PCREBUILD(3)               Library Functions Manual               PCREBUILD(3)

       PCRE - Perl-compatible regular expressions


       PCRE  is  distributed with a configure script that can be used to build
       the library in Unix-like environments using the applications  known  as
       Autotools.   Also in the distribution are files to support building us-
       ing CMake instead of configure. The text file README  contains  general
       information  about  building  with Autotools (some of which is repeated
       below), and also has some comments about building on various  operating
       systems.  There  is  a lot more information about building PCRE without
       using Autotools (including information about using CMake  and  building
       "by  hand")  in  the  text file called NON-AUTOTOOLS-BUILD.  You should
       consult this file as well as the README file if you are building  in  a
       non-Unix-like environment.


       The  rest of this document describes the optional features of PCRE that
       can be selected when the library is compiled. It  assumes  use  of  the
       configure  script,  where  the  optional features are selected or dese-
       lected by providing options to configure before running the  make  com-
       mand.  However,  the same options can be selected in both Unix-like and
       non-Unix-like environments using the GUI facility of cmake-gui  if  you
       are using CMake instead of configure to build PCRE.

       If  you  are not using Autotools or CMake, option selection can be done
       by editing the config.h file, or by passing parameter settings  to  the
       compiler, as described in NON-AUTOTOOLS-BUILD.

       The complete list of options for configure (which includes the standard
       ones such as the selection of the installation directory)  can  be  ob-
       tained by running

         ./configure --help

       The  following sections include descriptions of options whose names be-
       gin 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
       is not described.


       By default, a library called libpcre  is  built,  containing  functions
       that  take  string  arguments  contained in vectors of bytes, either as
       single-byte characters, or interpreted as UTF-8 strings. You  can  also
       build  a  separate library, called libpcre16, in which strings are con-
       tained in vectors of 16-bit data units and interpreted either  as  sin-
       gle-unit characters or UTF-16 strings, by adding


       to  the  configure command. You can also build yet another separate li-
       brary, called libpcre32, in which strings are contained in  vectors  of
       32-bit  data  units and interpreted either as single-unit characters or
       UTF-32 strings, by adding


       to the configure command. If you do not want the 8-bit library, add


       as well. At least one of the three libraries must be built.  Note  that
       the  C++  and  POSIX  wrappers are for the 8-bit library only, and that
       pcregrep is an 8-bit program. None of these are  built  if  you  select
       only the 16-bit or 32-bit libraries.


       The  Autotools  PCRE building process uses libtool to build both shared
       and static libraries by default. You  can  suppress  one  of  these  by
       adding one of


       to the configure command, as required.


       By  default,  if the 8-bit library is being built, the configure script
       will search for a C++ compiler and C++ header files. If it finds  them,
       it  automatically  builds  the C++ wrapper library (which supports only
       8-bit strings). You can disable this by adding


       to the configure command.


       To build PCRE with support for UTF Unicode character strings, add


       to the configure command. This setting applies to all three  libraries,
       adding  support  for  UTF-8 to the 8-bit library, support for UTF-16 to
       the 16-bit library, and support for UTF-32 to the  to  the  32-bit  li-
       brary.  There  are  no  separate options for enabling UTF-8, UTF-16 and
       UTF-32 independently because that would allow ridiculous settings  such
       as  requesting UTF-16 support while building only the 8-bit library. It
       is not possible to build one library with UTF support and another with-
       out  in the same configuration. (For backwards compatibility, --enable-
       utf8 is a synonym of --enable-utf.)

       Of itself, this setting does not make  PCRE  treat  strings  as  UTF-8,
       UTF-16  or UTF-32. As well as compiling PCRE with this option, you also
       have have to set the PCRE_UTF8, PCRE_UTF16 or PCRE_UTF32 option (as ap-
       propriate) when you call one of the pattern compiling functions.

       If  you  set --enable-utf when compiling in an EBCDIC environment, PCRE
       expects its input to be either ASCII or UTF-8 (depending  on  the  run-
       time option). It is not possible to support both EBCDIC and UTF-8 codes
       in the same version of  the  library.  Consequently,  --enable-utf  and
       --enable-ebcdic are mutually exclusive.


       UTF  support allows the libraries to process character codepoints up to
       0x10ffff in the strings that they handle. On its own, however, it  does
       not provide any facilities for accessing the properties of such charac-
       ters. If you want to be able to use the pattern escapes \P, \p, and \X,
       which refer to Unicode character properties, you must add


       to  the  configure  command. This implies UTF 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
       are supported. Details are given in the pcrepattern documentation.


       Just-in-time compiler support is included in the build by specifying


       This support is available only for certain hardware  architectures.  If
       this  option is set for an unsupported architecture, a compile time er-
       ror occurs.  See the pcrejit documentation for a discussion of JIT  us-
       age.  When  JIT support is enabled, pcregrep automatically makes use of
       it, unless you add


       to the "configure" command.


       By default, PCRE interprets the linefeed (LF) character  as  indicating
       the  end  of  a line. This is the normal newline character on Unix-like
       systems. You can compile PCRE to use carriage return (CR)  instead,  by


       to  the  configure  command. There is also a --enable-newline-is-lf op-
       tion, which explicitly specifies linefeed as the newline character.

       Alternatively, you can specify that line endings are to be indicated by
       the two character sequence CRLF. If you want this, add


       to the configure command. There is a fourth option, specified by


       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


       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
       conventional to use the standard for your operating system.


       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


       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.


       When the 8-bit library is called through the POSIX interface  (see  the
       pcreposix  documentation),  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  func-
       tion  uses  space  on the stack, because this is faster than using mal-
       loc() for each call. The default threshold above which the stack is  no
       longer used is 10; it can be changed by adding a setting such as


       to the configure command.


       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, in the 8-bit and 16-bit libraries,
       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  truly  enormous patterns, so it is possible to compile PCRE to
       use three-byte or four-byte offsets by adding a setting such as


       to the configure command. The value given must be 2, 3, or 4.  For  the
       16-bit  library,  a  value of 3 is rounded up to 4. In these libraries,
       using longer offsets slows down the operation of PCRE because it has to
       load  additional  data  when  handling them. For the 32-bit library the
       value is always 4 and cannot be overridden; the value  of  --with-link-
       size is ignored.


       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
       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.
       If you want to build a version of PCRE that works this way, add


       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 instead.

       Separate  functions  are  provided  rather  than  using pcre_malloc and
       pcre_free because the usage is very predictable: the  block  sizes  re-
       quested 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 pcre_dfa_exec().


       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


       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
       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-
       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 im-
       poses no additional constraints. However, you can set a lower limit  by
       adding, for example,


       to  the  configure  command.  This  value can also be overridden at run


       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


       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 run-time 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
       have to do so "by hand".)


       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


       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 en-
       vironment (for example, an IBM mainframe operating system).  The  --en-
       able-ebcdic option is incompatible with --enable-utf.

       The EBCDIC character that corresponds to an ASCII LF is assumed to have
       the value 0x15 by default. However, in some EBCDIC  environments,  0x25
       is used. In such an environment you should use


       as well as, or instead of, --enable-ebcdic. The EBCDIC character for CR
       has the same value as in ASCII, namely, 0x0d.  Whichever  of  0x15  and
       0x25 is not chosen as LF is made to correspond to the Unicode NEL char-
       acter (which, in Unicode, is 0x85).

       The options that select newline behaviour, such as --enable-newline-is-
       cr, and equivalent run-time options, refer to these character values in
       an EBCDIC environment.


       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


       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.


       pcregrep uses an internal buffer to hold a "window" on the file  it  is
       scanning, in order to be able to output "before" and "after" lines when
       it finds a match. The size of the buffer is controlled by  a  parameter
       whose default value is 20K. The buffer itself is three times this size,
       but because of the way it is used for holding "before" lines, the long-
       est  line  that  is guaranteed to be processable is the parameter size.
       You can change the default parameter value by adding, for example,


       to the configure command. The caller of pcregrep can, however, override
       this value by specifying a run-time option.


       If you add


       to  the  configure command, pcretest is linked with the libreadline li-
       brary, 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-licensed, so if you distribute a binary of
       pcretest linked in this way, there may be licensing issues.

       Setting  this  option  causes  the -lreadline option to be added to the
       pcretest build. In many operating environments with  a  sytem-installed
       libreadline this is sufficient. However, in some environments (e.g.  if
       an unmodified distribution version of readline is in use),  some  extra
       configuration  may  be necessary. The INSTALL file for libreadline says

         "Readline uses the termcap functions, but does not link with the
         termcap or curses library itself, allowing applications which link
         with readline the to choose an appropriate library."

       If your environment has not been set up so that an appropriate  library
       is automatically included, you may need to add something like


       immediately before the configure command.


       By adding the


       option  to to the configure command, PCRE will use valgrind annotations
       to mark certain memory regions as unaddressable. This allows it to  de-
       tect  invalid  memory accesses, and is mostly useful for debugging PCRE


       If your C compiler is gcc, you can build a version  of  PCRE  that  can
       generate a code coverage report for its test suite. To enable this, you
       must install lcov version 1.6 or above. Then specify


       to the configure command and build PCRE in the usual way.

       Note that using ccache (a caching C compiler) is incompatible with code
       coverage  reporting. If you have configured ccache to run automatically
       on your system, you must set the environment variable


       before running make to build PCRE, so that ccache is not used.

       When --enable-coverage is used,  the  following  addition  targets  are
       added to the Makefile:

         make coverage

       This  creates  a  fresh  coverage report for the PCRE test suite. It is
       equivalent to running "make coverage-reset", "make  coverage-baseline",
       "make check", and then "make coverage-report".

         make coverage-reset

       This zeroes the coverage counters, but does nothing else.

         make coverage-baseline

       This captures baseline coverage information.

         make coverage-report

       This creates the coverage report.

         make coverage-clean-report

       This  removes the generated coverage report without cleaning the cover-
       age data itself.

         make coverage-clean-data

       This removes the captured coverage data without removing  the  coverage
       files created at compile time (*.gcno).

         make coverage-clean

       This  cleans all coverage data including the generated coverage report.
       For more information about code coverage, see the gcov and  lcov  docu-


       pcreapi(3), pcre16, pcre32, pcre_config(3).


       Philip Hazel
       University Computing Service
       Cambridge CB2 3QH, England.


       Last updated: 12 May 2013
       Copyright (c) 1997-2013 University of Cambridge.

PCRE 8.33                         12 May 2013                     PCREBUILD(3)
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