PCRE BUILD-TIME OPTIONS
This document describes the optional features of PCRE that can be
- selected when the library is compiled. They are all selected, or dese-
- lected, by providing options to the configure script that is run before
- the make command. The complete list of options for configure (which
- includes the standard ones such as the selection of the installation
- directory) can be obtained by running
+ selected when the library is compiled. It assumes use of the configure
+ script, where the optional features are selected or deselected by pro-
+ viding options to configure before running the make command. However,
+ the same options can be selected in both Unix-like and non-Unix-like
+ environments using the GUI facility of CMakeSetup if you are using
+ CMake instead of configure to build PCRE.
+
+ The complete list of options for configure (which includes the standard
+ ones such as the selection of the installation directory) can be
+ obtained by running
./configure --help
- The following sections include descriptions of options whose names
+ The following sections include descriptions of options whose names
begin with --enable or --disable. These settings specify changes to the
- defaults for the configure command. Because of the way that configure
- works, --enable and --disable always come in pairs, so the complemen-
- tary option always exists as well, but as it specifies the default, it
+ defaults for the configure command. Because of the way that configure
+ works, --enable and --disable always come in pairs, so the complemen-
+ tary option always exists as well, but as it specifies the default, it
is not described.
--enable-utf8
- to the configure command. Of itself, this does not make PCRE treat
- strings as UTF-8. As well as compiling PCRE with this option, you also
- have have to set the PCRE_UTF8 option when you call the pcre_compile()
+ to the configure command. Of itself, this does not make PCRE treat
+ strings as UTF-8. As well as compiling PCRE with this option, you also
+ have have to set the PCRE_UTF8 option when you call the pcre_compile()
function.
UNICODE CHARACTER PROPERTY SUPPORT
- UTF-8 support allows PCRE to process character values greater than 255
- in the strings that it handles. On its own, however, it does not pro-
+ UTF-8 support allows PCRE to process character values greater than 255
+ in the strings that it handles. On its own, however, it does not pro-
vide any facilities for accessing the properties of such characters. If
- you want to be able to use the pattern escapes \P, \p, and \X, which
+ you want to be able to use the pattern escapes \P, \p, and \X, which
refer to Unicode character properties, you must add
--enable-unicode-properties
- to the configure command. This implies UTF-8 support, even if you have
+ to the configure command. This implies UTF-8 support, even if you have
not explicitly requested it.
- Including Unicode property support adds around 30K of tables to the
- PCRE library. Only the general category properties such as Lu and Nd
+ Including Unicode property support adds around 30K of tables to the
+ PCRE library. Only the general category properties such as Lu and Nd
are supported. Details are given in the pcrepattern documentation.
CODE VALUE OF NEWLINE
- By default, PCRE interprets character 10 (linefeed, LF) as indicating
- the end of a line. This is the normal newline character on Unix-like
+ By default, PCRE interprets character 10 (linefeed, LF) as indicating
+ the end of a line. This is the normal newline character on Unix-like
systems. You can compile PCRE to use character 13 (carriage return, CR)
instead, by adding
--enable-newline-is-cr
- to the configure command. There is also a --enable-newline-is-lf
+ to the configure command. There is also a --enable-newline-is-lf
option, which explicitly specifies linefeed as the newline character.
Alternatively, you can specify that line endings are to be indicated by
--enable-newline-is-anycrlf
- which causes PCRE to recognize any of the three sequences CR, LF, or
+ which causes PCRE to recognize any of the three sequences CR, LF, or
CRLF as indicating a line ending. Finally, a fifth option, specified by
--enable-newline-is-any
causes PCRE to recognize any Unicode newline sequence.
- Whatever line ending convention is selected when PCRE is built can be
- overridden when the library functions are called. At build time it is
+ Whatever line ending convention is selected when PCRE is built can be
+ overridden when the library functions are called. At build time it is
conventional to use the standard for your operating system.
+WHAT \R MATCHES
+
+ By default, the sequence \R in a pattern matches any Unicode newline
+ sequence, whatever has been selected as the line ending sequence. If
+ you specify
+
+ --enable-bsr-anycrlf
+
+ the default is changed so that \R matches only CR, LF, or CRLF. What-
+ ever is selected when PCRE is built can be overridden when the library
+ functions are called.
+
+
BUILDING SHARED AND STATIC LIBRARIES
- The PCRE building process uses libtool to build both shared and static
- Unix libraries by default. You can suppress one of these by adding one
+ The PCRE building process uses libtool to build both shared and static
+ Unix libraries by default. You can suppress one of these by adding one
of
--disable-shared
POSIX MALLOC USAGE
When PCRE is called through the POSIX interface (see the pcreposix doc-
- umentation), additional working storage is required for holding the
- pointers to capturing substrings, because PCRE requires three integers
- per substring, whereas the POSIX interface provides only two. If the
+ umentation), additional working storage is required for holding the
+ pointers to capturing substrings, because PCRE requires three integers
+ per substring, whereas the POSIX interface provides only two. If the
number of expected substrings is small, the wrapper function uses space
on the stack, because this is faster than using malloc() for each call.
The default threshold above which the stack is no longer used is 10; it
HANDLING VERY LARGE PATTERNS
- Within a compiled pattern, offset values are used to point from one
- part to another (for example, from an opening parenthesis to an alter-
- nation metacharacter). By default, two-byte values are used for these
- offsets, leading to a maximum size for a compiled pattern of around
- 64K. This is sufficient to handle all but the most gigantic patterns.
- Nevertheless, some people do want to process enormous patterns, so it
- is possible to compile PCRE to use three-byte or four-byte offsets by
+ Within a compiled pattern, offset values are used to point from one
+ part to another (for example, from an opening parenthesis to an alter-
+ nation metacharacter). By default, two-byte values are used for these
+ offsets, leading to a maximum size for a compiled pattern of around
+ 64K. This is sufficient to handle all but the most gigantic patterns.
+ Nevertheless, some people do want to process enormous patterns, so it
+ is possible to compile PCRE to use three-byte or four-byte offsets by
adding a setting such as
--with-link-size=3
- to the configure command. The value given must be 2, 3, or 4. Using
- longer offsets slows down the operation of PCRE because it has to load
+ to the configure command. The value given must be 2, 3, or 4. Using
+ longer offsets slows down the operation of PCRE because it has to load
additional bytes when handling them.
AVOIDING EXCESSIVE STACK USAGE
When matching with the pcre_exec() function, PCRE implements backtrack-
- ing by making recursive calls to an internal function called match().
- In environments where the size of the stack is limited, this can se-
- verely limit PCRE's operation. (The Unix environment does not usually
+ ing by making recursive calls to an internal function called match().
+ In environments where the size of the stack is limited, this can se-
+ verely limit PCRE's operation. (The Unix environment does not usually
suffer from this problem, but it may sometimes be necessary to increase
- the maximum stack size. There is a discussion in the pcrestack docu-
- mentation.) An alternative approach to recursion that uses memory from
- the heap to remember data, instead of using recursive function calls,
- has been implemented to work round the problem of limited stack size.
+ the maximum stack size. There is a discussion in the pcrestack docu-
+ mentation.) An alternative approach to recursion that uses memory from
+ the heap to remember data, instead of using recursive function calls,
+ has been implemented to work round the problem of limited stack size.
If you want to build a version of PCRE that works this way, add
--disable-stack-for-recursion
- to the configure command. With this configuration, PCRE will use the
- pcre_stack_malloc and pcre_stack_free variables to call memory manage-
- ment functions. By default these point to malloc() and free(), but you
+ to the configure command. With this configuration, PCRE will use the
+ pcre_stack_malloc and pcre_stack_free variables to call memory manage-
+ ment functions. By default these point to malloc() and free(), but you
can replace the pointers so that your own functions are used.
- Separate functions are provided rather than using pcre_malloc and
- pcre_free because the usage is very predictable: the block sizes
- requested are always the same, and the blocks are always freed in
- reverse order. A calling program might be able to implement optimized
- functions that perform better than malloc() and free(). PCRE runs
+ Separate functions are provided rather than using pcre_malloc and
+ pcre_free because the usage is very predictable: the block sizes
+ requested are always the same, and the blocks are always freed in
+ reverse order. A calling program might be able to implement optimized
+ functions that perform better than malloc() and free(). PCRE runs
noticeably more slowly when built in this way. This option affects only
- the pcre_exec() function; it is not relevant for the the
+ the pcre_exec() function; it is not relevant for the the
pcre_dfa_exec() function.
LIMITING PCRE RESOURCE USAGE
- Internally, PCRE has a function called match(), which it calls repeat-
- edly (sometimes recursively) when matching a pattern with the
- pcre_exec() function. By controlling the maximum number of times this
- function may be called during a single matching operation, a limit can
- be placed on the resources used by a single call to pcre_exec(). The
- limit can be changed at run time, as described in the pcreapi documen-
- tation. The default is 10 million, but this can be changed by adding a
+ Internally, PCRE has a function called match(), which it calls repeat-
+ edly (sometimes recursively) when matching a pattern with the
+ pcre_exec() function. By controlling the maximum number of times this
+ function may be called during a single matching operation, a limit can
+ be placed on the resources used by a single call to pcre_exec(). The
+ limit can be changed at run time, as described in the pcreapi documen-
+ tation. The default is 10 million, but this can be changed by adding a
setting such as
--with-match-limit=500000
- to the configure command. This setting has no effect on the
+ to the configure command. This setting has no effect on the
pcre_dfa_exec() matching function.
- In some environments it is desirable to limit the depth of recursive
+ In some environments it is desirable to limit the depth of recursive
calls of match() more strictly than the total number of calls, in order
- to restrict the maximum amount of stack (or heap, if --disable-stack-
+ to restrict the maximum amount of stack (or heap, if --disable-stack-
for-recursion is specified) that is used. A second limit controls this;
- it defaults to the value that is set for --with-match-limit, which
- imposes no additional constraints. However, you can set a lower limit
+ it defaults to the value that is set for --with-match-limit, which
+ imposes no additional constraints. However, you can set a lower limit
by adding, for example,
--with-match-limit-recursion=10000
- to the configure command. This value can also be overridden at run
+ to the configure command. This value can also be overridden at run
time.
CREATING CHARACTER TABLES AT BUILD TIME
- PCRE uses fixed tables for processing characters whose code values are
- less than 256. By default, PCRE is built with a set of tables that are
- distributed in the file pcre_chartables.c.dist. These tables are for
+ PCRE uses fixed tables for processing characters whose code values are
+ less than 256. By default, PCRE is built with a set of tables that are
+ distributed in the file pcre_chartables.c.dist. These tables are for
ASCII codes only. If you add
--enable-rebuild-chartables
- to the configure command, the distributed tables are no longer used.
- Instead, a program called dftables is compiled and run. This outputs
+ to the configure command, the distributed tables are no longer used.
+ Instead, a program called dftables is compiled and run. This outputs
the source for new set of tables, created in the default locale of your
C runtime system. (This method of replacing the tables does not work if
- you are cross compiling, because dftables is run on the local host. If
- you need to create alternative tables when cross compiling, you will
+ you are cross compiling, because dftables is run on the local host. If
+ you need to create alternative tables when cross compiling, you will
have to do so "by hand".)
USING EBCDIC CODE
- PCRE assumes by default that it will run in an environment where the
- character code is ASCII (or Unicode, which is a superset of ASCII).
- This is the case for most computer operating systems. PCRE can, how-
+ PCRE assumes by default that it will run in an environment where the
+ character code is ASCII (or Unicode, which is a superset of ASCII).
+ This is the case for most computer operating systems. PCRE can, how-
ever, be compiled to run in an EBCDIC environment by adding
--enable-ebcdic
to the configure command. This setting implies --enable-rebuild-charta-
- bles. You should only use it if you know that you are in an EBCDIC
+ bles. You should only use it if you know that you are in an EBCDIC
environment (for example, an IBM mainframe operating system).
+PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
+
+ By default, pcregrep reads all files as plain text. You can build it so
+ that it recognizes files whose names end in .gz or .bz2, and reads them
+ with libz or libbz2, respectively, by adding one or both of
+
+ --enable-pcregrep-libz
+ --enable-pcregrep-libbz2
+
+ to the configure command. These options naturally require that the rel-
+ evant libraries are installed on your system. Configuration will fail
+ if they are not.
+
+
+PCRETEST OPTION FOR LIBREADLINE SUPPORT
+
+ If you add
+
+ --enable-pcretest-libreadline
+
+ to the configure command, pcretest is linked with the libreadline
+ library, and when its input is from a terminal, it reads it using the
+ readline() function. This provides line-editing and history facilities.
+ Note that libreadline is GPL-licenced, so if you distribute a binary of
+ pcretest linked in this way, there may be licensing issues.
+
+
SEE ALSO
pcreapi(3), pcre_config(3).
REVISION
- Last updated: 30 July 2007
+ Last updated: 18 December 2007
Copyright (c) 1997-2007 University of Cambridge.
------------------------------------------------------------------------------
a Perl-compatible manner. A sample program that demonstrates the sim-
plest way of using them is provided in the file called pcredemo.c in
the source distribution. The pcresample documentation describes how to
- run it.
+ compile and run it.
A second matching function, pcre_dfa_exec(), which is not Perl-compati-
ble, is also provided. This uses a different algorithm for the match-
dollar metacharacters, the handling of #-comments in /x mode, and, when
CRLF is a recognized line ending sequence, the match position advance-
ment for a non-anchored pattern. There is more detail about this in the
- section on pcre_exec() options below. The choice of newline convention
- does not affect the interpretation of the \n or \r escape sequences.
+ section on pcre_exec() options below.
+
+ The choice of newline convention does not affect the interpretation of
+ the \n or \r escape sequences, nor does it affect what \R matches,
+ which is controlled in a similar way, but by separate options.
MULTITHREADING
- The PCRE functions can be used in multi-threading applications, with
+ The PCRE functions can be used in multi-threading applications, with
the proviso that the memory management functions pointed to by
pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
callout function pointed to by pcre_callout, are shared by all threads.
- The compiled form of a regular expression is not altered during match-
+ The compiled form of a regular expression is not altered during match-
ing, so the same compiled pattern can safely be used by several threads
at once.
SAVING PRECOMPILED PATTERNS FOR LATER USE
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
- pcreprecompile documentation. However, compiling a regular expression
- with one version of PCRE for use with a different version is not guar-
+ 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
+ pcreprecompile documentation. However, compiling a regular expression
+ with one version of PCRE for use with a different version is not guar-
anteed to work and may cause crashes.
int pcre_config(int what, void *where);
- The function pcre_config() makes it possible for a PCRE client to dis-
+ The function pcre_config() makes it possible for a PCRE client to dis-
cover which optional features have been compiled into the PCRE library.
- The pcrebuild documentation has more details about these optional fea-
+ The pcrebuild documentation has more details about these optional fea-
tures.
- The first argument for pcre_config() is an integer, specifying which
+ The first argument for pcre_config() 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
+ into which the information is placed. The following information is
available:
PCRE_CONFIG_UTF8
- The output is an integer that is set to one if UTF-8 support is avail-
+ The output is an integer that is set to one if UTF-8 support is avail-
able; otherwise it is set to zero.
PCRE_CONFIG_UNICODE_PROPERTIES
- The output is an integer that is set to one if support for Unicode
+ The output is an integer that is set to one if support for Unicode
character properties is available; otherwise it is set to zero.
PCRE_CONFIG_NEWLINE
- The output is an integer whose value specifies the default character
- sequence that is recognized as meaning "newline". The four values that
+ The output is an integer whose value specifies the default character
+ sequence that is recognized as meaning "newline". The four values that
are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
- and -1 for ANY. The default should normally be the standard sequence
+ and -1 for ANY. The default should normally be the standard sequence
for your operating system.
+ PCRE_CONFIG_BSR
+
+ The output is an integer whose value indicates what character sequences
+ the \R escape sequence matches by default. A value of 0 means that \R
+ matches any Unicode line ending sequence; a value of 1 means that \R
+ matches only CR, LF, or CRLF. The default can be overridden when a pat-
+ tern is compiled or matched.
+
PCRE_CONFIG_LINK_SIZE
- The output is an integer that contains the number of bytes used for
+ 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
+ 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.
PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
- The output is an integer that contains the threshold above which the
- POSIX interface uses malloc() for output vectors. Further details are
+ The output is an integer that contains the threshold above which the
+ POSIX interface uses malloc() for output vectors. Further details are
given in the pcreposix documentation.
PCRE_CONFIG_MATCH_LIMIT
The output is an integer that gives the default limit for the number of
- internal matching function calls in a pcre_exec() execution. Further
+ internal matching function calls in a pcre_exec() execution. Further
details are given with pcre_exec() below.
PCRE_CONFIG_MATCH_LIMIT_RECURSION
- The output is an integer that gives the default limit for the depth of
- recursion when calling the internal matching function in a pcre_exec()
+ The output is an integer that gives the default limit for the depth of
+ recursion when calling the internal matching function in a pcre_exec()
execution. Further details are given with pcre_exec() below.
PCRE_CONFIG_STACKRECURSE
- The output is an integer that is set to one if internal recursion when
+ The output is an integer that is set to one if internal recursion when
running pcre_exec() is implemented by recursive function calls that use
- the stack to remember their state. This is the usual way that PCRE is
+ the stack to remember their state. This is the usual way that PCRE is
compiled. The output is zero if PCRE was compiled to use blocks of data
- on the heap instead of recursive function calls. In this case,
- pcre_stack_malloc and pcre_stack_free are called to manage memory
+ on the heap instead of recursive function calls. In this case,
+ pcre_stack_malloc and pcre_stack_free are called to manage memory
blocks on the heap, thus avoiding the use of the stack.
Either of the functions pcre_compile() or pcre_compile2() can be called
to compile a pattern into an internal form. The only difference between
- the two interfaces is that pcre_compile2() has an additional argument,
+ the two interfaces is that pcre_compile2() has an additional argument,
errorcodeptr, via which a numerical error code can be returned.
The pattern is a C string terminated by a binary zero, and is passed in
- the pattern argument. A pointer to a single block of memory that is
- obtained via pcre_malloc is returned. This contains the compiled code
+ the pattern argument. A pointer to a single block of memory that is
+ obtained via pcre_malloc is returned. This contains the compiled code
and related data. The pcre 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 pcre_free) when it is no
longer required.
- Although the compiled code of a PCRE regex is relocatable, that is, it
+ Although the compiled code of a PCRE regex is relocatable, that is, it
does not depend on memory location, the complete pcre data block is not
- fully relocatable, because it may contain a copy of the tableptr argu-
+ fully relocatable, because it may contain a copy of the tableptr argu-
ment, which is an address (see below).
The options argument contains various bit settings that affect the com-
- pilation. It should be zero if no options are required. The available
- options are described below. Some of them, in particular, those that
- are compatible with Perl, can also be set and unset from within the
- pattern (see the detailed description in the pcrepattern documenta-
- tion). For these options, the contents of the options argument speci-
- fies their initial settings at the start of compilation and execution.
- The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at the time
+ pilation. It should be zero if no options are required. The available
+ options are described below. Some of them, in particular, those that
+ are compatible with Perl, can also be set and unset from within the
+ pattern (see the detailed description in the pcrepattern documenta-
+ tion). For these options, the contents of the options argument speci-
+ fies their initial settings at the start of compilation and execution.
+ The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at the time
of matching as well as at compile time.
If errptr is NULL, pcre_compile() returns NULL immediately. Otherwise,
- if compilation of a pattern fails, pcre_compile() returns NULL, and
+ if compilation of a pattern fails, pcre_compile() returns NULL, and
sets the variable pointed to by errptr to point to a textual error mes-
sage. This is a static string that is part of the library. You must not
try to free it. The offset from the start of the pattern to the charac-
ter where the error was discovered is placed in the variable pointed to
- by erroffset, which must not be NULL. If it is, an immediate error is
+ by erroffset, which must not be NULL. If it is, an immediate error is
given.
- If pcre_compile2() is used instead of pcre_compile(), and the error-
- codeptr 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
+ If pcre_compile2() is used instead of pcre_compile(), and the error-
+ codeptr 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.
- If the final argument, tableptr, is NULL, PCRE uses a default set of
- character tables that are built when PCRE is compiled, using the
- default C locale. Otherwise, tableptr must be an address that is the
- result of a call to pcre_maketables(). This value is stored with the
- compiled pattern, and used again by pcre_exec(), unless another table
+ If the final argument, tableptr, is NULL, PCRE uses a default set of
+ character tables that are built when PCRE is compiled, using the
+ default C locale. Otherwise, tableptr must be an address that is the
+ result of a call to pcre_maketables(). This value is stored with the
+ compiled pattern, and used again by pcre_exec(), unless another table
pointer is passed to it. For more discussion, see the section on locale
support below.
- This code fragment shows a typical straightforward call to pcre_com-
+ This code fragment shows a typical straightforward call to pcre_com-
pile():
pcre *re;
&erroffset, /* for error offset */
NULL); /* use default character tables */
- The following names for option bits are defined in the pcre.h header
+ The following names for option bits are defined in the pcre.h header
file:
PCRE_ANCHORED
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
- that is being searched (the "subject string"). This effect can also be
- achieved by appropriate constructs in the pattern itself, which is the
+ 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.
PCRE_AUTO_CALLOUT
If this bit is set, pcre_compile() automatically inserts callout items,
- all with number 255, before each pattern item. For discussion of the
+ all with number 255, before each pattern item. For discussion of the
callout facility, see the pcrecallout documentation.
+ PCRE_BSR_ANYCRLF
+ PCRE_BSR_UNICODE
+
+ These options (which are mutually exclusive) control what the \R 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 set-
+ ting an option when a compiled pattern is matched.
+
PCRE_CASELESS
- 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. 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 com-
- piled 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
+ 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. 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 com-
+ piled 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.
PCRE_DOLLAR_ENDONLY
- 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 a newline at the end of the string (but not
- before any other newlines). The PCRE_DOLLAR_ENDONLY option is ignored
- if PCRE_MULTILINE is set. There is no equivalent to this option in
+ 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 a newline at the end of the string (but not
+ before any other newlines). The PCRE_DOLLAR_ENDONLY option is ignored
+ if PCRE_MULTILINE is set. There is no equivalent to this option in
Perl, and no way to set it within a pattern.
PCRE_DOTALL
If this bit is set, a dot metacharater in the pattern matches all char-
- acters, including those that indicate newline. Without it, 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
+ acters, including those that indicate newline. Without it, 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
newline characters, independent of the setting of this option.
PCRE_DUPNAMES
- If this bit is set, names used to identify capturing subpatterns need
+ 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
+ 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 pcrepattern documentation.
PCRE_EXTENDED
- If this bit is set, whitespace data characters in the pattern are
+ If this bit is set, whitespace data characters in the pattern are
totally ignored except when escaped or inside a character class. White-
space does not include the VT character (code 11). In addition, charac-
ters between an unescaped # outside a character class and the next new-
- line, inclusive, are also ignored. This is equivalent to Perl's /x
- option, and it can be changed within a pattern by a (?x) option set-
+ line, inclusive, are also ignored. This is equivalent to Perl's /x
+ option, and it can be changed within a pattern by a (?x) option set-
ting.
- 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
+ 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.
PCRE_EXTRA
- 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. (Perl can, however, be persuaded to give a warning for this.)
- There are at present no other features controlled by this option. It
+ 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. (Perl can, however, be persuaded to give a warning for this.)
+ There are at present no other features controlled by this option. It
can also be set by a (?X) option setting within a pattern.
PCRE_FIRSTLINE
- If this option is set, an unanchored pattern is required to match
- before or at the first newline in the subject string, though the
+ 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.
PCRE_MULTILINE
- By default, PCRE treats the subject string as consisting of a single
- line of 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 ($) matches only at the end of
+ By default, PCRE treats the subject string as consisting of a single
+ line of characters (even if it actually contains newlines). The "start
+ of line" metacharacter (^) matches only at the start of the string,
+ while the "end of line" metacharacter ($) 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.
- When PCRE_MULTILINE it is set, the "start of line" and "end of line"
- constructs match immediately following or immediately before internal
- newlines in the subject string, respectively, as well as at the very
- start and end. This is equivalent to Perl's /m option, and it can be
+ When PCRE_MULTILINE it is set, the "start of line" and "end of line"
+ constructs match immediately following or immediately before internal
+ newlines in the subject string, respectively, as well as at the very
+ start and end. This is equivalent to Perl's /m option, and it can be
changed within a pattern by a (?m) option setting. If there are no new-
- lines in a subject string, or no occurrences of ^ or $ in a pattern,
+ lines in a subject string, or no occurrences of ^ or $ in a pattern,
setting PCRE_MULTILINE has no effect.
PCRE_NEWLINE_CR
PCRE_NEWLINE_ANYCRLF
PCRE_NEWLINE_ANY
- 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
+ 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
+ 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
+ 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.
- The newline setting in the options word uses three bits that are
+ 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 sensi-
+ 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 sensi-
ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
- PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers and
+ PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers and
cause an error.
- The only time that a line break is specially recognized when compiling
- a pattern is if PCRE_EXTENDED is set, and an unescaped # outside a
- character class is encountered. This indicates a comment that lasts
- until after the next line break sequence. In other circumstances, line
- break sequences are treated as literal data, except that in
+ The only time that a line break is specially recognized when compiling
+ a pattern is if PCRE_EXTENDED is set, and an unescaped # outside a
+ character class is encountered. This indicates a comment that lasts
+ until after the next line break sequence. In other circumstances, line
+ break sequences are treated as literal data, except that in
PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
and are therefore ignored.
The newline option that is set at compile time becomes the default that
- is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
+ is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
PCRE_NO_AUTO_CAPTURE
If this option is set, it disables the use of numbered capturing paren-
- theses 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).
+ theses 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.
PCRE_UNGREEDY
- 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
+ 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.
PCRE_UTF8
- 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 when PCRE is built to include UTF-8 sup-
- port. If not, the use of this option provokes an error. Details of how
- this option changes the behaviour of PCRE are given in the section on
+ 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 when PCRE is built to include UTF-8 sup-
+ port. If not, the use of this option provokes an error. Details of how
+ this option changes the behaviour of PCRE are given in the section on
UTF-8 support in the main pcre page.
PCRE_NO_UTF8_CHECK
When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
- automatically checked. There is a discussion about the validity of
- UTF-8 strings in the main pcre page. If an invalid UTF-8 sequence of
- bytes is found, pcre_compile() returns an error. If you already know
+ automatically checked. There is a discussion about the validity of
+ UTF-8 strings in the main pcre page. If an invalid UTF-8 sequence of
+ bytes is found, pcre_compile() returns an error. If you already know
that your pattern is valid, and you want to skip this check for perfor-
- mance 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 pcre_exec() and pcre_dfa_exec(), to suppress the
+ mance 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 pcre_exec() and pcre_dfa_exec(), to suppress the
UTF-8 validity checking of subject strings.
COMPILATION ERROR CODES
- The following table lists the error codes than may be returned by
- pcre_compile2(), along with the error messages that may be returned by
- both compiling functions. As PCRE has developed, some error codes have
+ The following table lists the error codes than may be returned by
+ pcre_compile2(), 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.
0 no error
9 nothing to repeat
10 [this code is not in use]
11 internal error: unexpected repeat
- 12 unrecognized character after (?
+ 12 unrecognized character after (? or (?-
13 POSIX named classes are supported only within a class
14 missing )
15 reference to non-existent subpattern
17 unknown option bit(s) set
18 missing ) after comment
19 [this code is not in use]
- 20 regular expression too large
+ 20 regular expression is too large
21 failed to get memory
22 unmatched parentheses
23 internal error: code overflow
46 malformed \P or \p sequence
47 unknown property name after \P or \p
48 subpattern name is too long (maximum 32 characters)
- 49 too many named subpatterns (maximum 10,000)
+ 49 too many named subpatterns (maximum 10000)
50 [this code is not in use]
51 octal value is greater than \377 (not in UTF-8 mode)
52 internal error: overran compiling workspace
- 53 internal error: previously-checked referenced subpattern not
+ 53 internal error: previously-checked referenced subpattern not
found
54 DEFINE group contains more than one branch
55 repeating a DEFINE group is not allowed
- 56 inconsistent NEWLINE options"
+ 56 inconsistent NEWLINE options
57 \g is not followed by a braced name or an optionally braced
non-zero number
58 (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number
+ 59 (*VERB) with an argument is not supported
+ 60 (*VERB) not recognized
+ 61 number is too big
+ 62 subpattern name expected
+ 63 digit expected after (?+
+
+ 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.
STUDYING A PATTERN
Return 1 if the pattern contains any explicit matches for CR or LF
characters, otherwise 0. The fourth argument should point to an int
- variable.
+ variable. An explicit match is either a literal CR or LF character, or
+ \r or \n.
PCRE_INFO_JCHANGED
- Return 1 if the (?J) option setting is used in the pattern, otherwise
- 0. The fourth argument should point to an int variable. The (?J) inter-
- nal option setting changes the local PCRE_DUPNAMES option.
+ Return 1 if the (?J) or (?-J) option setting is used in the pattern,
+ otherwise 0. The fourth argument should point to an int variable. (?J)
+ and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
PCRE_INFO_LASTLITERAL
- Return the value of the rightmost literal byte that must exist in any
- matched string, other than at its start, if such a byte has been
+ Return the value of the rightmost literal byte that must exist in any
+ matched string, other than at its start, if such a byte has been
recorded. The fourth argument should point to an int variable. If there
- is no such byte, -1 is returned. For anchored patterns, a last literal
- byte is recorded only if it follows something of variable length. For
+ is no such byte, -1 is returned. For anchored patterns, a last literal
+ byte is recorded only if it follows something of variable length. For
example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
/^a\dz\d/ the returned value is -1.
PCRE_INFO_NAMEENTRYSIZE
PCRE_INFO_NAMETABLE
- PCRE supports the use of named as well as numbered capturing parenthe-
- ses. The names are just an additional way of identifying the parenthe-
+ PCRE supports the use of named as well as numbered capturing parenthe-
+ ses. The names are just an additional way of identifying the parenthe-
ses, which still acquire numbers. Several convenience functions such as
- pcre_get_named_substring() are provided for extracting captured sub-
- strings by name. It is also possible to extract the data directly, by
- first converting the name to a number in order to access the correct
+ pcre_get_named_substring() are provided for extracting captured sub-
+ strings by name. It is also possible to extract the data directly, by
+ first converting the name to a number in order to access the correct
pointers in the output vector (described with pcre_exec() below). To do
- the conversion, you need to use the name-to-number map, which is
+ the conversion, you need to use the name-to-number map, which is
described by these three values.
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 int 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 char). The
+ of each entry; both of these return an int 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 char). The
first two bytes of each entry are the number of the capturing parenthe-
- sis, most significant byte first. The rest of the entry is the corre-
- sponding name, zero terminated. The names are in alphabetical order.
+ sis, most significant byte first. The rest of the entry is the corre-
+ sponding name, zero terminated. The names are in alphabetical order.
When PCRE_DUPNAMES is set, duplicate names are in order of their paren-
- theses numbers. For example, consider the following pattern (assume
- PCRE_EXTENDED is set, so white space - including newlines - is
+ theses numbers. For example, consider the following pattern (assume
+ PCRE_EXTENDED is set, so white space - including newlines - is
ignored):
(?<date> (?<year>(\d\d)?\d\d) -
(?<month>\d\d) - (?<day>\d\d) )
- 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,
+ 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 hexadecimal, and undefined bytes shown
as ??:
00 04 m o n t h 00
00 02 y e a r 00 ??
- When writing code to extract data from named subpatterns using the
- name-to-number map, remember that the length of the entries is likely
+ When writing code to extract data from named subpatterns using the
+ name-to-number map, remember that the length of the entries is likely
to be different for each compiled pattern.
PCRE_INFO_OKPARTIAL
- Return 1 if the pattern can be used for partial matching, otherwise 0.
- The fourth argument should point to an int variable. The pcrepartial
- documentation lists the restrictions that apply to patterns when par-
+ Return 1 if the pattern can be used for partial matching, otherwise 0.
+ The fourth argument should point to an int variable. The pcrepartial
+ documentation lists the restrictions that apply to patterns when par-
tial matching is used.
PCRE_INFO_OPTIONS
- Return a copy of the options with which the pattern was compiled. The
- fourth argument should point to an unsigned long int variable. These
+ Return a copy of the options with which the pattern was compiled. The
+ fourth argument should point to an unsigned long int variable. These
option bits are those specified in the call to pcre_compile(), modified
by any 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,
+ 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.
- A pattern is automatically anchored by PCRE if all of its top-level
+ A pattern is automatically anchored by PCRE if all of its top-level
alternatives begin with one of the following:
^ unless PCRE_MULTILINE is set
PCRE_INFO_SIZE
- Return the size of the compiled pattern, that is, the value that was
+ Return the size of the compiled pattern, that is, the value that was
passed as the argument to pcre_malloc() when PCRE was getting memory in
which to place the compiled data. The fourth argument should point to a
size_t variable.
PCRE_INFO_STUDYSIZE
Return the size of the data block pointed to by the study_data field in
- a pcre_extra block. That is, it is the value that was passed to
+ a pcre_extra block. That is, it is the value that was passed to
pcre_malloc() when PCRE was getting memory into which to place the data
- created by pcre_study(). The fourth argument should point to a size_t
+ created by pcre_study(). The fourth argument should point to a size_t
variable.
int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
- The pcre_info() function is now obsolete because its interface is too
- restrictive to return all the available data about a compiled pattern.
- New programs should use pcre_fullinfo() instead. The yield of
- pcre_info() is the number of capturing subpatterns, or one of the fol-
+ The pcre_info() function is now obsolete because its interface is too
+ restrictive to return all the available data about a compiled pattern.
+ New programs should use pcre_fullinfo() instead. The yield of
+ pcre_info() is the number of capturing subpatterns, or one of the fol-
lowing negative numbers:
PCRE_ERROR_NULL the argument code was NULL
PCRE_ERROR_BADMAGIC the "magic number" was not found
- If the optptr argument is not NULL, a copy of the options with which
- the pattern was compiled is placed in the integer it points to (see
+ If the optptr 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).
- If the pattern is not anchored and the firstcharptr argument is not
- NULL, it is used to pass back information about the first character of
+ If the pattern is not anchored and the firstcharptr argument is not
+ NULL, it is used to pass back information about the first character of
any matched string (see PCRE_INFO_FIRSTBYTE above).
int pcre_refcount(pcre *code, int adjust);
- The pcre_refcount() function is used to maintain a reference count in
+ The pcre_refcount() 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,
+ 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.
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 adjust value (which may be positive or negative) to it. The
+ zero. It is changed only by calling this function, whose action is to
+ add the adjust 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 constrained to lie between 0 and 65535, inclusive. If the new value
is outside these limits, it is forced to the appropriate limit value.
- 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
+ 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.)
const char *subject, int length, int startoffset,
int options, int *ovector, int ovecsize);
- The function pcre_exec() is called to match a subject string against a
- compiled pattern, which is passed in the code argument. If the pattern
+ The function pcre_exec() is called to match a subject string against a
+ compiled pattern, which is passed in the code argument. If the pattern
has been studied, the result of the study should be passed in the extra
- argument. This function is the main matching facility of the library,
+ argument. This function is the main matching facility of the library,
and it operates in a Perl-like manner. For specialist use there is also
- an alternative matching function, which is described below in the sec-
+ an alternative matching function, which is described below in the sec-
tion about the pcre_dfa_exec() function.
- In most applications, the pattern will have been compiled (and option-
- ally studied) in the same process that calls pcre_exec(). However, it
+ In most applications, the pattern will have been compiled (and option-
+ ally studied) in the same process that calls pcre_exec(). 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
+ later in different processes, possibly even on different hosts. For a
discussion about this, see the pcreprecompile documentation.
Here is an example of a simple call to pcre_exec():
Extra data for pcre_exec()
- If the extra argument is not NULL, it must point to a pcre_extra data
- block. The pcre_study() function returns such a block (when it doesn't
- return NULL), but you can also create one for yourself, and pass addi-
- tional information in it. The pcre_extra block contains the following
+ If the extra argument is not NULL, it must point to a pcre_extra data
+ block. The pcre_study() function returns such a block (when it doesn't
+ return NULL), but you can also create one for yourself, and pass addi-
+ tional information in it. The pcre_extra block contains the following
fields (not necessarily in this order):
unsigned long int flags;
void *callout_data;
const unsigned char *tables;
- The flags field is a bitmap that specifies which of the other fields
+ The flags field is a bitmap that specifies which of the other fields
are set. The flag bits are:
PCRE_EXTRA_STUDY_DATA
PCRE_EXTRA_CALLOUT_DATA
PCRE_EXTRA_TABLES
- Other flag bits should be set to zero. The study_data field is set in
- the pcre_extra block that is returned by pcre_study(), together with
+ Other flag bits should be set to zero. The study_data field is set in
+ the pcre_extra block that is returned by pcre_study(), together with
the appropriate flag bit. You should not set this yourself, but you may
- add to the block by setting the other fields and their corresponding
+ add to the block by setting the other fields and their corresponding
flag bits.
The match_limit 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
+ 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 function called match() which it calls repeat-
- edly (sometimes recursively). The limit set by match_limit is imposed
- on the number of times this function is called during a match, which
- has the effect of limiting the amount of backtracking that can take
+ Internally, PCRE uses a function called match() which it calls repeat-
+ edly (sometimes recursively). The limit set by match_limit is imposed
+ on the number of times this function is called during a match, which
+ 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 in the subject string.
- 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 override the default by suppling pcre_exec() with a
- pcre_extra block in which match_limit is set, and
- PCRE_EXTRA_MATCH_LIMIT is set in the flags field. If the limit is
+ 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 override the default by suppling pcre_exec() with a
+ pcre_extra block in which match_limit is set, and
+ PCRE_EXTRA_MATCH_LIMIT is set in the flags field. If the limit is
exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
- The match_limit_recursion field is similar to match_limit, but instead
+ The match_limit_recursion field is similar to match_limit, but instead
of limiting the total number of times that match() is called, it limits
- the depth of recursion. The recursion depth is a smaller number than
- the total number of calls, because not all calls to match() are recur-
+ the depth of recursion. The recursion depth is a smaller number than
+ the total number of calls, because not all calls to match() are recur-
sive. This limit is of use only if it is set smaller than match_limit.
- Limiting the recursion depth limits the amount of stack that can be
+ Limiting the recursion depth limits the amount of stack that can be
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.
- The default value for match_limit_recursion can be set when PCRE is
- built; the default default is the same value as the default for
- match_limit. You can override the default by suppling pcre_exec() with
- a pcre_extra block in which match_limit_recursion is set, and
- PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the flags field. If the
+ The default value for match_limit_recursion can be set when PCRE is
+ built; the default default is the same value as the default for
+ match_limit. You can override the default by suppling pcre_exec() with
+ a pcre_extra block in which match_limit_recursion is set, and
+ PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the flags field. If the
limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
- The pcre_callout field is used in conjunction with the "callout" fea-
+ The pcre_callout field is used in conjunction with the "callout" fea-
ture, which is described in the pcrecallout documentation.
- The tables field is used to pass a character tables pointer to
- pcre_exec(); 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 pcre_compile() via its tableptr argu-
+ The tables field is used to pass a character tables pointer to
+ pcre_exec(); 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 pcre_compile() via its tableptr argu-
ment. If NULL is passed to pcre_exec() 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 pcre_exec() is called. See the pcreprecompile documenta-
+ 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 pcre_exec() is called. See the pcreprecompile documenta-
tion for a discussion of saving compiled patterns for later use.
Option bits for pcre_exec()
- The unused bits of the options argument for pcre_exec() must be zero.
- The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
+ The unused bits of the options argument for pcre_exec() must be zero.
+ The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and
PCRE_PARTIAL.
PCRE_ANCHORED
- The PCRE_ANCHORED option limits pcre_exec() 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
+ The PCRE_ANCHORED option limits pcre_exec() 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.
+ PCRE_BSR_ANYCRLF
+ PCRE_BSR_UNICODE
+
+ These options (which are mutually exclusive) control what the \R 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.
+
PCRE_NEWLINE_CR
PCRE_NEWLINE_LF
PCRE_NEWLINE_CRLF
When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is
set, and a match attempt for an unanchored pattern fails when the cur-
rent position is at a CRLF sequence, and the pattern contains no
- explicit matches for CR or NL characters, the match position is
+ 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.
failing at the start, it skips both the CR and the LF before retrying.
However, the pattern [\r\n]A does match that string, because it con-
tains an explicit CR or LF reference, and so advances only by one char-
- acter after the first failure. Note than an explicit CR or LF refer-
- ence occurs for negated character classes such as [^X] because they can
- match CR or LF characters.
+ acter after the first failure.
+
+ An explicit match for CR of LF is either a literal appearance of one of
+ those characters, or one of the \r or \n escape sequences. Implicit
+ matches such as [^X] do not count, nor does \s (which includes CR and
+ LF in the characters that it matches).
- Notwithstanding the above, anomalous effects may still occur when CRLF
+ Notwithstanding the above, anomalous effects may still occur when CRLF
is a valid newline sequence and explicit \r or \n escapes appear in the
pattern.
PCRE_NOTBOL
This option specifies that first character of the subject string is not
- the beginning of a line, so the circumflex metacharacter should not
- match before it. Setting this without PCRE_MULTILINE (at compile time)
- causes circumflex never to match. This option affects only the behav-
+ the beginning of a line, so the circumflex metacharacter should not
+ match before it. Setting this without PCRE_MULTILINE (at compile time)
+ causes circumflex never to match. This option affects only the behav-
iour of the circumflex metacharacter. It does not affect \A.
PCRE_NOTEOL
This option specifies that the end of the subject string is not the end
- of a line, so the dollar metacharacter should not match it nor (except
- in multiline mode) a newline immediately before it. Setting this with-
+ of a line, so the dollar metacharacter should not match it nor (except
+ in multiline mode) a newline immediately before it. Setting this with-
out PCRE_MULTILINE (at compile time) causes dollar never to match. This
- option affects only the behaviour of the dollar metacharacter. It does
+ option affects only the behaviour of the dollar metacharacter. It does
not affect \Z or \z.
PCRE_NOTEMPTY
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
+ 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
a?b?
- is applied to a string not beginning with "a" or "b", it matches the
- empty string at the start of the subject. With PCRE_NOTEMPTY set, this
+ is applied to a string not beginning with "a" or "b", it matches the
+ 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 occur-
rences of "a" or "b".
Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-
- cial case of a pattern match of the empty string within its split()
- function, and when using the /g modifier. It is possible to emulate
+ cial case of a pattern match of the empty string within its split()
+ function, and when using the /g modifier. It is possible to emulate
Perl's behaviour after matching a null string by first trying the match
again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then
- if that fails by advancing the starting offset (see below) and trying
+ 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 the pcredemo.c sample program.
PCRE_NO_UTF8_CHECK
When PCRE_UTF8 is set at compile time, the validity of the subject as a
- UTF-8 string is automatically checked when pcre_exec() is subsequently
- called. The value of startoffset 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 section on UTF-8 support in the
- main pcre page. If an invalid UTF-8 sequence of bytes is found,
- pcre_exec() returns the error PCRE_ERROR_BADUTF8. If startoffset con-
+ UTF-8 string is automatically checked when pcre_exec() is subsequently
+ called. The value of startoffset 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 section on UTF-8 support in the
+ main pcre page. If an invalid UTF-8 sequence of bytes is found,
+ pcre_exec() returns the error PCRE_ERROR_BADUTF8. If startoffset con-
tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
- 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 pcre_exec(). You might want to
- do this for the second and subsequent calls to pcre_exec() 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 startoffset
- points to the start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is
- set, the effect of passing an invalid UTF-8 string as a subject, or a
- value of startoffset that does not point to the start of a UTF-8 char-
+ 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 pcre_exec(). You might want to
+ do this for the second and subsequent calls to pcre_exec() 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 startoffset
+ points to the start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is
+ set, the effect of passing an invalid UTF-8 string as a subject, or a
+ value of startoffset that does not point to the start of a UTF-8 char-
acter, is undefined. Your program may crash.
PCRE_PARTIAL
- This option turns on the partial matching feature. If the subject
- string fails to match the pattern, but at some point during the match-
- ing process the end of the subject was reached (that is, the subject
- partially matches the pattern and the failure to match occurred only
- because there were not enough subject characters), pcre_exec() returns
- PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is
- used, there are restrictions on what may appear in the pattern. These
+ This option turns on the partial matching feature. If the subject
+ string fails to match the pattern, but at some point during the match-
+ ing process the end of the subject was reached (that is, the subject
+ partially matches the pattern and the failure to match occurred only
+ because there were not enough subject characters), pcre_exec() returns
+ PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is
+ used, there are restrictions on what may appear in the pattern. These
are discussed in the pcrepartial documentation.
The string to be matched by pcre_exec()
- The subject string is passed to pcre_exec() as a pointer in subject, a
- length in length, and a starting byte offset in startoffset. In UTF-8
- mode, the byte offset must point to the start of a UTF-8 character.
- Unlike the pattern string, the subject may contain binary zero bytes.
- When the starting offset is zero, the search for a match starts at the
+ The subject string is passed to pcre_exec() as a pointer in subject, a
+ length in length, and a starting byte offset in startoffset. In UTF-8
+ mode, the byte offset must point to the start of a UTF-8 character.
+ Unlike the pattern string, the subject may contain binary zero bytes.
+ 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.
- A non-zero starting offset is useful when searching for another match
- in the same subject by calling pcre_exec() again after a previous suc-
- cess. Setting startoffset differs from just passing over a shortened
- string and setting PCRE_NOTBOL in the case of a pattern that begins
+ A non-zero starting offset is useful when searching for another match
+ in the same subject by calling pcre_exec() again after a previous suc-
+ cess. Setting startoffset 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
\Biss\B
- which finds occurrences of "iss" in the middle of words. (\B matches
- only if the current position in the subject is not a word boundary.)
- When applied to the string "Mississipi" the first call to pcre_exec()
- finds the first occurrence. If pcre_exec() is called again with just
- the remainder of the subject, namely "issipi", it does not match,
+ which finds occurrences of "iss" in the middle of words. (\B matches
+ only if the current position in the subject is not a word boundary.)
+ When applied to the string "Mississipi" the first call to pcre_exec()
+ finds the first occurrence. If pcre_exec() is called again with just
+ the remainder of the subject, namely "issipi", it does not match,
because \B is always false at the start of the subject, which is deemed
- to be a word boundary. However, if pcre_exec() is passed the entire
+ to be a word boundary. However, if pcre_exec() is passed the entire
string again, but with startoffset set to 4, it finds the second occur-
- rence of "iss" because it is able to look behind the starting point to
+ rence of "iss" because it is able to look behind the starting point to
discover that it is preceded by a letter.
- If a non-zero starting offset is passed when the pattern is anchored,
+ If a non-zero starting offset is passed when the pattern is anchored,
one 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
+ if the pattern does not require the match to be at the start of the
subject.
How pcre_exec() returns captured substrings
- 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 sub-
- string. PCRE supports several other kinds of parenthesized subpattern
+ 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 sub-
+ string. PCRE supports several other kinds of parenthesized subpattern
that do not cause substrings to be captured.
- Captured substrings are returned to the caller via a vector of integer
- offsets whose address is passed in ovector. The number of elements in
- the vector is passed in ovecsize, which must be a non-negative number.
+ Captured substrings are returned to the caller via a vector of integer
+ offsets whose address is passed in ovector. The number of elements in
+ the vector is passed in ovecsize, which must be a non-negative number.
Note: this argument is NOT the size of ovector in bytes.
- The first two-thirds of the vector is used to pass back captured sub-
- strings, each substring using a pair of integers. The remaining third
- of the vector is used as workspace by pcre_exec() while matching cap-
- turing subpatterns, and is not available for passing back information.
- The length passed in ovecsize should always be a multiple of three. If
+ The first two-thirds of the vector is used to pass back captured sub-
+ strings, each substring using a pair of integers. The remaining third
+ of the vector is used as workspace by pcre_exec() while matching cap-
+ turing subpatterns, and is not available for passing back information.
+ The length passed in ovecsize should always be a multiple of three. If
it is not, it is rounded down.
- When a match is successful, information about captured substrings is
- returned in pairs of integers, starting at the beginning of ovector,
- and continuing up to two-thirds of its length at the most. The first
+ When a match is successful, information about captured substrings is
+ returned in pairs of integers, starting at the beginning of ovector,
+ and continuing up to two-thirds of its length at the most. The first
element of a pair is set to the offset of the first character in a sub-
- string, and the second is set to the offset of the first character
- after the end of a substring. The first pair, ovector[0] and ovec-
- tor[1], identify the portion of the subject string matched by the
- entire pattern. The next pair is used for the first capturing subpat-
+ string, and the second is set to the offset of the first character
+ after the end of a substring. The first pair, ovector[0] and ovec-
+ tor[1], identify the portion of the subject string matched by the
+ entire pattern. The next pair is used for the first capturing subpat-
tern, and so on. The value returned by pcre_exec() is one more than the
highest numbered pair that has been set. For example, if two substrings
- have been captured, the returned value is 3. If there are no capturing
- subpatterns, the return value from a successful match is 1, indicating
+ have been captured, the returned value is 3. If there are no capturing
+ subpatterns, the return value from a successful match is 1, indicating
that just the first pair of offsets has been set.
If a capturing subpattern is matched repeatedly, it is the last portion
of the string that it matched that is returned.
- If the vector is too small to hold all the captured substring offsets,
+ If the vector is too small to hold all the captured substring offsets,
it is used as far as possible (up to two-thirds of its length), and the
- function returns a value of zero. In particular, if the substring off-
+ function returns a value of zero. In particular, if the substring off-
sets are not of interest, pcre_exec() may be called with ovector passed
- as NULL and ovecsize as zero. However, if the pattern contains back
- references and the ovector is not big enough to remember the related
- substrings, PCRE has to get additional memory for use during matching.
+ as NULL and ovecsize as zero. However, if the pattern contains back
+ references and the ovector is not big enough to remember the related
+ substrings, PCRE has to get additional memory for use during matching.
Thus it is usually advisable to supply an ovector.
- The pcre_info() function can be used to find out how many capturing
- subpatterns there are in a compiled pattern. The smallest size for
- ovector that will allow for n captured substrings, in addition to the
+ The pcre_info() function can be used to find out how many capturing
+ subpatterns there are in a compiled pattern. The smallest size for
+ ovector that will allow for n captured substrings, in addition to the
offsets of the substring matched by the whole pattern, is (n+1)*3.
- It is possible for capturing subpattern number n+1 to match some part
+ It is possible for capturing subpattern number n+1 to match some part
of the subject when subpattern n has not been used at all. For example,
- if the string "abc" is matched against the pattern (a|(z))(bc) the
+ 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 corre-
+ 2 is not. When this happens, both values in the offset pairs corre-
sponding to unused subpatterns are set to -1.
- 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
+ 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. However, you can refer to the offsets
- for the second and third capturing subpatterns if you wish (assuming
+ for the second and third capturing subpatterns if you wish (assuming
the vector is large enough, of course).
- Some convenience functions are provided for extracting the captured
+ Some convenience functions are provided for extracting the captured
substrings as separate strings. These are described below.
Error return values from pcre_exec()
- If pcre_exec() fails, it returns a negative number. The following are
+ If pcre_exec() fails, it returns a negative number. The following are
defined in the header file:
PCRE_ERROR_NOMATCH (-1)
PCRE_ERROR_NULL (-2)
- Either code or subject was passed as NULL, or ovector was NULL and
+ Either code or subject was passed as NULL, or ovector was NULL and
ovecsize was not zero.
PCRE_ERROR_BADOPTION (-3)
PCRE_ERROR_BADMAGIC (-4)
- PCRE stores a 4-byte "magic number" at the start of the compiled code,
+ 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 and to detect when a
pattern that was compiled in an environment of one endianness is run in
- an environment with the other endianness. This is the error that PCRE
+ an environment with the other endianness. This is the error that PCRE
gives when the magic number is not present.
PCRE_ERROR_UNKNOWN_OPCODE (-5)
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
+ compiled pattern. This error could be caused by a bug in PCRE or by
overwriting of the compiled pattern.
PCRE_ERROR_NOMEMORY (-6)
- If a pattern contains back references, but the ovector that is passed
+ If a pattern contains back references, but the ovector that is passed
to pcre_exec() 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 pcre_malloc() fails, this error is given. The
+ PCRE gets a block of memory at the start of matching to use for this
+ purpose. If the call via pcre_malloc() fails, this error is given. The
memory is automatically freed at the end of matching.
PCRE_ERROR_NOSUBSTRING (-7)
- This error is used by the pcre_copy_substring(), pcre_get_substring(),
+ This error is used by the pcre_copy_substring(), pcre_get_substring(),
and pcre_get_substring_list() functions (see below). It is never
returned by pcre_exec().
PCRE_ERROR_MATCHLIMIT (-8)
- The backtracking limit, as specified by the match_limit field in a
- pcre_extra structure (or defaulted) was reached. See the description
+ The backtracking limit, as specified by the match_limit field in a
+ pcre_extra structure (or defaulted) was reached. See the description
above.
PCRE_ERROR_CALLOUT (-9)
This error is never generated by pcre_exec() itself. It is provided for
- use by callout functions that want to yield a distinctive error code.
+ use by callout functions that want to yield a distinctive error code.
See the pcrecallout documentation for details.
PCRE_ERROR_BADUTF8 (-10)
- A string that contains an invalid UTF-8 byte sequence was passed as a
+ A string that contains an invalid UTF-8 byte sequence was passed as a
subject.
PCRE_ERROR_BADUTF8_OFFSET (-11)
The UTF-8 byte sequence that was passed as a subject was valid, but the
- value of startoffset did not point to the beginning of a UTF-8 charac-
+ value of startoffset did not point to the beginning of a UTF-8 charac-
ter.
PCRE_ERROR_PARTIAL (-12)
- The subject string did not match, but it did match partially. See the
+ The subject string did not match, but it did match partially. See the
pcrepartial documentation for details of partial matching.
PCRE_ERROR_BADPARTIAL (-13)
- The PCRE_PARTIAL option was used with a compiled pattern containing
- items that are not supported for partial matching. See the pcrepartial
+ The PCRE_PARTIAL option was used with a compiled pattern containing
+ items that are not supported for partial matching. See the pcrepartial
documentation for details of partial matching.
PCRE_ERROR_INTERNAL (-14)
- An unexpected internal error has occurred. This error could be caused
+ An unexpected internal error has occurred. This error could be caused
by a bug in PCRE or by overwriting of the compiled pattern.
PCRE_ERROR_BADCOUNT (-15)
- This error is given if the value of the ovecsize argument is negative.
+ This error is given if the value of the ovecsize argument is negative.
PCRE_ERROR_RECURSIONLIMIT (-21)
The internal recursion limit, as specified by the match_limit_recursion
- field in a pcre_extra structure (or defaulted) was reached. See the
+ field in a pcre_extra structure (or defaulted) was reached. See the
description above.
PCRE_ERROR_BADNEWLINE (-23)
int pcre_get_substring_list(const char *subject,
int *ovector, int stringcount, const char ***listptr);
- Captured substrings can be accessed directly by using the offsets
- returned by pcre_exec() in ovector. For convenience, the functions
+ Captured substrings can be accessed directly by using the offsets
+ returned by pcre_exec() in ovector. For convenience, the functions
pcre_copy_substring(), pcre_get_substring(), and pcre_get_sub-
- string_list() 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
+ string_list() 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 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 pcre_copy_substring() and pcre_get_sub-
+ 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 pcre_copy_substring() and pcre_get_sub-
string(). Unfortunately, the interface to pcre_get_substring_list() is
- not adequate for handling strings containing binary zeros, because the
+ not adequate for handling strings containing binary zeros, because the
end of the final string is not independently indicated.
- The first three arguments are the same for all three of these func-
- tions: subject is the subject string that has just been successfully
+ The first three arguments are the same for all three of these func-
+ tions: subject is the subject string that has just been successfully
matched, ovector is a pointer to the vector of integer offsets that was
passed to pcre_exec(), and stringcount is the number of substrings that
- were captured by the match, including the substring that matched the
+ were captured by the match, including the substring that matched the
entire regular expression. This is the value returned by pcre_exec() if
- it is greater than zero. If pcre_exec() returned zero, indicating that
- it ran out of space in ovector, the value passed as stringcount should
+ it is greater than zero. If pcre_exec() returned zero, indicating that
+ it ran out of space in ovector, the value passed as stringcount should
be the number of elements in the vector divided by three.
- The functions pcre_copy_substring() and pcre_get_substring() extract a
- single substring, whose number is given as stringnumber. A value of
- zero extracts the substring that matched the entire pattern, whereas
- higher values extract the captured substrings. For pcre_copy_sub-
- string(), the string is placed in buffer, whose length is given by
- buffersize, while for pcre_get_substring() a new block of memory is
- obtained via pcre_malloc, and its address is returned via stringptr.
- The yield of the function is the length of the string, not including
+ The functions pcre_copy_substring() and pcre_get_substring() extract a
+ single substring, whose number is given as stringnumber. A value of
+ zero extracts the substring that matched the entire pattern, whereas
+ higher values extract the captured substrings. For pcre_copy_sub-
+ string(), the string is placed in buffer, whose length is given by
+ buffersize, while for pcre_get_substring() a new block of memory is
+ obtained via pcre_malloc, and its address is returned via stringptr.
+ The yield of the function is the length of the string, not including
the terminating zero, or one of these error codes:
PCRE_ERROR_NOMEMORY (-6)
- The buffer was too small for pcre_copy_substring(), or the attempt to
+ The buffer was too small for pcre_copy_substring(), or the attempt to
get memory failed for pcre_get_substring().
PCRE_ERROR_NOSUBSTRING (-7)
There is no substring whose number is stringnumber.
- The pcre_get_substring_list() function extracts all available sub-
- strings and builds a list of pointers to them. All this is done in a
+ The pcre_get_substring_list() function extracts all available sub-
+ strings and builds a list of pointers to them. All this is done in a
single block of memory that is obtained via pcre_malloc. The address of
- the memory block is returned via listptr, 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 the
+ the memory block is returned via listptr, 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 the
error code
PCRE_ERROR_NOMEMORY (-6)
if the attempt to get the memory block failed.
- When any of these functions encounter a substring that is unset, which
- can happen when capturing subpattern number n+1 matches some part of
- the subject, but subpattern n has not been used at all, they return an
+ When any of these functions encounter a substring that is unset, which
+ can happen when capturing subpattern number n+1 matches some part of
+ the subject, but subpattern n has not been used at all, they return an
empty string. This can be distinguished from a genuine zero-length sub-
- string by inspecting the appropriate offset in ovector, which is nega-
+ string by inspecting the appropriate offset in ovector, which is nega-
tive for unset substrings.
- The two convenience functions pcre_free_substring() and pcre_free_sub-
- string_list() can be used to free the memory returned by a previous
+ The two convenience functions pcre_free_substring() and pcre_free_sub-
+ string_list() can be used to free the memory returned by a previous
call of pcre_get_substring() or pcre_get_substring_list(), respec-
- tively. They do nothing more than call the function pointed to by
- pcre_free, which of course could be called directly from a C program.
- However, PCRE is used in some situations where it is linked via a spe-
- cial interface to another programming language that cannot use
- pcre_free directly; it is for these cases that the functions are pro-
+ tively. They do nothing more than call the function pointed to by
+ pcre_free, which of course could be called directly from a C program.
+ However, PCRE is used in some situations where it is linked via a spe-
+ cial interface to another programming language that cannot use
+ pcre_free directly; it is for these cases that the functions are pro-
vided.
int stringcount, const char *stringname,
const char **stringptr);
- To extract a substring by name, you first have to find associated num-
+ To extract a substring by name, you first have to find associated num-
ber. For example, for this pattern
(a+)b(?<xxx>\d+)...
be unique (PCRE_DUPNAMES was not set), you can find the number from the
name by calling pcre_get_stringnumber(). The first argument is the com-
piled pattern, and the second is the name. The yield of the function is
- the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no
+ the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no
subpattern of that name.
Given the number, you can extract the substring directly, or use one of
the functions described in the previous section. For convenience, there
are also two functions that do the whole job.
- Most of the arguments of pcre_copy_named_substring() and
- pcre_get_named_substring() 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
+ Most of the arguments of pcre_copy_named_substring() and
+ pcre_get_named_substring() 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:
- First, instead of a substring number, a substring name is given. Sec-
+ First, instead of a substring number, a substring name is given. Sec-
ond, 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
+ to the compiled pattern. This is needed in order to gain access to the
name-to-number translation table.
- These functions call pcre_get_stringnumber(), and if it succeeds, they
- then call pcre_copy_substring() or pcre_get_substring(), as appropri-
- ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate names, the
+ These functions call pcre_get_stringnumber(), and if it succeeds, they
+ then call pcre_copy_substring() or pcre_get_substring(), as appropri-
+ ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate names, the
behaviour may not be what you want (see the next section).
int pcre_get_stringtable_entries(const pcre *code,
const char *name, char **first, char **last);
- When a pattern is compiled with the PCRE_DUPNAMES option, names for
- subpatterns are not required to be unique. 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 pcrepattern docu-
+ When a pattern is compiled with the PCRE_DUPNAMES option, names for
+ subpatterns are not required to be unique. 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 pcrepattern docu-
mentation.
- When duplicates are present, pcre_copy_named_substring() and
- pcre_get_named_substring() 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 pcre_get_stringnumber()
- function returns one of the numbers that are associated with the name,
+ When duplicates are present, pcre_copy_named_substring() and
+ pcre_get_named_substring() 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 pcre_get_stringnumber()
+ function returns one of the numbers that are associated with the name,
but it is not defined which it is.
- If you want to get full details of all captured substrings for a given
- name, you must use the pcre_get_stringtable_entries() function. The
+ If you want to get full details of all captured substrings for a given
+ name, you must use the pcre_get_stringtable_entries() 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
+ 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 sec-
- tion entitled Information about a pattern. Given all the relevant
- entries for the name, you can extract each of their numbers, and hence
+ 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 sec-
+ tion entitled Information about a pattern. Given all the relevant
+ entries for the name, you can extract each of their numbers, and hence
the captured data, if any.
FINDING ALL POSSIBLE MATCHES
- The traditional matching function uses a similar algorithm to Perl,
+ 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
+ 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 pcrecallout documen-
tation.
What you have to do is to insert a callout right at the end of the pat-
- tern. When your callout function is called, extract and save the cur-
- rent matched substring. Then return 1, which forces pcre_exec() to
- backtrack and try other alternatives. Ultimately, when it runs out of
+ tern. When your callout function is called, extract and save the cur-
+ rent matched substring. Then return 1, which forces pcre_exec() to
+ backtrack and try other alternatives. Ultimately, when it runs out of
matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
int options, int *ovector, int ovecsize,
int *workspace, int wscount);
- The function pcre_dfa_exec() 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. Never-
- theless, there are times when this kind of matching can be useful. For
+ The function pcre_dfa_exec() 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. Never-
+ theless, there are times when this kind of matching can be useful. For
a discussion of the two matching algorithms, see the pcrematching docu-
mentation.
- The arguments for the pcre_dfa_exec() function are the same as for
+ The arguments for the pcre_dfa_exec() function are the same as for
pcre_exec(), plus two extras. The ovector argument is used in a differ-
- ent way, and this is described below. The other common arguments are
- used in the same way as for pcre_exec(), so their description is not
+ ent way, and this is described below. The other common arguments are
+ used in the same way as for pcre_exec(), so their description is not
repeated here.
- The two additional arguments provide workspace for the function. The
- workspace vector should contain at least 20 elements. It is used for
+ 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
+ workspace will be needed for patterns and subjects where there are a
lot of potential matches.
Here is an example of a simple call to pcre_dfa_exec():
Option bits for pcre_dfa_exec()
- The unused bits of the options argument for pcre_dfa_exec() must be
- zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEW-
- LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,
+ The unused bits of the options argument for pcre_dfa_exec() must be
+ zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEW-
+ LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,
PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last
three of these are the same as for pcre_exec(), so their description is
not repeated here.
PCRE_PARTIAL
- This has the same general effect as it does for pcre_exec(), but the
- details are slightly different. When PCRE_PARTIAL is set for
- pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is converted into
- PCRE_ERROR_PARTIAL if the end of the subject is reached, there have
+ This has the same general effect as it does for pcre_exec(), but the
+ details are slightly different. When PCRE_PARTIAL is set for
+ pcre_dfa_exec(), 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 pos-
- sibility. The portion of the string that provided the partial match is
+ sibility. The portion of the string that provided the partial match is
set as the first matching string.
PCRE_DFA_SHORTEST
- Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to
+ 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 alterna-
- tive algorithm works, this is necessarily the shortest possible match
+ tive algorithm works, this is necessarily the shortest possible match
at the first possible matching point in the subject string.
PCRE_DFA_RESTART
- When pcre_dfa_exec() is called with the PCRE_PARTIAL option, and
- returns a partial match, it is possible to call it again, with addi-
- tional subject characters, and have it continue with the same match.
- The PCRE_DFA_RESTART option requests this action; when it is set, the
- workspace and wscount 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 pcrepartial
+ When pcre_dfa_exec() is called with the PCRE_PARTIAL option, and
+ returns a partial match, it is possible to call it again, with addi-
+ tional subject characters, and have it continue with the same match.
+ The PCRE_DFA_RESTART option requests this action; when it is set, the
+ workspace and wscount 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 pcrepartial
documentation.
Successful returns from pcre_dfa_exec()
- When pcre_dfa_exec() succeeds, it may have matched more than one sub-
+ When pcre_dfa_exec() succeeds, it may have matched more than one sub-
string 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,
+ 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
<.*>
<something> <something else>
<something> <something else> <something further>
- 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 ovector. 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 pcre_exec() returns data, even though the
+ 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 ovector. 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 pcre_exec() returns data, even though the
meaning of the strings is different.)
The strings are returned in reverse order of length; that is, the long-
- est matching string is given first. If there were too many matches to
- fit into ovector, the yield of the function is zero, and the vector is
+ est matching string is given first. If there were too many matches to
+ fit into ovector, the yield of the function is zero, and the vector is
filled with the longest matches.
Error returns from pcre_dfa_exec()
- The pcre_dfa_exec() function returns a negative number when it fails.
- Many of the errors are the same as for pcre_exec(), and these are
- described above. There are in addition the following errors that are
+ The pcre_dfa_exec() function returns a negative number when it fails.
+ Many of the errors are the same as for pcre_exec(), and these are
+ described above. There are in addition the following errors that are
specific to pcre_dfa_exec():
PCRE_ERROR_DFA_UITEM (-16)
- This return is given if pcre_dfa_exec() encounters an item in the pat-
- tern that it does not support, for instance, the use of \C or a back
+ This return is given if pcre_dfa_exec() encounters an item in the pat-
+ tern that it does not support, for instance, the use of \C or a back
reference.
PCRE_ERROR_DFA_UCOND (-17)
- This return is given if pcre_dfa_exec() encounters a condition item
- that uses a back reference for the condition, or a test for recursion
+ This return is given if pcre_dfa_exec() 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.
PCRE_ERROR_DFA_UMLIMIT (-18)
- This return is given if pcre_dfa_exec() is called with an extra block
+ This return is given if pcre_dfa_exec() is called with an extra block
that contains a setting of the match_limit field. This is not supported
(it is meaningless).
PCRE_ERROR_DFA_WSSIZE (-19)
- This return is given if pcre_dfa_exec() runs out of space in the
+ This return is given if pcre_dfa_exec() runs out of space in the
workspace vector.
PCRE_ERROR_DFA_RECURSE (-20)
- When a recursive subpattern is processed, the matching function calls
- itself recursively, using private vectors for ovector and workspace.
- This error is given if the output vector is not large enough. This
+ When a recursive subpattern is processed, the matching function calls
+ itself recursively, using private vectors for ovector and workspace.
+ 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.
SEE ALSO
- pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
- tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
+ pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
+ tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
AUTHOR
REVISION
- Last updated: 21 August 2007
- Copyright (c) 1997-2007 University of Cambridge.
+ Last updated: 23 January 2008
+ Copyright (c) 1997-2008 University of Cambridge.
------------------------------------------------------------------------------
(f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-
TURE options for pcre_exec() have no Perl equivalents.
- (g) The callout facility is PCRE-specific.
+ (g) The \R escape sequence can be restricted to match only CR, LF, or
+ CRLF by the PCRE_BSR_ANYCRLF option.
- (h) The partial matching facility is PCRE-specific.
+ (h) The callout facility is PCRE-specific.
- (i) Patterns compiled by PCRE can be saved and re-used at a later time,
+ (i) The partial matching facility is PCRE-specific.
+
+ (j) Patterns compiled by PCRE can be saved and re-used at a later time,
even on different hosts that have the other endianness.
- (j) The alternative matching function (pcre_dfa_exec()) matches in a
+ (k) The alternative matching function (pcre_dfa_exec()) matches in a
different way and is not Perl-compatible.
+ (l) PCRE recognizes some special sequences such as (*CR) at the start
+ of a pattern that set overall options that cannot be changed within the
+ pattern.
+
AUTHOR
REVISION
- Last updated: 08 August 2007
+ Last updated: 11 September 2007
Copyright (c) 1997-2007 University of Cambridge.
------------------------------------------------------------------------------
changes the convention to CR. That pattern matches "a\nb" because LF is
no longer a newline. Note that these special settings, which are not
Perl-compatible, are recognized only at the very start of a pattern,
- and that they must be in upper case.
+ and that they must be in upper case. If more than one of them is
+ present, the last one is used.
+
+ The newline convention does not affect what the \R escape sequence
+ matches. By default, this is any Unicode newline sequence, for Perl
+ compatibility. However, this can be changed; see the description of \R
+ in the section entitled "Newline sequences" below. A change of \R set-
+ ting can be combined with a change of newline convention.
CHARACTERS AND METACHARACTERS
- A regular expression is a pattern that is matched against a subject
- string from left to right. Most characters stand for themselves in a
- pattern, and match the corresponding characters in the subject. As a
+ A regular expression is a pattern that is matched against a subject
+ string from left to right. Most characters stand for themselves in a
+ pattern, and match the corresponding characters in the subject. As a
trivial example, the pattern
The quick brown fox
matches a portion of a subject string that is identical to itself. When
- caseless matching is specified (the PCRE_CASELESS option), letters are
- matched independently of case. 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 val-
- ues, 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
+ caseless matching is specified (the PCRE_CASELESS option), letters are
+ matched independently of case. 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 val-
+ ues, 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.
- The power of regular expressions comes from the ability to include
- alternatives and repetitions in the pattern. These are encoded in the
+ The power of regular expressions comes from the ability to include
+ alternatives and repetitions in the pattern. These are encoded in the
pattern by the use of metacharacters, which do not stand for themselves
but instead are interpreted in some special way.
- There are two different sets of metacharacters: those that are recog-
- nized anywhere in the pattern except within square brackets, and those
- that are recognized within square brackets. Outside square brackets,
+ There are two different sets of metacharacters: those that are recog-
+ nized anywhere in the pattern except within square brackets, and those
+ that are recognized within square brackets. Outside square brackets,
the metacharacters are as follows:
\ general escape character with several uses
also "possessive quantifier"
{ start min/max quantifier
- Part of a pattern that is in square brackets is called a "character
+ Part of a pattern that is in square brackets is called a "character
class". In a character class the only metacharacters are:
\ general escape character
syntax)
] terminates the character class
- The following sections describe the use of each of the metacharacters.
+ The following sections describe the use of each of the metacharacters.
BACKSLASH
The backslash character has several uses. Firstly, if it is followed by
- a non-alphanumeric character, it takes away any special meaning that
- character may have. This use of backslash as an escape character
+ a non-alphanumeric character, it takes away any special meaning that
+ character may have. This use of backslash as an escape character
applies both inside and outside character classes.
- For example, if you want to match a * character, you write \* in the
- pattern. This escaping action applies whether or not the following
- character would otherwise be interpreted as a metacharacter, so it is
- always safe to precede a non-alphanumeric with backslash to specify
- that it stands for itself. In particular, if you want to match a back-
+ For example, if you want to match a * character, you write \* in the
+ pattern. This escaping action applies whether or not the following
+ character would otherwise be interpreted as a metacharacter, so it is
+ always safe to precede a non-alphanumeric with backslash to specify
+ that it stands for itself. In particular, if you want to match a back-
slash, you write \\.
- If a pattern is compiled with the PCRE_EXTENDED option, whitespace in
- the pattern (other than in a character class) and characters between a
+ If a pattern is compiled with the PCRE_EXTENDED option, whitespace in
+ the pattern (other than in a character class) and characters between a
# outside a character class and the next newline are ignored. An escap-
- ing backslash can be used to include a whitespace or # character as
+ ing backslash can be used to include a whitespace or # character as
part of the pattern.
- If you want to remove the special meaning from a sequence of charac-
- ters, you can do so by putting them between \Q and \E. This is differ-
- ent from Perl in that $ and @ are handled as literals in \Q...\E
- sequences in PCRE, whereas in Perl, $ and @ cause variable interpola-
+ If you want to remove the special meaning from a sequence of charac-
+ ters, you can do so by putting them between \Q and \E. This is differ-
+ ent from Perl in that $ and @ are handled as literals in \Q...\E
+ sequences in PCRE, whereas in Perl, $ and @ cause variable interpola-
tion. Note the following examples:
Pattern PCRE matches Perl matches
\Qabc\$xyz\E abc\$xyz abc\$xyz
\Qabc\E\$\Qxyz\E abc$xyz abc$xyz
- The \Q...\E sequence is recognized both inside and outside character
+ The \Q...\E sequence is recognized both inside and outside character
classes.
Non-printing characters
A second use of backslash provides a way of encoding non-printing char-
- acters in patterns in a visible manner. There is no restriction on the
- appearance of non-printing characters, apart from the binary zero that
- terminates a pattern, but when a pattern is being prepared by text
- editing, it is usually easier to use one of the following escape
+ acters in patterns in a visible manner. There is no restriction on the
+ appearance of non-printing characters, apart from the binary zero that
+ terminates a pattern, but when a pattern is being prepared by text
+ editing, it is usually easier to use one of the following escape
sequences than the binary character it represents:
\a alarm, that is, the BEL character (hex 07)
\xhh character with hex code hh
\x{hhh..} character with hex code hhh..
- The precise effect of \cx is as follows: if x is a lower case letter,
- it is converted to upper case. Then bit 6 of the character (hex 40) is
- inverted. Thus \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;
+ The precise effect of \cx is as follows: if x is a lower case letter,
+ it is converted to upper case. Then bit 6 of the character (hex 40) is
+ inverted. Thus \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;
becomes hex 7B.
- After \x, from zero to two hexadecimal digits are read (letters can be
- in upper or lower case). Any number of hexadecimal digits may appear
- between \x{ and }, but the value of the character code must be less
+ After \x, from zero to two hexadecimal digits are read (letters can be
+ in upper or lower case). Any number of hexadecimal digits may appear
+ between \x{ and }, but the value of the character code must be less
than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
- the maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger
+ the maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger
than the largest Unicode code point, which is 10FFFF.
- If characters other than hexadecimal digits appear between \x{ and },
+ If characters other than hexadecimal digits appear between \x{ and },
or if there is no terminating }, this form of escape is not recognized.
- Instead, the initial \x will be interpreted as a basic hexadecimal
- escape, with no following digits, giving a character whose value is
+ Instead, the initial \x will be interpreted as a basic hexadecimal
+ escape, with no following digits, giving a character whose value is
zero.
Characters whose value is less than 256 can be defined by either of the
- two syntaxes for \x. There is no difference in the way they are han-
+ two syntaxes for \x. There is no difference in the way they are han-
dled. For example, \xdc is exactly the same as \x{dc}.
- After \0 up to two further octal digits are read. If there are fewer
- than two digits, just those that are present are used. Thus the
+ After \0 up to two further octal digits are read. If there are fewer
+ than two digits, just those that are present are used. Thus the
sequence \0\x\07 specifies two binary zeros followed by a BEL character
- (code value 7). Make sure you supply two digits after the initial zero
+ (code value 7). Make sure you supply two digits after the initial zero
if the pattern character that follows is itself an octal digit.
The handling of a backslash followed by a digit other than 0 is compli-
cated. Outside a character class, PCRE reads it and any following dig-
- its as a decimal number. If the number is less than 10, or if there
+ its as a decimal number. If the number is less than 10, or if there
have been at least that many previous capturing left parentheses in the
- expression, the entire sequence is taken as a back reference. A
- description of how this works is given later, following the discussion
+ expression, the entire sequence is taken as a back reference. A
+ description of how this works is given later, following the discussion
of parenthesized subpatterns.
- Inside a character class, or if the decimal number is greater than 9
- and there have not been that many capturing subpatterns, PCRE re-reads
+ Inside a character class, or if the decimal number is greater than 9
+ and there have not been that many capturing subpatterns, PCRE re-reads
up to three octal digits following the backslash, and uses them to gen-
- erate a data character. Any subsequent digits stand for themselves. In
- non-UTF-8 mode, the value of a character specified in octal must be
- less than \400. In UTF-8 mode, values up to \777 are permitted. For
+ erate a data character. Any subsequent digits stand for themselves. In
+ non-UTF-8 mode, the value of a character specified in octal must be
+ less than \400. In UTF-8 mode, values up to \777 are permitted. For
example:
\040 is another way of writing a space
\81 is either a back reference, or a binary zero
followed by the two characters "8" and "1"
- Note that octal values of 100 or greater must not be introduced by a
+ Note that octal values of 100 or greater must not be introduced by a
leading zero, because no more than three octal digits are ever read.
All the sequences that define a single character value can be used both
- inside and outside character classes. In addition, inside a character
- class, the sequence \b is interpreted as the backspace character (hex
- 08), and the sequences \R and \X are interpreted as the characters "R"
- and "X", respectively. Outside a character class, these sequences have
+ inside and outside character classes. In addition, inside a character
+ class, the sequence \b is interpreted as the backspace character (hex
+ 08), and the sequences \R and \X are interpreted as the characters "R"
+ and "X", respectively. Outside a character class, these sequences have
different meanings (see below).
Absolute and relative back references
- The sequence \g followed by an unsigned or a negative number, option-
- ally enclosed in braces, is an absolute or relative back reference. A
+ The sequence \g followed by an unsigned or a negative number, option-
+ ally enclosed in braces, is an absolute or relative back reference. A
named back reference can be coded as \g{name}. Back references are dis-
cussed later, following the discussion of parenthesized subpatterns.
\W any "non-word" character
Each pair of escape sequences partitions the complete set of characters
- into two disjoint sets. Any given character matches one, and only one,
+ into two disjoint sets. Any given character matches one, and only one,
of each pair.
These character type sequences can appear both inside and outside char-
- acter classes. They each match one character of the appropriate type.
- If the current matching point is at the end of the subject string, all
+ acter classes. They each match one character of the appropriate type.
+ If the current matching point is at the end of the subject string, all
of them fail, since there is no character to match.
- For compatibility with Perl, \s does not match the VT character (code
- 11). This makes it different from the the POSIX "space" class. The \s
- characters are HT (9), LF (10), FF (12), CR (13), and space (32). If
+ For compatibility with Perl, \s does not match the VT character (code
+ 11). This makes it different from the the POSIX "space" class. The \s
+ characters are HT (9), LF (10), FF (12), CR (13), and space (32). If
"use locale;" is included in a Perl script, \s may match the VT charac-
ter. In PCRE, it never does.
- In UTF-8 mode, characters with values greater than 128 never match \d,
+ In UTF-8 mode, characters with values greater than 128 never match \d,
\s, or \w, and always match \D, \S, and \W. This is true even when Uni-
- code character property support is available. These sequences retain
+ code character property support is available. These sequences retain
their original meanings from before UTF-8 support was available, mainly
for efficiency reasons.
The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
- the other sequences, these do match certain high-valued codepoints in
+ the other sequences, these do match certain high-valued codepoints in
UTF-8 mode. The horizontal space characters are:
U+0009 Horizontal tab
U+2029 Paragraph separator
A "word" character is an underscore or any character less than 256 that
- is a letter or digit. The definition of letters and digits is con-
- trolled by PCRE's low-valued character tables, and may vary if locale-
- specific matching is taking place (see "Locale support" in the pcreapi
- page). For example, in a French locale such as "fr_FR" in Unix-like
- systems, or "french" in Windows, some character codes greater than 128
- are used for accented letters, and these are matched by \w. The use of
+ is a letter or digit. The definition of letters and digits is con-
+ trolled by PCRE's low-valued character tables, and may vary if locale-
+ specific matching is taking place (see "Locale support" in the pcreapi
+ page). For example, in a French locale such as "fr_FR" in Unix-like
+ systems, or "french" in Windows, some character codes greater than 128
+ are used for accented letters, and these are matched by \w. The use of
locales with Unicode is discouraged.
Newline sequences
- Outside a character class, the escape sequence \R matches any Unicode
- newline sequence. This is a Perl 5.10 feature. In non-UTF-8 mode \R is
- equivalent to the following:
+ Outside a character class, by default, the escape sequence \R matches
+ any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8
+ mode \R is equivalent to the following:
(?>\r\n|\n|\x0b|\f|\r|\x85)
- This is an example of an "atomic group", details of which are given
+ This is an example of an "atomic group", details of which are given
below. This particular group matches either the two-character sequence
- CR followed by LF, or one of the single characters LF (linefeed,
+ CR followed by LF, or one of the single characters LF (linefeed,
U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
return, U+000D), or NEL (next line, U+0085). The two-character sequence
is treated as a single unit that cannot be split.
- In UTF-8 mode, two additional characters whose codepoints are greater
+ In UTF-8 mode, two additional characters whose codepoints are greater
than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
- rator, U+2029). Unicode character property support is not needed for
+ rator, U+2029). Unicode character property support is not needed for
these characters to be recognized.
+ It is possible to restrict \R to match only CR, LF, or CRLF (instead of
+ the complete set of Unicode line endings) by setting the option
+ PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
+ (BSR is an abbrevation for "backslash R".) This can be made the default
+ when PCRE is built; if this is the case, the other behaviour can be
+ requested via the PCRE_BSR_UNICODE option. It is also possible to
+ specify these settings by starting a pattern string with one of the
+ following sequences:
+
+ (*BSR_ANYCRLF) CR, LF, or CRLF only
+ (*BSR_UNICODE) any Unicode newline sequence
+
+ These override the default and the options given to pcre_compile(), but
+ they can be overridden by options given to pcre_exec(). Note that these
+ special settings, which are not Perl-compatible, are recognized only at
+ the very start of a pattern, and that they must be in upper case. If
+ more than one of them is present, the last one is used. They can be
+ combined with a change of newline convention, for example, a pattern
+ can start with:
+
+ (*ANY)(*BSR_ANYCRLF)
+
Inside a character class, \R matches the letter "R".
Unicode character properties
INTERNAL OPTION SETTING
The settings of the PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and
- PCRE_EXTENDED options can be changed from within the pattern by a
- sequence of Perl option letters enclosed between "(?" and ")". The
- option letters are
+ PCRE_EXTENDED options (which are Perl-compatible) can be changed from
+ within the pattern by a sequence of Perl option letters enclosed
+ between "(?" and ")". The option letters are
i for PCRE_CASELESS
m for PCRE_MULTILINE
is also permitted. If a letter appears both before and after the
hyphen, the option is unset.
+ The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA
+ can be changed in the same way as the Perl-compatible options by using
+ the characters J, U and X respectively.
+
When an option change occurs at top level (that is, not inside subpat-
tern parentheses), the change applies to the remainder of the pattern
that follows. If the change is placed right at the start of a pattern,
the effects of option settings happen at compile time. There would be
some very weird behaviour otherwise.
- The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA
- can be changed in the same way as the Perl-compatible options by using
- the characters J, U and X respectively.
+ Note: There are other PCRE-specific options that can be set by the
+ application when the compile or match functions are called. In some
+ cases the pattern can contain special leading sequences to override
+ what the application has set or what has been defaulted. Details are
+ given in the section entitled "Newline sequences" above.
SUBPATTERNS
is given in the pcrecallout documentation.
-BACTRACKING CONTROL
+BACKTRACKING CONTROL
Perl 5.10 introduced a number of "Special Backtracking Control Verbs",
which are described in the Perl documentation as "experimental and sub-
REVISION
- Last updated: 21 August 2007
+ Last updated: 17 September 2007
Copyright (c) 1997-2007 University of Cambridge.
------------------------------------------------------------------------------
[^...] negative character class
[x-y] range (can be used for hex characters)
[[:xxx:]] positive POSIX named set
- [[^:xxx:]] negative POSIX named set
+ [[:^xxx:]] negative POSIX named set
alnum alphanumeric
alpha alphabetic
NEWLINE CONVENTIONS
- These are recognized only at the very start of a pattern.
+ These are recognized only at the very start of the pattern or after a
+ (*BSR_...) option.
(*CR)
(*LF)
(*ANY)
+WHAT \R MATCHES
+
+ These are recognized only at the very start of the pattern or after a
+ (*...) option that sets the newline convention.
+
+ (*BSR_ANYCRLF)
+ (*BSR_UNICODE)
+
+
CALLOUTS
(?C) callout
REVISION
- Last updated: 21 August 2007
+ Last updated: 14 November 2007
Copyright (c) 1997-2007 University of Cambridge.
------------------------------------------------------------------------------
c. The "i"th argument has a suitable type for holding the
string captured as the "i"th sub-pattern. If you pass in
- NULL for the "i"th argument, or pass fewer arguments than
+ void * NULL for the "i"th argument, or a non-void * NULL
+ of the correct type, or pass fewer arguments than the
number of sub-patterns, "i"th captured sub-pattern is
ignored.
REVISION
- Last updated: 06 March 2007
+ Last updated: 12 November 2007
------------------------------------------------------------------------------
bility of matching an empty string. Comments in the code explain what
is going on.
- The demonstration program is automatically built if you use "./config-
- ure;make" to build PCRE. Otherwise, if PCRE is installed in the stan-
- dard include and library directories for your system, you should be
- able to compile the demonstration program using this command:
+ If PCRE is installed in the standard include and library directories
+ for your system, you should be able to compile the demonstration pro-
+ gram using this command:
gcc -o pcredemo pcredemo.c -lpcre
- If PCRE is installed elsewhere, you may need to add additional options
- to the command line. For example, on a Unix-like system that has PCRE
- installed in /usr/local, you can compile the demonstration program
+ If PCRE is installed elsewhere, you may need to add additional options
+ to the command line. For example, on a Unix-like system that has PCRE
+ installed in /usr/local, you can compile the demonstration program
using a command like this:
gcc -o pcredemo -I/usr/local/include pcredemo.c \
-L/usr/local/lib -lpcre
- Once you have compiled the demonstration program, you can run simple
+ Once you have compiled the demonstration program, you can run simple
tests like this:
./pcredemo 'cat|dog' 'the cat sat on the mat'
./pcredemo -g 'cat|dog' 'the dog sat on the cat'
- Note that there is a much more comprehensive test program, called
- pcretest, which supports many more facilities for testing regular
+ Note that there is a much more comprehensive test program, called
+ pcretest, which supports many more facilities for testing regular
expressions and the PCRE library. The pcredemo program is provided as a
simple coding example.
the standard library directory, you may get an error like this when you
try to run pcredemo:
- ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such file or
+ ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such file or
directory
- This is caused by the way shared library support works on those sys-
+ This is caused by the way shared library support works on those sys-
tems. You need to add
-R/usr/local/lib
REVISION
- Last updated: 13 June 2007
- Copyright (c) 1997-2007 University of Cambridge.
+ Last updated: 23 January 2008
+ Copyright (c) 1997-2008 University of Cambridge.
------------------------------------------------------------------------------
PCRESTACK(3) PCRESTACK(3)
projects / php / commitdiff