to \fBpcre_exec()\fR as a pointer in
+ does make a special case of a pattern match of the empty string within its
- \fIsubject\fR, a length in \fIlength\fR, and a starting offset in
+ \fBsplit()\fP function, and when using the /g modifier. It is possible to
- \fIstartoffset\fR. Unlike the pattern string, the subject may contain binary
+ emulate Perl's behaviour after matching a null string by first trying the match
- zero bytes. When the starting offset is zero, the search for a match starts at
+ again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then
- the beginning of the subject, and this is by far the most common case.
+ if that fails, by advancing the starting offset (see below) and trying an
+ ordinary match again. There is some code that demonstrates how to do this in
- If the pattern was compiled with the PCRE_UTF8 option, the subject must be a
+ the
- sequence of bytes that is a valid UTF-8 string. If an invalid UTF-8 string is
+ .\" HREF
- passed, PCRE's behaviour is not defined.
+ \fBpcredemo\fP
+ .\"
+ sample program. In the most general case, you have to check to see if the
+ newline convention recognizes CRLF as a newline, and if so, and the current
+ character is CR followed by LF, advance the starting offset by two characters
+ instead of one.
+ .sp
+   PCRE_NO_START_OPTIMIZE
+ .sp
+ There are a number of optimizations that \fBpcre_exec()\fP uses at the start of
+ a match, in order to speed up the process. For example, if it is known that an
+ unanchored match must start with a specific character, it searches the subject
+ for that character, and fails immediately if it cannot find it, without
+ actually running the main matching function. This means that a special item
+ such as (*COMMIT) at the start of a pattern is not considered until after a
+ suitable starting point for the match has been found. When callouts or (*MARK)
+ items are in use, these "start-up" optimizations can cause them to be skipped
+ if the pattern is never actually used. The start-up optimizations are in effect
+ a pre-scan of the subject that takes place before the pattern is run.
+ .P
+ The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly
+ causing performance to suffer, but ensuring that in cases where the result is
+ "no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK)
+ are considered at every possible starting position in the subject string. If
+ PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching
+ time.
+ .P
+ Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation.
+ Consider the pattern
+ .sp
+   (*COMMIT)ABC
+ .sp
+ When this is compiled, PCRE records the fact that a match must start with the
+ character "A". Suppose the subject string is "DEFABC". The start-up
+ optimization scans along the subject, finds "A" and runs the first match
+ attempt from there. The (*COMMIT) item means that the pattern must match the
+ current starting position, which in this case, it does. However, if the same
+ match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the
+ subject string does not happen. The first match attempt is run starting from
+ "D" and when this fails, (*COMMIT) prevents any further matches being tried, so
+ the overall result is "no match". If the pattern is studied, more start-up
+ optimizations may be used. For example, a minimum length for the subject may be
+ recorded. Consider the pattern
+ .sp
+   (*MARK:A)(X|Y)
+ .sp
+ The minimum length for a match is one character. If the subject is "ABC", there
+ will be attempts to match "ABC", "BC", "C", and then finally an empty string.
+ If the pattern is studied, the final attempt does not take place, because PCRE
+ knows that the subject is too short, and so the (*MARK) is never encountered.
+ In this case, studying the pattern does not affect the overall match result,
+ which is still "no match", but it does affect the auxiliary information that is
+ returned.
+ .sp
+   PCRE_NO_UTF8_CHECK
+ .sp
+ When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8
+ string is automatically checked when \fBpcre_exec()\fP is subsequently called.
+ The value of \fIstartoffset\fP is also checked to ensure that it points to the
+ start of a UTF-8 character. There is a discussion about the validity of UTF-8
+ strings in the
+ .\" HTML <a href="pcre.html#utf8strings">
+ .\" </a>
+ section on UTF-8 support
+ .\"
+ in the main
+ .\" HREF
+ \fBpcre\fP
+ .\"
+ page. If an invalid UTF-8 sequence of bytes is found, \fBpcre_exec()\fP returns
+ the error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is
+ a truncated UTF-8 character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
+ both cases, information about the precise nature of the error may also be
+ returned (see the descriptions of these errors in the section entitled \fIError
+ return values from\fP \fBpcre_exec()\fP
+ .\" HTML <a href="#errorlist">
+ .\" </a>
+ below).
+ .\"
+ If \fIstartoffset\fP contains a value that does not point to the start of a
+ UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is
+ returned.
+ .P
+ If you already know that your subject is valid, and you want to skip these
+ checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when
+ calling \fBpcre_exec()\fP. You might want to do this for the second and
+ subsequent calls to \fBpcre_exec()\fP if you are making repeated calls to find
+ all the matches in a single subject string. However, you should be sure that
+ the value of \fIstartoffset\fP points to the start of a UTF-8 character (or the
+ end of the subject). When PCRE_NO_UTF8_CHECK is set, the effect of passing an
+ invalid UTF-8 string as a subject or an invalid value of \fIstartoffset\fP is
+ undefined. Your program may crash.
+ .sp
+   PCRE_PARTIAL_HARD
+   PCRE_PARTIAL_SOFT
+ .sp
+ These options turn on the partial matching feature. For backwards
+ compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match
+ occurs if the end of the subject string is reached successfully, but there are
+ not enough subject characters to complete the match. If this happens when
+ PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by
+ testing any remaining alternatives. Only if no complete match can be found is
+ PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words,
+ PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match,
+ but only if no complete match can be found.
+ .P
+ If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a
+ partial match is found, \fBpcre_exec()\fP immediately returns
+ PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words,
+ when PCRE_PARTIAL_HARD is set, a partial match is considered to be more
+ important that an alternative complete match.
+ .P
+ In both cases, the portion of the string that was inspected when the partial
+ match was found is set as the first matching string. There is a more detailed
+ discussion of partial and multi-segment matching, with examples, in the
+ .\" HREF
+ \fBpcrepartial\fP
+ .\"
+ documentation.
+ .
+ .
+ .SS "The string to be matched by \fBpcre_exec()\fP"
+ .rs
+ .sp
+ The subject string is passed to \fBpcre_exec()\fP as a pointer in
+ \fIsubject\fP, a length (in bytes) in \fIlength\fP, and a starting byte offset
+ in \fIstartoffset\fP. If this is negative or greater than the length of the
+ subject, \fBpcre_exec()\fP returns PCRE_ERROR_BADOFFSET. When the starting
+ offset is zero, the search for a match starts at the beginning of the subject,
+ and this is by far the most common case. In UTF-8 mode, the byte offset must
+ point to the start of a UTF-8 character (or the end of the subject). Unlike the
+ pattern string, the subject may contain binary zero bytes.
+ .P
  A non-zero starting offset is useful when searching for another match in the
- same subject by calling \fBpcre_exec()\fR again after a previous success.
+ same subject by calling \fBpcre_exec()\fP again after a previous success.
- Setting \fIstartoffset\fR differs from just passing over a shortened string and
+ Setting \fIstartoffset\fP differs from just passing over a shortened string and
  setting PCRE_NOTBOL in the case of a pattern that begins with any kind of
  lookbehind. For example, consider the pattern
+ .sp
-   \\Biss\\B
+   \eBiss\eB
+ .sp
- which finds occurrences of "iss" in the middle of words. (\\B matches only if
+ which finds occurrences of "iss" in the middle of words. (\eB matches only if
  the current position in the subject is not a word boundary.) When applied to
- the string "Mississipi" the first call to \fBpcre_exec()\fR finds the first
+ the string "Mississipi" the first call to \fBpcre_exec()\fP finds the first
- occurrence. If \fBpcre_exec()\fR is called again with just the remainder of the
+ occurrence. If \fBpcre_exec()\fP is called again with just the remainder of the
- subject, namely "issipi", it does not match, because \\B is always false at the
+ subject, namely "issipi", it does not match, because \eB is always false at the
  start of the subject, which is deemed to be a word boundary. However, if
- \fBpcre_exec()\fR is passed the entire string again, but with \fIstartoffset\fR
+ \fBpcre_exec()\fP is passed the entire string again, but with \fIstartoffset\fP
  set to 4, it finds the second occurrence of "iss" because it is able to look
  behind the starting point to discover that it is preceded by a letter.
+ .P
+ Finding all the matches in a subject is tricky when the pattern can match an
+ empty string. It is possible to emulate Perl's /g behaviour by first trying the
+ match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and
+ PCRE_ANCHORED options, and then if that fails, advancing the starting offset
+ and trying an ordinary match again. There is some code that demonstrates how to
+ do this in the
+ .\" HREF
+ \fBpcredemo\fP
+ .\"
+ sample program. In the most general case, you have to check to see if the
+ newline convention recognizes CRLF as a newline, and if so, and the current
+ character is CR followed by LF, advance the starting offset by two characters
+ instead of one.
+ .P
  If a non-zero starting offset is passed when the pattern is anchored, one
- attempt to match at the given offset is tried. This can only succeed if the
+ attempt to match at the given offset is made. This can only succeed if the
  pattern does not require the match to be at the start of the subject.
+ .
+ .
+ .SS "How \fBpcre_exec()\fP returns captured substrings"
+ .rs
+ .sp
  In general, a pattern matches a certain portion of the subject, and in
  addition, further substrings from the subject may be picked out by parts of the
  pattern. Following the usage in Jeffrey Friedl's book, this is called
  "capturing" in what follows, and the phrase "capturing subpattern" is used for
  a fragment of a pattern that picks out a substring. PCRE supports several other
  kinds of parenthesized subpattern that do not cause substrings to be captured.
+ .P
- Captured substrings are returned to the caller via a vector of integer offsets
+ Captured substrings are returned to the caller via a vector of integers whose
- whose address is passed in \fIovector\fR. The number of elements in the vector
+ address is passed in \fIovector\fP. The number of elements in the vector is
- is passed in \fIovecsize\fR. The first two-thirds of the vector is used to pass
+ passed in \fIovecsize\fP, which must be a non-negative number. \fBNote\fP: this
- back captured substrings, each substring using a pair of integers. The
+ argument is NOT the size of \fIovector\fP in bytes.
- remaining third of the vector is used as workspace by \fBpcre_exec()\fR while
+ .P
- matching capturing subpatterns, and is not available for passing back
+ The first two-thirds of the vector is used to pass back captured substrings,
- information. The length passed in \fIovecsize\fR should always be a multiple of
+ each substring using a pair of integers. The remaining third of the vector is
- three. If it is not, it is rounded down.
+ used as workspace by \fBpcre_exec()\fP while matching capturing subpatterns,
+ and is not available for passing back information. The number passed in
- When a match has been successful, information about captured substrings is
+ \fIovecsize\fP should always be a multiple of three. If it is not, it is
- returned in pairs of integers, starting at the beginning of \fIovector\fR, and
+ rounded down.
- continuing up to two-thirds of its length at the most. The first element of a
+ .P
- pair is set to the offset of the first character in a substring, and the second
+ When a match is successful, information about captured substrings is returned
- is set to the offset of the first character after the end of a substring. The
+ in pairs of integers, starting at the beginning of \fIovector\fP, and
- first pair, \fIovector[0]\fR and \fIovector[1]\fR, identify the portion of the
+ continuing up to two-thirds of its length at the most. The first element of
- subject string matched by the entire pattern. The next pair is used for the
+ each pair is set to the byte offset of the first character in a substring, and
- first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fR
+ the second is set to the byte offset of the first character after the end of a
- is the number of pairs that have been set. If there are no capturing
+ substring. \fBNote\fP: these values are always byte offsets, even in UTF-8
- subpatterns, the return value from a successful match is 1, indicating that
+ mode. They are not character counts.
- just the first pair of offsets has been set.
+ .P
+ The first pair of integers, \fIovector[0]\fP and \fIovector[1]\fP, identify the
- Some convenience functions are provided for extracting the captured substrings
+ portion of the subject string matched by the entire pattern. The next pair is
- as separate strings. These are described in the following section.
+ used for the first capturing subpattern, and so on. The value returned by
+ \fBpcre_exec()\fP is one more than the highest numbered pair that has been set.
- It is possible for an capturing subpattern number \fIn+1\fR to match some
+ For example, if two substrings have been captured, the returned value is 3. If
- part of the subject when subpattern \fIn\fR has not been used at all. For
+ there are no capturing subpatterns, the return value from a successful match is
- example, if the string "abc" is matched against the pattern (a|(z))(bc)
+, indicating that just the first pair of offsets has been set.
- subpatterns 1 and 3 are matched, but 2 is not. When this happens, both offset
+ .P
- values corresponding to the unused subpattern are set to -1.
  If a capturing subpattern is matched repeatedly, it is the last portion of the
- string that it matched that gets returned.
+ string that it matched that is returned.
+ .P
- If the vector is too small to hold all the captured substrings, it is used as
+ If the vector is too small to hold all the captured substring offsets, it is
- far as possible (up to two-thirds of its length), and the function returns a
+ used as far as possible (up to two-thirds of its length), and the function
- value of zero. In particular, if the substring offsets are not of interest,
+ returns a value of zero. If the substring offsets are not of interest,
- \fBpcre_exec()\fR may be called with \fIovector\fR passed as NULL and
+ \fBpcre_exec()\fP may be called with \fIovector\fP passed as NULL and
- \fIovecsize\fR as zero. However, if the pattern contains back references and
+ \fIovecsize\fP as zero. However, if the pattern contains back references and
- the \fIovector\fR isn't big enough to remember the related substrings, PCRE has
+ the \fIovector\fP is not big enough to remember the related substrings, PCRE
- to get additional memory for use during matching. Thus it is usually advisable
+ has to get additional memory for use during matching. Thus it is usually
- to supply an \fIovector\fR.
+ advisable to supply an \fIovector\fP.
+ .P
- Note that \fBpcre_info()\fR can be used to find out how many capturing
+ The \fBpcre_fullinfo()\fP function can be used to find out how many capturing
  subpatterns there are in a compiled pattern. The smallest size for
- \fIovector\fR that will allow for \fIn\fR captured substrings, in addition to
+ \fIovector\fP that will allow for \fIn\fP captured substrings, in addition to
- the offsets of the substring matched by the whole pattern, is (\fIn\fR+1)*3.
+ the offsets of the substring matched by the whole pattern, is (\fIn\fP+1)*3.
+ .P
- If \fBpcre_exec()\fR fails, it returns a negative number. The following are
+ It is possible for capturing subpattern number \fIn+1\fP to match some part of
+ the subject when subpattern \fIn\fP has not been used at all. For example, if
+ the string "abc" is matched against the pattern (a|(z))(bc) the return from the
+ function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this
+ happens, both values in the offset pairs corresponding to unused subpatterns
+ are set to -1.
+ .P
+ Offset values that correspond to unused subpatterns at the end of the
+ expression are also set to -1. For example, if the string "abc" is matched
+ against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The
+ return from the function is 2, because the highest used capturing subpattern
+ number is 1, and the offsets for for the second and third capturing subpatterns
+ (assuming the vector is large enough, of course) are set to -1.
+ .P
+ \fBNote\fP: Elements of \fIovector\fP that do not correspond to capturing
+ parentheses in the pattern are never changed. That is, if a pattern contains
+ \fIn\fP capturing parentheses, no more than \fIovector[0]\fP to
+ \fIovector[2n+1]\fP are set by \fBpcre_exec()\fP. The other elements retain
+ whatever values they previously had.
+ .P
+ Some convenience functions are provided for extracting the captured substrings
+ as separate strings. These are described below.
+ .
+ .
+ .\" HTML <a name="errorlist"></a>
+ .SS "Error return values from \fBpcre_exec()\fP"
+ .rs
+ .sp
+ If \fBpcre_exec()\fP fails, it returns a negative number. The following are
  defined in the header file:
+ .sp
    PCRE_ERROR_NOMATCH        (-1)
+ .sp
  The subject string did not match the pattern.
+ .sp
    PCRE_ERROR_NULL           (-2)
+ .sp
- Either \fIcode\fR or \fIsubject\fR was passed as NULL, or \fIovector\fR was
+ Either \fIcode\fP or \fIsubject\fP was passed as NULL, or \fIovector\fP was
- NULL and \fIovecsize\fR was not zero.
+ NULL and \fIovecsize\fP was not zero.
+ .sp
    PCRE_ERROR_BADOPTION      (-3)
+ .sp
- An unrecognized bit was set in the \fIoptions\fR argument.
+ An unrecognized bit was set in the \fIoptions\fP argument.
+ .sp
    PCRE_ERROR_BADMAGIC       (-4)
+ .sp
  PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch
- the case when it is passed a junk pointer. This is the error it gives when the
+ the case when it is passed a junk pointer and to detect when a pattern that was
- magic number isn't present.
+ compiled in an environment of one endianness is run in an environment with the
+ other endianness. This is the error that PCRE gives when the magic number is
-   PCRE_ERROR_UNKNOWN_NODE   (-5)
+ not present.
+ .sp
+   PCRE_ERROR_UNKNOWN_OPCODE (-5)
+ .sp
  While running the pattern match, an unknown item was encountered in the
  compiled pattern. This error could be caused by a bug in PCRE or by overwriting
  of the compiled pattern.
+ .sp
    PCRE_ERROR_NOMEMORY       (-6)
+ .sp
- If a pattern contains back references, but the \fIovector\fR that is passed to
+ If a pattern contains back references, but the \fIovector\fP that is passed to
- \fBpcre_exec()\fR is not big enough to remember the referenced substrings, PCRE
+ \fBpcre_exec()\fP is not big enough to remember the referenced substrings, PCRE
  gets a block of memory at the start of matching to use for this purpose. If the
- call via \fBpcre_malloc()\fR fails, this error is given. The memory is freed at
+ call via \fBpcre_malloc()\fP fails, this error is given. The memory is
- the end of matching.
+ automatically freed at the end of matching.
+ .P
+ This error is also given if \fBpcre_stack_malloc()\fP fails in
+ \fBpcre_exec()\fP. This can happen only when PCRE has been compiled with
+ \fB--disable-stack-for-recursion\fP.
+ .sp
    PCRE_ERROR_NOSUBSTRING    (-7)
+ .sp
- This error is used by the \fBpcre_copy_substring()\fR,
+ This error is used by the \fBpcre_copy_substring()\fP,
- \fBpcre_get_substring()\fR, and \fBpcre_get_substring_list()\fR functions (see
+ \fBpcre_get_substring()\fP, and \fBpcre_get_substring_list()\fP functions (see
- below). It is never returned by \fBpcre_exec()\fR.
+ below). It is never returned by \fBpcre_exec()\fP.
+ .sp
    PCRE_ERROR_MATCHLIMIT     (-8)
+ .sp
- The recursion and backtracking limit, as specified by the \fImatch_limit\fR
+ The backtracking limit, as specified by the \fImatch_limit\fP field in a
- field in a \fBpcre_extra\fR structure (or defaulted) was reached. See the
+ \fBpcre_extra\fP structure (or defaulted) was reached. See the description
- description above.
+ above.
+ .sp
    PCRE_ERROR_CALLOUT        (-9)
+ .sp
- This error is never generated by \fBpcre_exec()\fR itself. It is provided for
+ This error is never generated by \fBpcre_exec()\fP itself. It is provided for
  use by callout functions that want to yield a distinctive error code. See the
- \fBpcrecallout\fR documentation for details.
+ .\" HREF
+ \fBpcrecallout\fP
- .SH EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
+ .\"
+ documentation for details.
+ .sp
+   PCRE_ERROR_BADUTF8        (-10)
+ .sp
+ A string that contains an invalid UTF-8 byte sequence was passed as a subject,
+ and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector
+ (\fIovecsize\fP) is at least 2, the byte offset to the start of the the invalid
+ UTF-8 character is placed in the first element, and a reason code is placed in
+ the second element. The reason codes are listed in the
+ .\" HTML <a href="#badutf8reasons">
+ .\" </a>
+ following section.
+ .\"
+ For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a
+ truncated UTF-8 character at the end of the subject (reason codes 1 to 5),
+ PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
+ .sp
+   PCRE_ERROR_BADUTF8_OFFSET (-11)
+ .sp
+ The UTF-8 byte sequence that was passed as a subject was checked and found to
+ be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of
+ \fIstartoffset\fP did not point to the beginning of a UTF-8 character or the
+ end of the subject.
+ .sp
+   PCRE_ERROR_PARTIAL        (-12)
+ .sp
+ The subject string did not match, but it did match partially. See the
+ .\" HREF
+ \fBpcrepartial\fP
+ .\"
+ documentation for details of partial matching.
+ .sp
+   PCRE_ERROR_BADPARTIAL     (-13)
+ .sp
+ This code is no longer in use. It was formerly returned when the PCRE_PARTIAL
+ option was used with a compiled pattern containing items that were not
+ supported for partial matching. From release 8.00 onwards, there are no
+ restrictions on partial matching.
+ .sp
+   PCRE_ERROR_INTERNAL       (-14)
+ .sp
+ An unexpected internal error has occurred. This error could be caused by a bug
+ in PCRE or by overwriting of the compiled pattern.
+ .sp
+   PCRE_ERROR_BADCOUNT       (-15)
+ .sp
+ This error is given if the value of the \fIovecsize\fP argument is negative.
+ .sp
+   PCRE_ERROR_RECURSIONLIMIT (-21)
+ .sp
+ The internal recursion limit, as specified by the \fImatch_limit_recursion\fP
+ field in a \fBpcre_extra\fP structure (or defaulted) was reached. See the
+ description above.
+ .sp
+   PCRE_ERROR_BADNEWLINE     (-23)
+ .sp
+ An invalid combination of PCRE_NEWLINE_\fIxxx\fP options was given.
+ .sp
+   PCRE_ERROR_BADOFFSET      (-24)
+ .sp
+ The value of \fIstartoffset\fP was negative or greater than the length of the
+ subject, that is, the value in \fIlength\fP.
+ .sp
+   PCRE_ERROR_SHORTUTF8      (-25)
+ .sp
+ This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string
+ ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set.
+ Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in
+ fact sufficient to detect this case, but this special error code for
+ PCRE_PARTIAL_HARD precedes the implementation of returned information; it is
+ retained for backwards compatibility.
+ .sp
+   PCRE_ERROR_RECURSELOOP    (-26)
+ .sp
+ This error is returned when \fBpcre_exec()\fP detects a recursion loop within
+ the pattern. Specifically, it means that either the whole pattern or a
+ subpattern has been called recursively for the second time at the same position
+ in the subject string. Some simple patterns that might do this are detected and
+ faulted at compile time, but more complicated cases, in particular mutual
+ recursions between two different subpatterns, cannot be detected until run
+ time.
+ .sp
+   PCRE_ERROR_JIT_STACKLIMIT (-27)
+ .sp
+ This error is returned when a pattern that was successfully studied using the
+ PCRE_STUDY_JIT_COMPILE option is matched, but the memory available for the
+ just-in-time processing stack is not large enough. See the
+ .\" HREF
+ \fBpcrejit\fP
+ .\"
+ documentation for more details.
+ .P
+ Error numbers -16 to -20 and -22 are not used by \fBpcre_exec()\fP.
+ .
+ .
+ .\" HTML <a name="badutf8reasons"></a>
+ .SS "Reason codes for invalid UTF-8 strings"
  .rs
  .sp
- .B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR,
+ When \fBpcre_exec()\fP returns either PCRE_ERROR_BADUTF8 or
+ PCRE_ERROR_SHORTUTF8, and the size of the output vector (\fIovecsize\fP) is at
+ least 2, the offset of the start of the invalid UTF-8 character is placed in
+ the first output vector element (\fIovector[0]\fP) and a reason code is placed
+ in the second element (\fIovector[1]\fP). The reason codes are given names in
+ the \fBpcre.h\fP header file:
+ .sp
+   PCRE_UTF8_ERR1
+   PCRE_UTF8_ERR2
+   PCRE_UTF8_ERR3
+   PCRE_UTF8_ERR4
+   PCRE_UTF8_ERR5
+ .sp
+ The string ends with a truncated UTF-8 character; the code specifies how many
+ bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
+ no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
+ allows for up to 6 bytes, and this is checked first; hence the possibility of
+or 5 missing bytes.
+ .sp
+   PCRE_UTF8_ERR6
+   PCRE_UTF8_ERR7
+   PCRE_UTF8_ERR8
+   PCRE_UTF8_ERR9
+   PCRE_UTF8_ERR10
+ .sp
+ The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
+ character do not have the binary value 0b10 (that is, either the most
+ significant bit is 0, or the next bit is 1).
+ .sp
+   PCRE_UTF8_ERR11
+   PCRE_UTF8_ERR12
+ .sp
+ A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
+ these code points are excluded by RFC 3629.
+ .sp
+   PCRE_UTF8_ERR13
+ .sp
+ A 4-byte character has a value greater than 0x10fff; these code points are
+ excluded by RFC 3629.
+ .sp
+   PCRE_UTF8_ERR14
+ .sp
+ A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
+ code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
+ from UTF-8.
+ .sp
+   PCRE_UTF8_ERR15
+   PCRE_UTF8_ERR16
+   PCRE_UTF8_ERR17
+   PCRE_UTF8_ERR18
+   PCRE_UTF8_ERR19
+ .sp
+ A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
+ value that can be represented by fewer bytes, which is invalid. For example,
+ the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
+ one byte.
+ .sp
+   PCRE_UTF8_ERR20
+ .sp
+ The two most significant bits of the first byte of a character have the binary
+ value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
+ byte can only validly occur as the second or subsequent byte of a multi-byte
+ character.
+ .sp
+   PCRE_UTF8_ERR21
+ .sp
+ The first byte of a character has the value 0xfe or 0xff. These values can
+ never occur in a valid UTF-8 string.
+ .
+ .
+ .SH "EXTRACTING CAPTURED SUBSTRINGS BY NUMBER"
+ .rs
+ .sp
+ .B int pcre_copy_substring(const char *\fIsubject\fP, int *\fIovector\fP,
  .ti +5n
- .B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR,
+ .B int \fIstringcount\fP, int \fIstringnumber\fP, char *\fIbuffer\fP,
  .ti +5n
- .B int \fIbuffersize\fR);
+ .B int \fIbuffersize\fP);
  .PP
- .br
+ .B int pcre_get_substring(const char *\fIsubject\fP, int *\fIovector\fP,
- .B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR,
  .ti +5n
- .B int \fIstringcount\fR, int \fIstringnumber\fR,
+ .B int \fIstringcount\fP, int \fIstringnumber\fP,
  .ti +5n
- .B const char **\fIstringptr\fR);
+ .B const char **\fIstringptr\fP);
  .PP
- .br
+ .B int pcre_get_substring_list(const char *\fIsubject\fP,
- .B int pcre_get_substring_list(const char *\fIsubject\fR,
  .ti +5n
- .B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);"
+ .B int *\fIovector\fP, int \fIstringcount\fP, "const char ***\fIlistptr\fP);"
  .PP
  Captured substrings can be accessed directly by using the offsets returned by
- \fBpcre_exec()\fR in \fIovector\fR. For convenience, the functions
+ \fBpcre_exec()\fP in \fIovector\fP. For convenience, the functions
- \fBpcre_copy_substring()\fR, \fBpcre_get_substring()\fR, and
+ \fBpcre_copy_substring()\fP, \fBpcre_get_substring()\fP, and
- \fBpcre_get_substring_list()\fR are provided for extracting captured substrings
+ \fBpcre_get_substring_list()\fP are provided for extracting captured substrings
  as new, separate, zero-terminated strings. These functions identify substrings
  by number. The next section describes functions for extracting named
- substrings. A substring that contains a binary zero is correctly extracted and
+ substrings.
- has a further zero added on the end, but the result is not, of course,
+ .P
- a C string.
+ A substring that contains a binary zero is correctly extracted and has a
+ further zero added on the end, but the result is not, of course, a C string.
+ However, you can process such a string by referring to the length that is
+ returned by \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP.
+ Unfortunately, the interface to \fBpcre_get_substring_list()\fP is not adequate
+ for handling strings containing binary zeros, because the end of the final
+ string is not independently indicated.
+ .P
  The first three arguments are the same for all three of these functions:
- \fIsubject\fR is the subject string which has just been successfully matched,
+ \fIsubject\fP is the subject string that has just been successfully matched,
- \fIovector\fR is a pointer to the vector of integer offsets that was passed to
+ \fIovector\fP is a pointer to the vector of integer offsets that was passed to
- \fBpcre_exec()\fR, and \fIstringcount\fR is the number of substrings that were
+ \fBpcre_exec()\fP, and \fIstringcount\fP is the number of substrings that were
  captured by the match, including the substring that matched the entire regular
- expression. This is the value returned by \fBpcre_exec\fR if it is greater than
+ expression. This is the value returned by \fBpcre_exec()\fP if it is greater
- zero. If \fBpcre_exec()\fR returned zero, indicating that it ran out of space
+ than zero. If \fBpcre_exec()\fP returned zero, indicating that it ran out of
- in \fIovector\fR, the value passed as \fIstringcount\fR should be the size of
+ space in \fIovector\fP, the value passed as \fIstringcount\fP should be the
- the vector divided by three.
+ number of elements in the vector divided by three.
+ .P
- The functions \fBpcre_copy_substring()\fR and \fBpcre_get_substring()\fR
+ The functions \fBpcre_copy_substring()\fP and \fBpcre_get_substring()\fP
- extract a single substring, whose number is given as \fIstringnumber\fR. A
+ extract a single substring, whose number is given as \fIstringnumber\fP. A
- value of zero extracts the substring that matched the entire pattern, while
+ value of zero extracts the substring that matched the entire pattern, whereas
- higher values extract the captured substrings. For \fBpcre_copy_substring()\fR,
+ higher values extract the captured substrings. For \fBpcre_copy_substring()\fP,
- the string is placed in \fIbuffer\fR, whose length is given by
+ the string is placed in \fIbuffer\fP, whose length is given by
- \fIbuffersize\fR, while for \fBpcre_get_substring()\fR a new block of memory is
+ \fIbuffersize\fP, while for \fBpcre_get_substring()\fP a new block of memory is
- obtained via \fBpcre_malloc\fR, and its address is returned via
+ obtained via \fBpcre_malloc\fP, and its address is returned via
- \fIstringptr\fR. The yield of the function is the length of the string, not
+ \fIstringptr\fP. The yield of the function is the length of the string, not
- including the terminating zero, or one of
+ including the terminating zero, or one of these error codes:
+ .sp
    PCRE_ERROR_NOMEMORY       (-6)
+ .sp
- The buffer was too small for \fBpcre_copy_substring()\fR, or the attempt to get
+ The buffer was too small for \fBpcre_copy_substring()\fP, or the attempt to get
- memory failed for \fBpcre_get_substring()\fR.
+ memory failed for \fBpcre_get_substring()\fP.
+ .sp
    PCRE_ERROR_NOSUBSTRING    (-7)
+ .sp
- There is no substring whose number is \fIstringnumber\fR.
+ There is no substring whose number is \fIstringnumber\fP.
+ .P
- The \fBpcre_get_substring_list()\fR function extracts all available substrings
+ The \fBpcre_get_substring_list()\fP function extracts all available substrings
  and builds a list of pointers to them. All this is done in a single block of
- memory which is obtained via \fBpcre_malloc\fR. The address of the memory block
+ memory that is obtained via \fBpcre_malloc\fP. The address of the memory block
- is returned via \fIlistptr\fR, which is also the start of the list of string
+ is returned via \fIlistptr\fP, which is also the start of the list of string
  pointers. The end of the list is marked by a NULL pointer. The yield of the
- function is zero if all went well, or
+ function is zero if all went well, or the error code
+ .sp
    PCRE_ERROR_NOMEMORY       (-6)
+ .sp
  if the attempt to get the memory block failed.
+ .P
  When any of these functions encounter a substring that is unset, which can
- happen when capturing subpattern number \fIn+1\fR matches some part of the
+ happen when capturing subpattern number \fIn+1\fP matches some part of the
- subject, but subpattern \fIn\fR has not been used at all, they return an empty
+ subject, but subpattern \fIn\fP has not been used at all, they return an empty
  string. This can be distinguished from a genuine zero-length substring by
- inspecting the appropriate offset in \fIovector\fR, which is negative for unset
+ inspecting the appropriate offset in \fIovector\fP, which is negative for unset
  substrings.
+ .P
- The two convenience functions \fBpcre_free_substring()\fR and
+ The two convenience functions \fBpcre_free_substring()\fP and
- \fBpcre_free_substring_list()\fR can be used to free the memory returned by
+ \fBpcre_free_substring_list()\fP can be used to free the memory returned by
- a previous call of \fBpcre_get_substring()\fR or
+ a previous call of \fBpcre_get_substring()\fP or
- \fBpcre_get_substring_list()\fR, respectively. They do nothing more than call
+ \fBpcre_get_substring_list()\fP, respectively. They do nothing more than call
- the function pointed to by \fBpcre_free\fR, which of course could be called
+ the function pointed to by \fBpcre_free\fP, which of course could be called
  directly from a C program. However, PCRE is used in some situations where it is
- linked via a special interface to another programming language which cannot use
+ linked via a special interface to another programming language that cannot use
- \fBpcre_free\fR directly; it is for these cases that the functions are
+ \fBpcre_free\fP directly; it is for these cases that the functions are
  provided.
+ .
- .SH EXTRACTING CAPTURED SUBSTRINGS BY NAME
+ .
+ .SH "EXTRACTING CAPTURED SUBSTRINGS BY NAME"
  .rs
  .sp
- .B int pcre_copy_named_substring(const pcre *\fIcode\fR,
+ .B int pcre_get_stringnumber(const pcre *\fIcode\fP,
  .ti +5n
- .B const char *\fIsubject\fR, int *\fIovector\fR,
+ .B const char *\fIname\fP);
+ .PP
+ .B int pcre_copy_named_substring(const pcre *\fIcode\fP,
  .ti +5n
- .B int \fIstringcount\fR, const char *\fIstringname\fR,
+ .B const char *\fIsubject\fP, int *\fIovector\fP,
  .ti +5n
- .B char *\fIbuffer\fR, int \fIbuffersize\fR);
+ .B int \fIstringcount\fP, const char *\fIstringname\fP,
- .PP
- .br
- .B int pcre_get_stringnumber(const pcre *\fIcode\fR,
  .ti +5n
- .B const char *\fIname\fR);
+ .B char *\fIbuffer\fP, int \fIbuffersize\fP);
  .PP
- .br
+ .B int pcre_get_named_substring(const pcre *\fIcode\fP,
- .B int pcre_get_named_substring(const pcre *\fIcode\fR,
  .ti +5n
- .B const char *\fIsubject\fR, int *\fIovector\fR,
+ .B const char *\fIsubject\fP, int *\fIovector\fP,
  .ti +5n
- .B int \fIstringcount\fR, const char *\fIstringname\fR,
+ .B int \fIstringcount\fP, const char *\fIstringname\fP,
  .ti +5n
- .B const char **\fIstringptr\fR);
+ .B const char **\fIstringptr\fP);
  .PP
- To extract a substring by name, you first have to find associated number. This
+ To extract a substring by name, you first have to find associated number.
- can be done by calling \fBpcre_get_stringnumber()\fR. The first argument is the
+ For example, for this pattern
- compiled pattern, and the second is the name. For example, for this pattern
+ .sp
+   (a+)b(?<xxx>\ed+)...
-   ab(?<xxx>\\d+)...
+ .sp
+ the number of the subpattern called "xxx" is 2. If the name is known to be
- the number of the subpattern called "xxx" is 1. Given the number, you can then
+ unique (PCRE_DUPNAMES was not set), you can find the number from the name by
- extract the substring directly, or use one of the functions described in the
+ calling \fBpcre_get_stringnumber()\fP. The first argument is the compiled
- previous section. For convenience, there are also two functions that do the
+ pattern, and the second is the name. The yield of the function is the
- whole job.
+ subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of
+ that name.
- Most of the arguments of \fIpcre_copy_named_substring()\fR and
+ .P
- \fIpcre_get_named_substring()\fR are the same as those for the functions that
+ Given the number, you can extract the substring directly, or use one of the
- extract by number, and so are not re-described here. There are just two
+ functions described in the previous section. For convenience, there are also
- differences.
+ two functions that do the whole job.
+ .P
+ Most of the arguments of \fBpcre_copy_named_substring()\fP and
+ \fBpcre_get_named_substring()\fP are the same as those for the similarly named
+ functions that extract by number. As these are described in the previous
+ section, they are not re-described here. There are just two differences:
+ .P
  First, instead of a substring number, a substring name is given. Second, there
  is an extra argument, given at the start, which is a pointer to the compiled
  pattern. This is needed in order to gain access to the name-to-number
  translation table.
+ .P
- These functions call \fBpcre_get_stringnumber()\fR, and if it succeeds, they
+ These functions call \fBpcre_get_stringnumber()\fP, and if it succeeds, they
- then call \fIpcre_copy_substring()\fR or \fIpcre_get_substring()\fR, as
+ then call \fBpcre_copy_substring()\fP or \fBpcre_get_substring()\fP, as
- appropriate.
+ appropriate. \fBNOTE:\fP If PCRE_DUPNAMES is set and there are duplicate names,
+ the behaviour may not be what you want (see the next section).
- .in 0
+ .P
- Last updated: 03 February 2003
+ \fBWarning:\fP If the pattern uses the (?| feature to set up multiple
- .br
+ subpatterns with the same number, as described in the
- Copyright (c) 1997-2003 University of Cambridge.
+ .\" HTML <a href="pcrepattern.html#dupsubpatternnumber">
+ .\" </a>
+ section on duplicate subpattern numbers
+ .\"
+ in the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ page, you cannot use names to distinguish the different subpatterns, because
+ names are not included in the compiled code. The matching process uses only
+ numbers. For this reason, the use of different names for subpatterns of the
+ same number causes an error at compile time.
+ .
+ .SH "DUPLICATE SUBPATTERN NAMES"
+ .rs
+ .sp
+ .B int pcre_get_stringtable_entries(const pcre *\fIcode\fP,
+ .ti +5n
+ .B const char *\fIname\fP, char **\fIfirst\fP, char **\fIlast\fP);
+ .PP
+ When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns
+ are not required to be unique. (Duplicate names are always allowed for
+ subpatterns with the same number, created by using the (?| feature. Indeed, if
+ such subpatterns are named, they are required to use the same names.)
+ .P
+ Normally, patterns with duplicate names are such that in any one match, only
+ one of the named subpatterns participates. An example is shown in the
+ .\" HREF
+ \fBpcrepattern\fP
+ .\"
+ documentation.
+ .P
+ When duplicates are present, \fBpcre_copy_named_substring()\fP and
+ \fBpcre_get_named_substring()\fP return the first substring corresponding to
+ the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is
+ returned; no data is returned. The \fBpcre_get_stringnumber()\fP function
+ returns one of the numbers that are associated with the name, but it is not
+ defined which it is.
+ .P
+ If you want to get full details of all captured substrings for a given name,
+ you must use the \fBpcre_get_stringtable_entries()\fP function. The first
+ argument is the compiled pattern, and the second is the name. The third and
+ fourth are pointers to variables which are updated by the function. After it
+ has run, they point to the first and last entries in the name-to-number table
+ for the given name. The function itself returns the length of each entry, or
+ PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is
+ described above in the section entitled \fIInformation about a pattern\fP
+ .\" HTML <a href="#infoaboutpattern">
+ .\" </a>
+ above.
+ .\"
+ Given all the relevant entries for the name, you can extract each of their
+ numbers, and hence the captured data, if any.
+ .
+ .
+ .SH "FINDING ALL POSSIBLE MATCHES"
+ .rs
+ .sp
+ The traditional matching function uses a similar algorithm to Perl, which stops
+ when it finds the first match, starting at a given point in the subject. If you
+ want to find all possible matches, or the longest possible match, consider
+ using the alternative matching function (see below) instead. If you cannot use
+ the alternative function, but still need to find all possible matches, you
+ can kludge it up by making use of the callout facility, which is described in
+ the
+ .\" HREF
+ \fBpcrecallout\fP
+ .\"
+ documentation.
+ .P
+ What you have to do is to insert a callout right at the end of the pattern.
+ When your callout function is called, extract and save the current matched
+ substring. Then return 1, which forces \fBpcre_exec()\fP to backtrack and try
+ other alternatives. Ultimately, when it runs out of matches, \fBpcre_exec()\fP
+ will yield PCRE_ERROR_NOMATCH.
+ .
+ .
+ .\" HTML <a name="dfamatch"></a>
+ .SH "MATCHING A PATTERN: THE ALTERNATIVE FUNCTION"
+ .rs
+ .sp
+ .B int pcre_dfa_exec(const pcre *\fIcode\fP, "const pcre_extra *\fIextra\fP,"
+ .ti +5n
+ .B "const char *\fIsubject\fP," int \fIlength\fP, int \fIstartoffset\fP,
+ .ti +5n
+ .B int \fIoptions\fP, int *\fIovector\fP, int \fIovecsize\fP,
+ .ti +5n
+ .B int *\fIworkspace\fP, int \fIwscount\fP);
+ .P
+ The function \fBpcre_dfa_exec()\fP is called to match a subject string against
+ a compiled pattern, using a matching algorithm that scans the subject string
+ just once, and does not backtrack. This has different characteristics to the
+ normal algorithm, and is not compatible with Perl. Some of the features of PCRE
+ patterns are not supported. Nevertheless, there are times when this kind of
+ matching can be useful. For a discussion of the two matching algorithms, and a
+ list of features that \fBpcre_dfa_exec()\fP does not support, see the
+ .\" HREF
+ \fBpcrematching\fP
+ .\"
+ documentation.
+ .P
+ The arguments for the \fBpcre_dfa_exec()\fP function are the same as for
+ \fBpcre_exec()\fP, plus two extras. The \fIovector\fP argument is used in a
+ different way, and this is described below. The other common arguments are used
+ in the same way as for \fBpcre_exec()\fP, so their description is not repeated
+ here.
+ .P
+ The two additional arguments provide workspace for the function. The workspace
+ vector should contain at least 20 elements. It is used for keeping track of
+ multiple paths through the pattern tree. More workspace will be needed for
+ patterns and subjects where there are a lot of potential matches.
+ .P
+ Here is an example of a simple call to \fBpcre_dfa_exec()\fP:
+ .sp
+   int rc;
+   int ovector[10];
+   int wspace[20];
+   rc = pcre_dfa_exec(
+     re,             /* result of pcre_compile() */
+     NULL,           /* we didn't study the pattern */
+     "some string",  /* the subject string */
+,             /* the length of the subject string */
+,              /* start at offset 0 in the subject */
+,              /* default options */
+     ovector,        /* vector of integers for substring information */
+,             /* number of elements (NOT size in bytes) */
+     wspace,         /* working space vector */
+);            /* number of elements (NOT size in bytes) */
+ .
+ .SS "Option bits for \fBpcre_dfa_exec()\fP"
+ .rs
+ .sp
+ The unused bits of the \fIoptions\fP argument for \fBpcre_dfa_exec()\fP must be
+ zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_\fIxxx\fP,
+ PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
+ PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE,
+ PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.
+ All but the last four of these are exactly the same as for \fBpcre_exec()\fP,
+ so their description is not repeated here.
+ .sp
+   PCRE_PARTIAL_HARD
+   PCRE_PARTIAL_SOFT
+ .sp
+ These have the same general effect as they do for \fBpcre_exec()\fP, but the
+ details are slightly different. When PCRE_PARTIAL_HARD is set for
+ \fBpcre_dfa_exec()\fP, it returns PCRE_ERROR_PARTIAL if the end of the subject
+ is reached and there is still at least one matching possibility that requires
+ additional characters. This happens even if some complete matches have also
+ been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH
+ is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached,
+ there have been no complete matches, but there is still at least one matching
+ possibility. The portion of the string that was inspected when the longest
+ partial match was found is set as the first matching string in both cases.
+ There is a more detailed discussion of partial and multi-segment matching, with
+ examples, in the
+ .\" HREF
+ \fBpcrepartial\fP
+ .\"
+ documentation.
+ .sp
+   PCRE_DFA_SHORTEST
+ .sp
+ Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as
+ soon as it has found one match. Because of the way the alternative algorithm
+ works, this is necessarily the shortest possible match at the first possible
+ matching point in the subject string.
+ .sp
+   PCRE_DFA_RESTART
+ .sp
+ When \fBpcre_dfa_exec()\fP returns a partial match, it is possible to call it
+ again, with additional subject characters, and have it continue with the same
+ match. The PCRE_DFA_RESTART option requests this action; when it is set, the
+ \fIworkspace\fP and \fIwscount\fP options must reference the same vector as
+ before because data about the match so far is left in them after a partial
+ match. There is more discussion of this facility in the
+ .\" HREF
+ \fBpcrepartial\fP
+ .\"
+ documentation.
+ .
+ .
+ .SS "Successful returns from \fBpcre_dfa_exec()\fP"
+ .rs
+ .sp
+ When \fBpcre_dfa_exec()\fP succeeds, it may have matched more than one
+ substring in the subject. Note, however, that all the matches from one run of
+ the function start at the same point in the subject. The shorter matches are
+ all initial substrings of the longer matches. For example, if the pattern
+ .sp
+   <.*>
+ .sp
+ is matched against the string
+ .sp
+   This is <something> <something else> <something further> no more
+ .sp
+ the three matched strings are
+ .sp
+   <something>
+   <something> <something else>
+   <something> <something else> <something further>
+ .sp
+ On success, the yield of the function is a number greater than zero, which is
+ the number of matched substrings. The substrings themselves are returned in
+ \fIovector\fP. Each string uses two elements; the first is the offset to the
+ start, and the second is the offset to the end. In fact, all the strings have
+ the same start offset. (Space could have been saved by giving this only once,
+ but it was decided to retain some compatibility with the way \fBpcre_exec()\fP
+ returns data, even though the meaning of the strings is different.)
+ .P
+ The strings are returned in reverse order of length; that is, the longest
+ matching string is given first. If there were too many matches to fit into
+ \fIovector\fP, the yield of the function is zero, and the vector is filled with
+ the longest matches.
+ .
+ .
+ .SS "Error returns from \fBpcre_dfa_exec()\fP"
+ .rs
+ .sp
+ The \fBpcre_dfa_exec()\fP function returns a negative number when it fails.
+ Many of the errors are the same as for \fBpcre_exec()\fP, and these are
+ described
+ .\" HTML <a href="#errorlist">
+ .\" </a>
+ above.
+ .\"
+ There are in addition the following errors that are specific to
+ \fBpcre_dfa_exec()\fP:
+ .sp
+   PCRE_ERROR_DFA_UITEM      (-16)
+ .sp
+ This return is given if \fBpcre_dfa_exec()\fP encounters an item in the pattern
+ that it does not support, for instance, the use of \eC or a back reference.
+ .sp
+   PCRE_ERROR_DFA_UCOND      (-17)
+ .sp
+ This return is given if \fBpcre_dfa_exec()\fP encounters a condition item that
+ uses a back reference for the condition, or a test for recursion in a specific
+ group. These are not supported.
+ .sp
+   PCRE_ERROR_DFA_UMLIMIT    (-18)
+ .sp
+ This return is given if \fBpcre_dfa_exec()\fP is called with an \fIextra\fP
+ block that contains a setting of the \fImatch_limit\fP or
+ \fImatch_limit_recursion\fP fields. This is not supported (these fields are
+ meaningless for DFA matching).
+ .sp
+   PCRE_ERROR_DFA_WSSIZE     (-19)
+ .sp
+ This return is given if \fBpcre_dfa_exec()\fP runs out of space in the
+ \fIworkspace\fP vector.
+ .sp
+   PCRE_ERROR_DFA_RECURSE    (-20)
+ .sp
+ When a recursive subpattern is processed, the matching function calls itself
+ recursively, using private vectors for \fIovector\fP and \fIworkspace\fP. This
+ error is given if the output vector is not large enough. This should be
+ extremely rare, as a vector of size 1000 is used.
+ .
+ .
+ .SH "SEE ALSO"
+ .rs
+ .sp
+ \fBpcrebuild\fP(3), \fBpcrecallout\fP(3), \fBpcrecpp(3)\fP(3),
+ \fBpcrematching\fP(3), \fBpcrepartial\fP(3), \fBpcreposix\fP(3),
+ \fBpcreprecompile\fP(3), \fBpcresample\fP(3), \fBpcrestack\fP(3).
+ .
+ .
+ .SH AUTHOR
+ .rs
+ .sp
+ .nf
+ Philip Hazel
+ University Computing Service
+ Cambridge CB2 3QH, England.
+ .fi
+ .
+ .
+ .SH REVISION
+ .rs
+ .sp
+ .nf
+ Last updated: 27 August 2011
+ Copyright (c) 1997-2011 University of Cambridge.
+ .fi

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