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README file for PCRE (Perl-compatible regular expression library) ----------------------------------------------------------------- The latest release of PCRE is always available from ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre-xxx.tar.gz Please read the NEWS file if you are upgrading from a previous release. The PCRE APIs ------------- PCRE is written in C, and it has its own API. The distribution now includes a set of C++ wrapper functions, courtesy of Google Inc. (see the pcrecpp man page for details). Also included are a set of C wrapper functions that are based on the POSIX API. These end up in the library called libpcreposix. Note that this just provides a POSIX calling interface to PCRE: the regular expressions themselves still follow Perl syntax and semantics. The header file for the POSIX-style functions is called pcreposix.h. The official POSIX name is regex.h, but I didn't want to risk possible problems with existing files of that name by distributing it that way. To use it with an existing program that uses the POSIX API, it will have to be renamed or pointed at by a link. If you are using the POSIX interface to PCRE and there is already a POSIX regex library installed on your system, you must take care when linking programs to ensure that they link with PCRE's libpcreposix library. Otherwise they may pick up the "real" POSIX functions of the same name. Documentation for PCRE ---------------------- If you install PCRE in the normal way, you will end up with an installed set of man pages whose names all start with "pcre". The one that is just called "pcre" lists all the others. In addition to these man pages, the PCRE documentation is supplied in two other forms; however, as there is no standard place to install them, they are left in the doc directory of the unpacked source distribution. These forms are: 1. Files called doc/pcre.txt, doc/pcregrep.txt, and doc/pcretest.txt. The first of these is a concatenation of the text forms of all the section 3 man pages except those that summarize individual functions. The other two are the text forms of the section 1 man pages for the pcregrep and pcretest commands. Text forms are provided for ease of scanning with text editors or similar tools. 2. A subdirectory called doc/html contains all the documentation in HTML form, hyperlinked in various ways, and rooted in a file called doc/index.html. Contributions by users of PCRE ------------------------------ You can find contributions from PCRE users in the directory ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/Contrib where there is also a README file giving brief descriptions of what they are. Several of them provide support for compiling PCRE on various flavours of Windows systems (I myself do not use Windows). Some are complete in themselves; others are pointers to URLs containing relevant files. Building PCRE on a Unix-like system ----------------------------------- If you are using HP's ANSI C++ compiler (aCC), please see the special note in the section entitled "Using HP's ANSI C++ compiler (aCC)" below. To build PCRE on a Unix-like system, first run the "configure" command from the PCRE distribution directory, with your current directory set to the directory where you want the files to be created. This command is a standard GNU "autoconf" configuration script, for which generic instructions are supplied in INSTALL. Most commonly, people build PCRE within its own distribution directory, and in this case, on many systems, just running "./configure" is sufficient, but the usual methods of changing standard defaults are available. For example: CFLAGS='-O2 -Wall' ./configure --prefix=/opt/local specifies that the C compiler should be run with the flags '-O2 -Wall' instead of the default, and that "make install" should install PCRE under /opt/local instead of the default /usr/local. If you want to build in a different directory, just run "configure" with that directory as current. For example, suppose you have unpacked the PCRE source into /source/pcre/pcre-xxx, but you want to build it in /build/pcre/pcre-xxx: cd /build/pcre/pcre-xxx /source/pcre/pcre-xxx/configure PCRE is written in C and is normally compiled as a C library. However, it is possible to build it as a C++ library, though the provided building apparatus does not have any features to support this. There are some optional features that can be included or omitted from the PCRE library. You can read more about them in the pcrebuild man page. . If you want to suppress the building of the C++ wrapper library, you can add --disable-cpp to the "configure" command. Otherwise, when "configure" is run, will try to find a C++ compiler and C++ header files, and if it succeeds, it will try to build the C++ wrapper. . If you want to make use of the support for UTF-8 character strings in PCRE, you must add --enable-utf8 to the "configure" command. Without it, the code for handling UTF-8 is not included in the library. (Even when included, it still has to be enabled by an option at run time.) . If, in addition to support for UTF-8 character strings, you want to include support for the \P, \p, and \X sequences that recognize Unicode character properties, you must add --enable-unicode-properties to the "configure" command. This adds about 30K to the size of the library (in the form of a property table); only the basic two-letter properties such as Lu are supported. . You can build PCRE to recognize either CR or LF or the sequence CRLF or any of the Unicode newline sequences as indicating the end of a line. Whatever you specify at build time is the default; the caller of PCRE can change the selection at run time. The default newline indicator is a single LF character (the Unix standard). You can specify the default newline indicator by adding --newline-is-cr or --newline-is-lf or --newline-is-crlf or --newline-is-any to the "configure" command, respectively. . When called via the POSIX interface, PCRE uses malloc() to get additional storage for processing capturing parentheses if there are more than 10 of them. You can increase this threshold by setting, for example, --with-posix-malloc-threshold=20 on the "configure" command. . PCRE has a counter that can be set to limit the amount of resources it uses. If the limit is exceeded during a match, the match fails. The default is ten million. You can change the default by setting, for example, --with-match-limit=500000 on the "configure" command. This is just the default; individual calls to pcre_exec() can supply their own value. There is discussion on the pcreapi man page. . There is a separate counter that limits the depth of recursive function calls during a matching process. This also has a default of ten million, which is essentially "unlimited". You can change the default by setting, for example, --with-match-limit-recursion=500000 Recursive function calls use up the runtime stack; running out of stack can cause programs to crash in strange ways. There is a discussion about stack sizes in the pcrestack man page. . The default maximum compiled pattern size is around 64K. You can increase this by adding --with-link-size=3 to the "configure" command. You can increase it even more by setting --with-link-size=4, but this is unlikely ever to be necessary. If you build PCRE with an increased link size, test 2 (and 5 if you are using UTF-8) will fail. Part of the output of these tests is a representation of the compiled pattern, and this changes with the link size. . You can build PCRE so that its internal match() function that is called from pcre_exec() does not call itself recursively. Instead, it uses blocks of data from the heap via special functions pcre_stack_malloc() and pcre_stack_free() to save data that would otherwise be saved on the stack. To build PCRE like this, use --disable-stack-for-recursion on the "configure" command. PCRE runs more slowly in this mode, but it may be necessary in environments with limited stack sizes. This applies only to the pcre_exec() function; it does not apply to pcre_dfa_exec(), which does not use deeply nested recursion. The "configure" script builds eight files for the basic C library: . Makefile is the makefile that builds the library . config.h contains build-time configuration options for the library . pcre-config is a script that shows the settings of "configure" options . libpcre.pc is data for the pkg-config command . libtool is a script that builds shared and/or static libraries . RunTest is a script for running tests on the library . RunGrepTest is a script for running tests on the pcregrep command In addition, if a C++ compiler is found, the following are also built: . pcrecpp.h is the header file for programs that call PCRE via the C++ wrapper . pcre_stringpiece.h is the header for the C++ "stringpiece" functions The "configure" script also creates config.status, which is an executable script that can be run to recreate the configuration, and config.log, which contains compiler output from tests that "configure" runs. Once "configure" has run, you can run "make". It builds two libraries, called libpcre and libpcreposix, a test program called pcretest, and the pcregrep command. If a C++ compiler was found on your system, it also builds the C++ wrapper library, which is called libpcrecpp, and some test programs called pcrecpp_unittest, pcre_scanner_unittest, and pcre_stringpiece_unittest. The command "make test" runs all the appropriate tests. Details of the PCRE tests are given in a separate section of this document, below. You can use "make install" to copy the libraries, the public header files pcre.h, pcreposix.h, pcrecpp.h, and pcre_stringpiece.h (the last two only if the C++ wrapper was built), and the man pages to appropriate live directories on your system, in the normal way. If you want to remove PCRE from your system, you can run "make uninstall". This removes all the files that "make install" installed. However, it does not remove any directories, because these are often shared with other programs. Retrieving configuration information on Unix-like systems --------------------------------------------------------- Running "make install" also installs the command pcre-config, which can be used to recall information about the PCRE configuration and installation. For example: pcre-config --version prints the version number, and pcre-config --libs outputs information about where the library is installed. This command can be included in makefiles for programs that use PCRE, saving the programmer from having to remember too many details. The pkg-config command is another system for saving and retrieving information about installed libraries. Instead of separate commands for each library, a single command is used. For example: pkg-config --cflags pcre The data is held in *.pc files that are installed in a directory called pkgconfig. Shared libraries on Unix-like systems ------------------------------------- The default distribution builds PCRE as shared libraries and static libraries, as long as the operating system supports shared libraries. Shared library support relies on the "libtool" script which is built as part of the "configure" process. The libtool script is used to compile and link both shared and static libraries. They are placed in a subdirectory called .libs when they are newly built. The programs pcretest and pcregrep are built to use these uninstalled libraries (by means of wrapper scripts in the case of shared libraries). When you use "make install" to install shared libraries, pcregrep and pcretest are automatically re-built to use the newly installed shared libraries before being installed themselves. However, the versions left in the source directory still use the uninstalled libraries. To build PCRE using static libraries only you must use --disable-shared when configuring it. For example: ./configure --prefix=/usr/gnu --disable-shared Then run "make" in the usual way. Similarly, you can use --disable-static to build only shared libraries. Cross-compiling on a Unix-like system ------------------------------------- You can specify CC and CFLAGS in the normal way to the "configure" command, in order to cross-compile PCRE for some other host. However, during the building process, the dftables.c source file is compiled *and run* on the local host, in order to generate the default character tables (the chartables.c file). It therefore needs to be compiled with the local compiler, not the cross compiler. You can do this by specifying CC_FOR_BUILD (and if necessary CFLAGS_FOR_BUILD; there are also CXX_FOR_BUILD and CXXFLAGS_FOR_BUILD for the C++ wrapper) when calling the "configure" command. If they are not specified, they default to the values of CC and CFLAGS. Using HP's ANSI C++ compiler (aCC) ---------------------------------- Unless C++ support is disabled by specifying the "--disable-cpp" option of the "configure" script, you *must* include the "-AA" option in the CXXFLAGS environment variable in order for the C++ components to compile correctly. Also, note that the aCC compiler on PA-RISC platforms may have a defect whereby needed libraries fail to get included when specifying the "-AA" compiler option. If you experience unresolved symbols when linking the C++ programs, use the workaround of specifying the following environment variable prior to running the "configure" script: CXXLDFLAGS="-lstd_v2 -lCsup_v2" Building on non-Unix systems ---------------------------- For a non-Unix system, read the comments in the file NON-UNIX-USE, though if the system supports the use of "configure" and "make" you may be able to build PCRE in the same way as for Unix systems. PCRE has been compiled on Windows systems and on Macintoshes, but I don't know the details because I don't use those systems. It should be straightforward to build PCRE on any system that has a Standard C compiler and library, because it uses only Standard C functions. Testing PCRE ------------ To test PCRE on a Unix system, run the RunTest script that is created by the configuring process. There is also a script called RunGrepTest that tests the options of the pcregrep command. If the C++ wrapper library is build, three test programs called pcrecpp_unittest, pcre_scanner_unittest, and pcre_stringpiece_unittest are provided. Both the scripts and all the program tests are run if you obey "make runtest", "make check", or "make test". For other systems, see the instructions in NON-UNIX-USE. The RunTest script runs the pcretest test program (which is documented in its own man page) on each of the testinput files (in the testdata directory) in turn, and compares the output with the contents of the corresponding testoutput files. A file called testtry is used to hold the main output from pcretest (testsavedregex is also used as a working file). To run pcretest on just one of the test files, give its number as an argument to RunTest, for example: RunTest 2 The first test file can also be fed directly into the perltest script to check that Perl gives the same results. The only difference you should see is in the first few lines, where the Perl version is given instead of the PCRE version. The second set of tests check pcre_fullinfo(), pcre_info(), pcre_study(), pcre_copy_substring(), pcre_get_substring(), pcre_get_substring_list(), error detection, and run-time flags that are specific to PCRE, as well as the POSIX wrapper API. It also uses the debugging flag to check some of the internals of pcre_compile(). If you build PCRE with a locale setting that is not the standard C locale, the character tables may be different (see next paragraph). In some cases, this may cause failures in the second set of tests. For example, in a locale where the isprint() function yields TRUE for characters in the range 128-255, the use of [:isascii:] inside a character class defines a different set of characters, and this shows up in this test as a difference in the compiled code, which is being listed for checking. Where the comparison test output contains [\x00-\x7f] the test will contain [\x00-\xff], and similarly in some other cases. This is not a bug in PCRE. The third set of tests checks pcre_maketables(), the facility for building a set of character tables for a specific locale and using them instead of the default tables. The tests make use of the "fr_FR" (French) locale. Before running the test, the script checks for the presence of this locale by running the "locale" command. If that command fails, or if it doesn't include "fr_FR" in the list of available locales, the third test cannot be run, and a comment is output to say why. If running this test produces instances of the error ** Failed to set locale "fr_FR" in the comparison output, it means that locale is not available on your system, despite being listed by "locale". This does not mean that PCRE is broken. The fourth test checks the UTF-8 support. It is not run automatically unless PCRE is built with UTF-8 support. To do this you must set --enable-utf8 when running "configure". This file can be also fed directly to the perltest script, provided you are running Perl 5.8 or higher. (For Perl 5.6, a small patch, commented in the script, can be be used.) The fifth test checks error handling with UTF-8 encoding, and internal UTF-8 features of PCRE that are not relevant to Perl. The sixth and test checks the support for Unicode character properties. It it not run automatically unless PCRE is built with Unicode property support. To to this you must set --enable-unicode-properties when running "configure". The seventh, eighth, and ninth tests check the pcre_dfa_exec() alternative matching function, in non-UTF-8 mode, UTF-8 mode, and UTF-8 mode with Unicode property support, respectively. The eighth and ninth tests are not run automatically unless PCRE is build with the relevant support. Character tables ---------------- PCRE uses four tables for manipulating and identifying characters whose values are less than 256. The final argument of the pcre_compile() function is a pointer to a block of memory containing the concatenated tables. A call to pcre_maketables() can be used to generate a set of tables in the current locale. If the final argument for pcre_compile() is passed as NULL, a set of default tables that is built into the binary is used. The source file called chartables.c contains the default set of tables. This is not supplied in the distribution, but is built by the program dftables (compiled from dftables.c), which uses the ANSI C character handling functions such as isalnum(), isalpha(), isupper(), islower(), etc. to build the table sources. This means that the default C locale which is set for your system will control the contents of these default tables. You can change the default tables by editing chartables.c and then re-building PCRE. If you do this, you should probably also edit Makefile to ensure that the file doesn't ever get re-generated. The first two 256-byte tables provide lower casing and case flipping functions, respectively. The next table consists of three 32-byte bit maps which identify digits, "word" characters, and white space, respectively. These are used when building 32-byte bit maps that represent character classes. The final 256-byte table has bits indicating various character types, as follows: 1 white space character 2 letter 4 decimal digit 8 hexadecimal digit 16 alphanumeric or '_' 128 regular expression metacharacter or binary zero You should not alter the set of characters that contain the 128 bit, as that will cause PCRE to malfunction. Manifest -------- The distribution should contain the following files: (A) The actual source files of the PCRE library functions and their headers: dftables.c auxiliary program for building chartables.c pcreposix.c ) pcre_compile.c ) pcre_config.c ) pcre_dfa_exec.c ) pcre_exec.c ) pcre_fullinfo.c ) pcre_get.c ) sources for the functions in the library, pcre_globals.c ) and some internal functions that they use pcre_info.c ) pcre_maketables.c ) pcre_newline.c ) pcre_ord2utf8.c ) pcre_refcount.c ) pcre_study.c ) pcre_tables.c ) pcre_try_flipped.c ) pcre_ucp_searchfuncs.c) pcre_valid_utf8.c ) pcre_version.c ) pcre_xclass.c ) ucptable.c ) pcre_printint.src ) debugging function that is #included in pcretest, and ) can also be #included in pcre_compile() pcre.h the public PCRE header file pcreposix.h header for the external POSIX wrapper API pcre_internal.h header for internal use ucp.h ) headers concerned with ucpinternal.h ) Unicode property handling config.in template for config.h, which is built by configure pcrecpp.h the header file for the C++ wrapper pcrecpparg.h.in "source" for another C++ header file pcrecpp.cc ) pcre_scanner.cc ) source for the C++ wrapper library pcre_stringpiece.h.in "source" for pcre_stringpiece.h, the header for the C++ stringpiece functions pcre_stringpiece.cc source for the C++ stringpiece functions (B) Auxiliary files: AUTHORS information about the author of PCRE ChangeLog log of changes to the code INSTALL generic installation instructions LICENCE conditions for the use of PCRE COPYING the same, using GNU's standard name Makefile.in template for Unix Makefile, which is built by configure NEWS important changes in this release NON-UNIX-USE notes on building PCRE on non-Unix systems README this file RunTest.in template for a Unix shell script for running tests RunGrepTest.in template for a Unix shell script for pcregrep tests config.guess ) files used by libtool, config.sub ) used only when building a shared library config.h.in "source" for the config.h header file configure a configuring shell script (built by autoconf) configure.ac the autoconf input used to build configure doc/Tech.Notes notes on the encoding doc/*.3 man page sources for the PCRE functions doc/*.1 man page sources for pcregrep and pcretest doc/html/* HTML documentation doc/pcre.txt plain text version of the man pages doc/pcretest.txt plain text documentation of test program doc/perltest.txt plain text documentation of Perl test program install-sh a shell script for installing files libpcre.pc.in "source" for libpcre.pc for pkg-config ltmain.sh file used to build a libtool script mkinstalldirs script for making install directories pcretest.c comprehensive test program pcredemo.c simple demonstration of coding calls to PCRE perltest Perl test program pcregrep.c source of a grep utility that uses PCRE pcre-config.in source of script which retains PCRE information pcrecpp_unittest.c ) pcre_scanner_unittest.c ) test programs for the C++ wrapper pcre_stringpiece_unittest.c ) testdata/testinput* test data for main library tests testdata/testoutput* expected test results testdata/grep* input and output for pcregrep tests (C) Auxiliary files for Win32 DLL libpcre.def libpcreposix.def (D) Auxiliary file for VPASCAL makevp.bat Philip Hazel Email local part: ph10 Email domain: cam.ac.uk November 2006