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1 README file for PCRE (Perl-compatible regular expression library)
2 -----------------------------------------------------------------
4 The latest release of PCRE is always available from
6 ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre-xxx.tar.gz
8 Please read the NEWS file if you are upgrading from a previous release.
11 The PCRE APIs
12 -------------
14 PCRE is written in C, and it has its own API. The distribution now includes a
15 set of C++ wrapper functions, courtesy of Google Inc. (see the pcrecpp man page
16 for details).
18 Also included are a set of C wrapper functions that are based on the POSIX
19 API. These end up in the library called libpcreposix. Note that this just
20 provides a POSIX calling interface to PCRE: the regular expressions themselves
21 still follow Perl syntax and semantics. The header file for the POSIX-style
22 functions is called pcreposix.h. The official POSIX name is regex.h, but I
23 didn't want to risk possible problems with existing files of that name by
24 distributing it that way. To use it with an existing program that uses the
25 POSIX API, it will have to be renamed or pointed at by a link.
27 If you are using the POSIX interface to PCRE and there is already a POSIX regex
28 library installed on your system, you must take care when linking programs to
29 ensure that they link with PCRE's libpcreposix library. Otherwise they may pick
30 up the "real" POSIX functions of the same name.
33 Documentation for PCRE
34 ----------------------
36 If you install PCRE in the normal way, you will end up with an installed set of
37 man pages whose names all start with "pcre". The one that is just called "pcre"
38 lists all the others. In addition to these man pages, the PCRE documentation is
39 supplied in two other forms; however, as there is no standard place to install
40 them, they are left in the doc directory of the unpacked source distribution.
41 These forms are:
43 1. Files called doc/pcre.txt, doc/pcregrep.txt, and doc/pcretest.txt. The
44 first of these is a concatenation of the text forms of all the section 3
45 man pages except those that summarize individual functions. The other two
46 are the text forms of the section 1 man pages for the pcregrep and
47 pcretest commands. Text forms are provided for ease of scanning with text
48 editors or similar tools.
50 2. A subdirectory called doc/html contains all the documentation in HTML
51 form, hyperlinked in various ways, and rooted in a file called
52 doc/index.html.
55 Contributions by users of PCRE
56 ------------------------------
58 You can find contributions from PCRE users in the directory
60 ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/Contrib
62 where there is also a README file giving brief descriptions of what they are.
63 Several of them provide support for compiling PCRE on various flavours of
64 Windows systems (I myself do not use Windows). Some are complete in themselves;
65 others are pointers to URLs containing relevant files.
68 Building PCRE on a Unix-like system
69 -----------------------------------
71 If you are using HP's ANSI C++ compiler (aCC), please see the special note
72 in the section entitled "Using HP's ANSI C++ compiler (aCC)" below.
74 To build PCRE on a Unix-like system, first run the "configure" command from the
75 PCRE distribution directory, with your current directory set to the directory
76 where you want the files to be created. This command is a standard GNU
77 "autoconf" configuration script, for which generic instructions are supplied in
80 Most commonly, people build PCRE within its own distribution directory, and in
81 this case, on many systems, just running "./configure" is sufficient, but the
82 usual methods of changing standard defaults are available. For example:
84 CFLAGS='-O2 -Wall' ./configure --prefix=/opt/local
86 specifies that the C compiler should be run with the flags '-O2 -Wall' instead
87 of the default, and that "make install" should install PCRE under /opt/local
88 instead of the default /usr/local.
90 If you want to build in a different directory, just run "configure" with that
91 directory as current. For example, suppose you have unpacked the PCRE source
92 into /source/pcre/pcre-xxx, but you want to build it in /build/pcre/pcre-xxx:
94 cd /build/pcre/pcre-xxx
95 /source/pcre/pcre-xxx/configure
97 PCRE is written in C and is normally compiled as a C library. However, it is
98 possible to build it as a C++ library, though the provided building apparatus
99 does not have any features to support this.
101 There are some optional features that can be included or omitted from the PCRE
102 library. You can read more about them in the pcrebuild man page.
104 . If you want to suppress the building of the C++ wrapper library, you can add
105 --disable-cpp to the "configure" command. Otherwise, when "configure" is run,
106 will try to find a C++ compiler and C++ header files, and if it succeeds, it
107 will try to build the C++ wrapper.
109 . If you want to make use of the support for UTF-8 character strings in PCRE,
110 you must add --enable-utf8 to the "configure" command. Without it, the code
111 for handling UTF-8 is not included in the library. (Even when included, it
112 still has to be enabled by an option at run time.)
114 . If, in addition to support for UTF-8 character strings, you want to include
115 support for the \P, \p, and \X sequences that recognize Unicode character
116 properties, you must add --enable-unicode-properties to the "configure"
117 command. This adds about 30K to the size of the library (in the form of a
118 property table); only the basic two-letter properties such as Lu are
119 supported.
121 . You can build PCRE to recognize either CR or LF or the sequence CRLF as
122 indicating the end of a line. Whatever you specify at build time is the
123 default; the caller of PCRE can change the selection at run time. The default
124 newline indicator is a single LF character (the Unix standard). You can
125 specify the default newline indicator by adding --newline-is-cr or
126 --newline-is-lf or --newline-is-crlf to the "configure" command,
127 respectively.
129 . When called via the POSIX interface, PCRE uses malloc() to get additional
130 storage for processing capturing parentheses if there are more than 10 of
131 them. You can increase this threshold by setting, for example,
133 --with-posix-malloc-threshold=20
135 on the "configure" command.
137 . PCRE has a counter that can be set to limit the amount of resources it uses.
138 If the limit is exceeded during a match, the match fails. The default is ten
139 million. You can change the default by setting, for example,
141 --with-match-limit=500000
143 on the "configure" command. This is just the default; individual calls to
144 pcre_exec() can supply their own value. There is discussion on the pcreapi
145 man page.
147 . There is a separate counter that limits the depth of recursive function calls
148 during a matching process. This also has a default of ten million, which is
149 essentially "unlimited". You can change the default by setting, for example,
151 --with-match-limit-recursion=500000
153 Recursive function calls use up the runtime stack; running out of stack can
154 cause programs to crash in strange ways. There is a discussion about stack
155 sizes in the pcrestack man page.
157 . The default maximum compiled pattern size is around 64K. You can increase
158 this by adding --with-link-size=3 to the "configure" command. You can
159 increase it even more by setting --with-link-size=4, but this is unlikely
160 ever to be necessary. If you build PCRE with an increased link size, test 2
161 (and 5 if you are using UTF-8) will fail. Part of the output of these tests
162 is a representation of the compiled pattern, and this changes with the link
163 size.
165 . You can build PCRE so that its internal match() function that is called from
166 pcre_exec() does not call itself recursively. Instead, it uses blocks of data
167 from the heap via special functions pcre_stack_malloc() and pcre_stack_free()
168 to save data that would otherwise be saved on the stack. To build PCRE like
169 this, use
171 --disable-stack-for-recursion
173 on the "configure" command. PCRE runs more slowly in this mode, but it may be
174 necessary in environments with limited stack sizes. This applies only to the
175 pcre_exec() function; it does not apply to pcre_dfa_exec(), which does not
176 use deeply nested recursion.
178 The "configure" script builds eight files for the basic C library:
180 . Makefile is the makefile that builds the library
181 . config.h contains build-time configuration options for the library
182 . pcre-config is a script that shows the settings of "configure" options
183 . libpcre.pc is data for the pkg-config command
184 . libtool is a script that builds shared and/or static libraries
185 . RunTest is a script for running tests on the library
186 . RunGrepTest is a script for running tests on the pcregrep command
188 In addition, if a C++ compiler is found, the following are also built:
190 . pcrecpp.h is the header file for programs that call PCRE via the C++ wrapper
191 . pcre_stringpiece.h is the header for the C++ "stringpiece" functions
193 The "configure" script also creates config.status, which is an executable
194 script that can be run to recreate the configuration, and config.log, which
195 contains compiler output from tests that "configure" runs.
197 Once "configure" has run, you can run "make". It builds two libraries, called
198 libpcre and libpcreposix, a test program called pcretest, and the pcregrep
199 command. If a C++ compiler was found on your system, it also builds the C++
200 wrapper library, which is called libpcrecpp, and some test programs called
201 pcrecpp_unittest, pcre_scanner_unittest, and pcre_stringpiece_unittest.
203 The command "make test" runs all the appropriate tests. Details of the PCRE
204 tests are given in a separate section of this document, below.
206 You can use "make install" to copy the libraries, the public header files
207 pcre.h, pcreposix.h, pcrecpp.h, and pcre_stringpiece.h (the last two only if
208 the C++ wrapper was built), and the man pages to appropriate live directories
209 on your system, in the normal way.
211 If you want to remove PCRE from your system, you can run "make uninstall".
212 This removes all the files that "make install" installed. However, it does not
213 remove any directories, because these are often shared with other programs.
216 Retrieving configuration information on Unix-like systems
217 ---------------------------------------------------------
219 Running "make install" also installs the command pcre-config, which can be used
220 to recall information about the PCRE configuration and installation. For
221 example:
223 pcre-config --version
225 prints the version number, and
227 pcre-config --libs
229 outputs information about where the library is installed. This command can be
230 included in makefiles for programs that use PCRE, saving the programmer from
231 having to remember too many details.
233 The pkg-config command is another system for saving and retrieving information
234 about installed libraries. Instead of separate commands for each library, a
235 single command is used. For example:
237 pkg-config --cflags pcre
239 The data is held in *.pc files that are installed in a directory called
240 pkgconfig.
243 Shared libraries on Unix-like systems
244 -------------------------------------
246 The default distribution builds PCRE as shared libraries and static libraries,
247 as long as the operating system supports shared libraries. Shared library
248 support relies on the "libtool" script which is built as part of the
249 "configure" process.
251 The libtool script is used to compile and link both shared and static
252 libraries. They are placed in a subdirectory called .libs when they are newly
253 built. The programs pcretest and pcregrep are built to use these uninstalled
254 libraries (by means of wrapper scripts in the case of shared libraries). When
255 you use "make install" to install shared libraries, pcregrep and pcretest are
256 automatically re-built to use the newly installed shared libraries before being
257 installed themselves. However, the versions left in the source directory still
258 use the uninstalled libraries.
260 To build PCRE using static libraries only you must use --disable-shared when
261 configuring it. For example:
263 ./configure --prefix=/usr/gnu --disable-shared
265 Then run "make" in the usual way. Similarly, you can use --disable-static to
266 build only shared libraries.
269 Cross-compiling on a Unix-like system
270 -------------------------------------
272 You can specify CC and CFLAGS in the normal way to the "configure" command, in
273 order to cross-compile PCRE for some other host. However, during the building
274 process, the dftables.c source file is compiled *and run* on the local host, in
275 order to generate the default character tables (the chartables.c file). It
276 therefore needs to be compiled with the local compiler, not the cross compiler.
277 You can do this by specifying CC_FOR_BUILD (and if necessary CFLAGS_FOR_BUILD;
278 there are also CXX_FOR_BUILD and CXXFLAGS_FOR_BUILD for the C++ wrapper)
279 when calling the "configure" command. If they are not specified, they default
280 to the values of CC and CFLAGS.
283 Using HP's ANSI C++ compiler (aCC)
284 ----------------------------------
286 Unless C++ support is disabled by specifiying the "--disable-cpp" option of the
287 "configure" script, you *must* include the "-AA" option in the CXXFLAGS
288 environment variable in order for the C++ components to compile correctly.
290 Also, note that the aCC compiler on PA-RISC platforms may have a defect whereby
291 needed libraries fail to get included when specifying the "-AA" compiler
292 option. If you experience unresolved symbols when linking the C++ programs,
293 use the workaround of specifying the following environment variable prior to
294 running the "configure" script:
296 CXXLDFLAGS="-lstd_v2 -lCsup_v2"
299 Building on non-Unix systems
300 ----------------------------
302 For a non-Unix system, read the comments in the file NON-UNIX-USE, though if
303 the system supports the use of "configure" and "make" you may be able to build
304 PCRE in the same way as for Unix systems.
306 PCRE has been compiled on Windows systems and on Macintoshes, but I don't know
307 the details because I don't use those systems. It should be straightforward to
308 build PCRE on any system that has a Standard C compiler, because it uses only
309 Standard C functions.
312 Testing PCRE
313 ------------
315 To test PCRE on a Unix system, run the RunTest script that is created by the
316 configuring process. There is also a script called RunGrepTest that tests the
317 options of the pcregrep command. If the C++ wrapper library is build, three
318 test programs called pcrecpp_unittest, pcre_scanner_unittest, and
319 pcre_stringpiece_unittest are provided.
321 Both the scripts and all the program tests are run if you obey "make runtest",
322 "make check", or "make test". For other systems, see the instructions in
325 The RunTest script runs the pcretest test program (which is documented in its
326 own man page) on each of the testinput files (in the testdata directory) in
327 turn, and compares the output with the contents of the corresponding testoutput
328 file. A file called testtry is used to hold the main output from pcretest
329 (testsavedregex is also used as a working file). To run pcretest on just one of
330 the test files, give its number as an argument to RunTest, for example:
332 RunTest 2
334 The first file can also be fed directly into the perltest script to check that
335 Perl gives the same results. The only difference you should see is in the first
336 few lines, where the Perl version is given instead of the PCRE version.
338 The second set of tests check pcre_fullinfo(), pcre_info(), pcre_study(),
339 pcre_copy_substring(), pcre_get_substring(), pcre_get_substring_list(), error
340 detection, and run-time flags that are specific to PCRE, as well as the POSIX
341 wrapper API. It also uses the debugging flag to check some of the internals of
342 pcre_compile().
344 If you build PCRE with a locale setting that is not the standard C locale, the
345 character tables may be different (see next paragraph). In some cases, this may
346 cause failures in the second set of tests. For example, in a locale where the
347 isprint() function yields TRUE for characters in the range 128-255, the use of
348 [:isascii:] inside a character class defines a different set of characters, and
349 this shows up in this test as a difference in the compiled code, which is being
350 listed for checking. Where the comparison test output contains [\x00-\x7f] the
351 test will contain [\x00-\xff], and similarly in some other cases. This is not a
352 bug in PCRE.
354 The third set of tests checks pcre_maketables(), the facility for building a
355 set of character tables for a specific locale and using them instead of the
356 default tables. The tests make use of the "fr_FR" (French) locale. Before
357 running the test, the script checks for the presence of this locale by running
358 the "locale" command. If that command fails, or if it doesn't include "fr_FR"
359 in the list of available locales, the third test cannot be run, and a comment
360 is output to say why. If running this test produces instances of the error
362 ** Failed to set locale "fr_FR"
364 in the comparison output, it means that locale is not available on your system,
365 despite being listed by "locale". This does not mean that PCRE is broken.
367 The fourth test checks the UTF-8 support. It is not run automatically unless
368 PCRE is built with UTF-8 support. To do this you must set --enable-utf8 when
369 running "configure". This file can be also fed directly to the perltest script,
370 provided you are running Perl 5.8 or higher. (For Perl 5.6, a small patch,
371 commented in the script, can be be used.)
373 The fifth test checks error handling with UTF-8 encoding, and internal UTF-8
374 features of PCRE that are not relevant to Perl.
376 The sixth and test checks the support for Unicode character properties. It it
377 not run automatically unless PCRE is built with Unicode property support. To to
378 this you must set --enable-unicode-properties when running "configure".
380 The seventh, eighth, and ninth tests check the pcre_dfa_exec() alternative
381 matching function, in non-UTF-8 mode, UTF-8 mode, and UTF-8 mode with Unicode
382 property support, respectively. The eighth and ninth tests are not run
383 automatically unless PCRE is build with the relevant support.
386 Character tables
387 ----------------
389 PCRE uses four tables for manipulating and identifying characters whose values
390 are less than 256. The final argument of the pcre_compile() function is a
391 pointer to a block of memory containing the concatenated tables. A call to
392 pcre_maketables() can be used to generate a set of tables in the current
393 locale. If the final argument for pcre_compile() is passed as NULL, a set of
394 default tables that is built into the binary is used.
396 The source file called chartables.c contains the default set of tables. This is
397 not supplied in the distribution, but is built by the program dftables
398 (compiled from dftables.c), which uses the ANSI C character handling functions
399 such as isalnum(), isalpha(), isupper(), islower(), etc. to build the table
400 sources. This means that the default C locale which is set for your system will
401 control the contents of these default tables. You can change the default tables
402 by editing chartables.c and then re-building PCRE. If you do this, you should
403 probably also edit Makefile to ensure that the file doesn't ever get
404 re-generated.
406 The first two 256-byte tables provide lower casing and case flipping functions,
407 respectively. The next table consists of three 32-byte bit maps which identify
408 digits, "word" characters, and white space, respectively. These are used when
409 building 32-byte bit maps that represent character classes.
411 The final 256-byte table has bits indicating various character types, as
412 follows:
414 1 white space character
415 2 letter
416 4 decimal digit
417 8 hexadecimal digit
418 16 alphanumeric or '_'
419 128 regular expression metacharacter or binary zero
421 You should not alter the set of characters that contain the 128 bit, as that
422 will cause PCRE to malfunction.
425 Manifest
426 --------
428 The distribution should contain the following files:
430 (A) The actual source files of the PCRE library functions and their
431 headers:
433 dftables.c auxiliary program for building chartables.c
435 pcreposix.c )
436 pcre_compile.c )
437 pcre_config.c )
438 pcre_dfa_exec.c )
439 pcre_exec.c )
440 pcre_fullinfo.c )
441 pcre_get.c ) sources for the functions in the library,
442 pcre_globals.c ) and some internal functions that they use
443 pcre_info.c )
444 pcre_maketables.c )
445 pcre_ord2utf8.c )
446 pcre_refcount.c )
447 pcre_study.c )
448 pcre_tables.c )
449 pcre_try_flipped.c )
450 pcre_ucp_searchfuncs.c)
451 pcre_valid_utf8.c )
452 pcre_version.c )
453 pcre_xclass.c )
454 ucptable.c )
456 pcre_printint.src ) debugging function that is #included in pcretest, and
457 ) can also be #included in pcre_compile()
459 pcre.h the public PCRE header file
460 pcreposix.h header for the external POSIX wrapper API
461 pcre_internal.h header for internal use
462 ucp.h ) headers concerned with
463 ucpinternal.h ) Unicode property handling
464 config.in template for config.h, which is built by configure
466 pcrecpp.h the header file for the C++ wrapper
467 pcrecpparg.h.in "source" for another C++ header file
468 pcrecpp.cc )
469 pcre_scanner.cc ) source for the C++ wrapper library
471 pcre_stringpiece.h.in "source" for pcre_stringpiece.h, the header for the
472 C++ stringpiece functions
473 pcre_stringpiece.cc source for the C++ stringpiece functions
475 (B) Auxiliary files:
477 AUTHORS information about the author of PCRE
478 ChangeLog log of changes to the code
479 INSTALL generic installation instructions
480 LICENCE conditions for the use of PCRE
481 COPYING the same, using GNU's standard name
482 Makefile.in template for Unix Makefile, which is built by configure
483 NEWS important changes in this release
484 NON-UNIX-USE notes on building PCRE on non-Unix systems
485 README this file
486 RunTest.in template for a Unix shell script for running tests
487 RunGrepTest.in template for a Unix shell script for pcregrep tests
488 config.guess ) files used by libtool,
489 config.sub ) used only when building a shared library
490 config.h.in "source" for the config.h header file
491 configure a configuring shell script (built by autoconf)
492 configure.ac the autoconf input used to build configure
493 doc/Tech.Notes notes on the encoding
494 doc/*.3 man page sources for the PCRE functions
495 doc/*.1 man page sources for pcregrep and pcretest
496 doc/html/* HTML documentation
497 doc/pcre.txt plain text version of the man pages
498 doc/pcretest.txt plain text documentation of test program
499 doc/perltest.txt plain text documentation of Perl test program
500 install-sh a shell script for installing files
501 libpcre.pc.in "source" for libpcre.pc for pkg-config
502 ltmain.sh file used to build a libtool script
503 mkinstalldirs script for making install directories
504 pcretest.c comprehensive test program
505 pcredemo.c simple demonstration of coding calls to PCRE
506 perltest Perl test program
507 pcregrep.c source of a grep utility that uses PCRE
508 pcre-config.in source of script which retains PCRE information
509 pcrecpp_unittest.c )
510 pcre_scanner_unittest.c ) test programs for the C++ wrapper
511 pcre_stringpiece_unittest.c )
512 testdata/testinput* test data for main library tests
513 testdata/testoutput* expected test results
514 testdata/grep* input and output for pcregrep tests
516 (C) Auxiliary files for Win32 DLL
518 libpcre.def
519 libpcreposix.def
521 (D) Auxiliary file for VPASCAL
523 makevp.bat
525 Philip Hazel
526 Email local part: ph10
527 Email domain: cam.ac.uk
528 June 2006

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