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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 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 To build PCRE on a Unix-like system, first run the "configure" command from the
72 PCRE distribution directory, with your current directory set to the directory
73 where you want the files to be created. This command is a standard GNU
74 "autoconf" configuration script, for which generic instructions are supplied in
77 Most commonly, people build PCRE within its own distribution directory, and in
78 this case, on many systems, just running "./configure" is sufficient, but the
79 usual methods of changing standard defaults are available. For example:
81 CFLAGS='-O2 -Wall' ./configure --prefix=/opt/local
83 specifies that the C compiler should be run with the flags '-O2 -Wall' instead
84 of the default, and that "make install" should install PCRE under /opt/local
85 instead of the default /usr/local.
87 If you want to build in a different directory, just run "configure" with that
88 directory as current. For example, suppose you have unpacked the PCRE source
89 into /source/pcre/pcre-xxx, but you want to build it in /build/pcre/pcre-xxx:
91 cd /build/pcre/pcre-xxx
92 /source/pcre/pcre-xxx/configure
94 There are some optional features that can be included or omitted from the PCRE
95 library. You can read more about them in the pcrebuild man page.
97 . If you want to make use of the support for UTF-8 character strings in PCRE,
98 you must add --enable-utf8 to the "configure" command. Without it, the code
99 for handling UTF-8 is not included in the library. (Even when included, it
100 still has to be enabled by an option at run time.)
102 . If, in addition to support for UTF-8 character strings, you want to include
103 support for the \P, \p, and \X sequences that recognize Unicode character
104 properties, you must add --enable-unicode-properties to the "configure"
105 command. This adds about 90K to the size of the library (in the form of a
106 property table); only the basic two-letter properties such as Lu are
107 supported.
109 . You can build PCRE to recognized CR or NL as the newline character, instead
110 of whatever your compiler uses for "\n", by adding --newline-is-cr or
111 --newline-is-nl to the "configure" command, respectively. Only do this if you
112 really understand what you are doing. On traditional Unix-like systems, the
113 newline character is NL.
115 . When called via the POSIX interface, PCRE uses malloc() to get additional
116 storage for processing capturing parentheses if there are more than 10 of
117 them. You can increase this threshold by setting, for example,
119 --with-posix-malloc-threshold=20
121 on the "configure" command.
123 . PCRE has a counter that can be set to limit the amount of resources it uses.
124 If the limit is exceeded during a match, the match fails. The default is ten
125 million. You can change the default by setting, for example,
127 --with-match-limit=500000
129 on the "configure" command. This is just the default; individual calls to
130 pcre_exec() can supply their own value. There is discussion on the pcreapi
131 man page.
133 . The default maximum compiled pattern size is around 64K. You can increase
134 this by adding --with-link-size=3 to the "configure" command. You can
135 increase it even more by setting --with-link-size=4, but this is unlikely
136 ever to be necessary. If you build PCRE with an increased link size, test 2
137 (and 5 if you are using UTF-8) will fail. Part of the output of these tests
138 is a representation of the compiled pattern, and this changes with the link
139 size.
141 . You can build PCRE so that its internal match() function that is called from
142 pcre_exec() does not call itself recursively. Instead, it uses blocks of data
143 from the heap via special functions pcre_stack_malloc() and pcre_stack_free()
144 to save data that would otherwise be saved on the stack. To build PCRE like
145 this, use
147 --disable-stack-for-recursion
149 on the "configure" command. PCRE runs more slowly in this mode, but it may be
150 necessary in environments with limited stack sizes. This applies only to the
151 pcre_exec() function; it does not apply to pcre_dfa_exec(), which does not
152 use deeply nested recursion.
154 The "configure" script builds eight files for the basic C library:
156 . pcre.h is the header file for C programs that call PCRE
157 . Makefile is the makefile that builds the library
158 . config.h contains build-time configuration options for the library
159 . pcre-config is a script that shows the settings of "configure" options
160 . libpcre.pc is data for the pkg-config command
161 . libtool is a script that builds shared and/or static libraries
162 . RunTest is a script for running tests on the library
163 . RunGrepTest is a script for running tests on the pcregrep command
165 In addition, if a C++ compiler is found, the following are also built:
167 . pcrecpp.h is the header file for programs that call PCRE via the C++ wrapper
168 . pcre_stringpiece.h is the header for the C++ "stringpiece" functions
170 The "configure" script also creates config.status, which is an executable
171 script that can be run to recreate the configuration, and config.log, which
172 contains compiler output from tests that "configure" runs.
174 Once "configure" has run, you can run "make". It builds two libraries, called
175 libpcre and libpcreposix, a test program called pcretest, and the pcregrep
176 command. If a C++ compiler was found on your system, it also builds the C++
177 wrapper library, which is called libpcrecpp, and some test programs called
178 pcrecpp_unittest, pcre_scanner_unittest, and pcre_stringpiece_unittest.
180 The command "make test" runs all the appropriate tests. Details of the PCRE
181 tests are given in a separate section of this document, below.
183 You can use "make install" to copy the libraries, the public header files
184 pcre.h, pcreposix.h, pcrecpp.h, and pcre_stringpiece.h (the last two only if
185 the C++ wrapper was built), and the man pages to appropriate live directories
186 on your system, in the normal way.
188 If you want to remove PCRE from your system, you can run "make uninstall".
189 This removes all the files that "make install" installed. However, it does not
190 remove any directories, because these are often shared with other programs.
193 Retrieving configuration information on Unix-like systems
194 ---------------------------------------------------------
196 Running "make install" also installs the command pcre-config, which can be used
197 to recall information about the PCRE configuration and installation. For
198 example:
200 pcre-config --version
202 prints the version number, and
204 pcre-config --libs
206 outputs information about where the library is installed. This command can be
207 included in makefiles for programs that use PCRE, saving the programmer from
208 having to remember too many details.
210 The pkg-config command is another system for saving and retrieving information
211 about installed libraries. Instead of separate commands for each library, a
212 single command is used. For example:
214 pkg-config --cflags pcre
216 The data is held in *.pc files that are installed in a directory called
217 pkgconfig.
220 Shared libraries on Unix-like systems
221 -------------------------------------
223 The default distribution builds PCRE as shared libraries and static libraries,
224 as long as the operating system supports shared libraries. Shared library
225 support relies on the "libtool" script which is built as part of the
226 "configure" process.
228 The libtool script is used to compile and link both shared and static
229 libraries. They are placed in a subdirectory called .libs when they are newly
230 built. The programs pcretest and pcregrep are built to use these uninstalled
231 libraries (by means of wrapper scripts in the case of shared libraries). When
232 you use "make install" to install shared libraries, pcregrep and pcretest are
233 automatically re-built to use the newly installed shared libraries before being
234 installed themselves. However, the versions left in the source directory still
235 use the uninstalled libraries.
237 To build PCRE using static libraries only you must use --disable-shared when
238 configuring it. For example:
240 ./configure --prefix=/usr/gnu --disable-shared
242 Then run "make" in the usual way. Similarly, you can use --disable-static to
243 build only shared libraries.
246 Cross-compiling on a Unix-like system
247 -------------------------------------
249 You can specify CC and CFLAGS in the normal way to the "configure" command, in
250 order to cross-compile PCRE for some other host. However, during the building
251 process, the dftables.c source file is compiled *and run* on the local host, in
252 order to generate the default character tables (the chartables.c file). It
253 therefore needs to be compiled with the local compiler, not the cross compiler.
254 You can do this by specifying CC_FOR_BUILD (and if necessary CFLAGS_FOR_BUILD;
255 there are also CXX_FOR_BUILD and CXXFLAGS_FOR_BUILD for the C++ wrapper)
256 when calling the "configure" command. If they are not specified, they default
257 to the values of CC and CFLAGS.
260 Building on non-Unix systems
261 ----------------------------
263 For a non-Unix system, read the comments in the file NON-UNIX-USE, though if
264 the system supports the use of "configure" and "make" you may be able to build
265 PCRE in the same way as for Unix systems.
267 PCRE has been compiled on Windows systems and on Macintoshes, but I don't know
268 the details because I don't use those systems. It should be straightforward to
269 build PCRE on any system that has a Standard C compiler, because it uses only
270 Standard C functions.
273 Testing PCRE
274 ------------
276 To test PCRE on a Unix system, run the RunTest script that is created by the
277 configuring process. There is also a script called RunGrepTest that tests the
278 options of the pcregrep command. If the C++ wrapper library is build, three
279 test programs called pcrecpp_unittest, pcre_scanner_unittest, and
280 pcre_stringpiece_unittest are provided.
282 Both the scripts and all the program tests are run if you obey "make runtest",
283 "make check", or "make test". For other systems, see the instructions in
286 The RunTest script runs the pcretest test program (which is documented in its
287 own man page) on each of the testinput files (in the testdata directory) in
288 turn, and compares the output with the contents of the corresponding testoutput
289 file. A file called testtry is used to hold the main output from pcretest
290 (testsavedregex is also used as a working file). To run pcretest on just one of
291 the test files, give its number as an argument to RunTest, for example:
293 RunTest 2
295 The first file can also be fed directly into the perltest script to check that
296 Perl gives the same results. The only difference you should see is in the first
297 few lines, where the Perl version is given instead of the PCRE version.
299 The second set of tests check pcre_fullinfo(), pcre_info(), pcre_study(),
300 pcre_copy_substring(), pcre_get_substring(), pcre_get_substring_list(), error
301 detection, and run-time flags that are specific to PCRE, as well as the POSIX
302 wrapper API. It also uses the debugging flag to check some of the internals of
303 pcre_compile().
305 If you build PCRE with a locale setting that is not the standard C locale, the
306 character tables may be different (see next paragraph). In some cases, this may
307 cause failures in the second set of tests. For example, in a locale where the
308 isprint() function yields TRUE for characters in the range 128-255, the use of
309 [:isascii:] inside a character class defines a different set of characters, and
310 this shows up in this test as a difference in the compiled code, which is being
311 listed for checking. Where the comparison test output contains [\x00-\x7f] the
312 test will contain [\x00-\xff], and similarly in some other cases. This is not a
313 bug in PCRE.
315 The third set of tests checks pcre_maketables(), the facility for building a
316 set of character tables for a specific locale and using them instead of the
317 default tables. The tests make use of the "fr_FR" (French) locale. Before
318 running the test, the script checks for the presence of this locale by running
319 the "locale" command. If that command fails, or if it doesn't include "fr_FR"
320 in the list of available locales, the third test cannot be run, and a comment
321 is output to say why. If running this test produces instances of the error
323 ** Failed to set locale "fr_FR"
325 in the comparison output, it means that locale is not available on your system,
326 despite being listed by "locale". This does not mean that PCRE is broken.
328 The fourth test checks the UTF-8 support. It is not run automatically unless
329 PCRE is built with UTF-8 support. To do this you must set --enable-utf8 when
330 running "configure". This file can be also fed directly to the perltest script,
331 provided you are running Perl 5.8 or higher. (For Perl 5.6, a small patch,
332 commented in the script, can be be used.)
334 The fifth test checks error handling with UTF-8 encoding, and internal UTF-8
335 features of PCRE that are not relevant to Perl.
337 The sixth and test checks the support for Unicode character properties. It it
338 not run automatically unless PCRE is built with Unicode property support. To to
339 this you must set --enable-unicode-properties when running "configure".
341 The seventh, eighth, and ninth tests check the pcre_dfa_exec() alternative
342 matching function, in non-UTF-8 mode, UTF-8 mode, and UTF-8 mode with Unicode
343 property support, respectively. The eighth and ninth tests are not run
344 automatically unless PCRE is build with the relevant support.
347 Character tables
348 ----------------
350 PCRE uses four tables for manipulating and identifying characters whose values
351 are less than 256. The final argument of the pcre_compile() function is a
352 pointer to a block of memory containing the concatenated tables. A call to
353 pcre_maketables() can be used to generate a set of tables in the current
354 locale. If the final argument for pcre_compile() is passed as NULL, a set of
355 default tables that is built into the binary is used.
357 The source file called chartables.c contains the default set of tables. This is
358 not supplied in the distribution, but is built by the program dftables
359 (compiled from dftables.c), which uses the ANSI C character handling functions
360 such as isalnum(), isalpha(), isupper(), islower(), etc. to build the table
361 sources. This means that the default C locale which is set for your system will
362 control the contents of these default tables. You can change the default tables
363 by editing chartables.c and then re-building PCRE. If you do this, you should
364 probably also edit Makefile to ensure that the file doesn't ever get
365 re-generated.
367 The first two 256-byte tables provide lower casing and case flipping functions,
368 respectively. The next table consists of three 32-byte bit maps which identify
369 digits, "word" characters, and white space, respectively. These are used when
370 building 32-byte bit maps that represent character classes.
372 The final 256-byte table has bits indicating various character types, as
373 follows:
375 1 white space character
376 2 letter
377 4 decimal digit
378 8 hexadecimal digit
379 16 alphanumeric or '_'
380 128 regular expression metacharacter or binary zero
382 You should not alter the set of characters that contain the 128 bit, as that
383 will cause PCRE to malfunction.
386 Manifest
387 --------
389 The distribution should contain the following files:
391 (A) The actual source files of the PCRE library functions and their
392 headers:
394 dftables.c auxiliary program for building chartables.c
396 pcreposix.c )
397 pcre_compile.c )
398 pcre_config.c )
399 pcre_dfa_exec.c )
400 pcre_exec.c )
401 pcre_fullinfo.c )
402 pcre_get.c ) sources for the functions in the library,
403 pcre_globals.c ) and some internal functions that they use
404 pcre_info.c )
405 pcre_maketables.c )
406 pcre_ord2utf8.c )
407 pcre_printint.c )
408 pcre_study.c )
409 pcre_tables.c )
410 pcre_try_flipped.c )
411 pcre_ucp_findchar.c )
412 pcre_valid_utf8.c )
413 pcre_version.c )
414 pcre_xclass.c )
416 ucp_findchar.c )
417 ucp.h ) source for the code that is used for
418 ucpinternal.h ) Unicode property handling
419 ucptable.c )
420 ucptypetable.c )
422 pcre.in "source" for the header for the external API; pcre.h
423 is built from this by "configure"
424 pcreposix.h header for the external POSIX wrapper API
425 pcre_internal.h header for internal use
426 config.in template for config.h, which is built by configure
428 pcrecpp.h.in "source" for the header file for the C++ wrapper
429 pcrecpp.cc )
430 pcre_scanner.cc ) source for the C++ wrapper library
432 pcre_stringpiece.h.in "source" for pcre_stringpiece.h, the header for the
433 C++ stringpiece functions
434 pcre_stringpiece.cc source for the C++ stringpiece functions
436 (B) Auxiliary files:
438 AUTHORS information about the author of PCRE
439 ChangeLog log of changes to the code
440 INSTALL generic installation instructions
441 LICENCE conditions for the use of PCRE
442 COPYING the same, using GNU's standard name
443 Makefile.in template for Unix Makefile, which is built by configure
444 NEWS important changes in this release
445 NON-UNIX-USE notes on building PCRE on non-Unix systems
446 README this file
447 RunTest.in template for a Unix shell script for running tests
448 RunGrepTest.in template for a Unix shell script for pcregrep tests
449 config.guess ) files used by libtool,
450 config.sub ) used only when building a shared library
451 configure a configuring shell script (built by autoconf)
452 configure.in the autoconf input used to build configure
453 doc/Tech.Notes notes on the encoding
454 doc/*.3 man page sources for the PCRE functions
455 doc/*.1 man page sources for pcregrep and pcretest
456 doc/html/* HTML documentation
457 doc/pcre.txt plain text version of the man pages
458 doc/pcretest.txt plain text documentation of test program
459 doc/perltest.txt plain text documentation of Perl test program
460 install-sh a shell script for installing files
461 libpcre.pc.in "source" for libpcre.pc for pkg-config
462 ltmain.sh file used to build a libtool script
463 mkinstalldirs script for making install directories
464 pcretest.c comprehensive test program
465 pcredemo.c simple demonstration of coding calls to PCRE
466 perltest Perl test program
467 pcregrep.c source of a grep utility that uses PCRE
468 pcre-config.in source of script which retains PCRE information
469 pcrecpp_unittest.c )
470 pcre_scanner_unittest.c ) test programs for the C++ wrapper
471 pcre_stringpiece_unittest.c )
472 testdata/testinput* test data for main library tests
473 testdata/testoutput* expected test results
474 testdata/grep* input and output for pcregrep tests
476 (C) Auxiliary files for Win32 DLL
478 libpcre.def
479 libpcreposix.def
480 pcre.def
482 (D) Auxiliary file for VPASCAL
484 makevp.bat
486 Philip Hazel
487 Email local part: ph10
488 Email domain: cam.ac.uk
489 June 2005

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