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1 README file for PCRE (Perl-compatible regular expression library)
2 -----------------------------------------------------------------
3
4 The latest release of PCRE is always available from
5
6 ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre-xxx.tar.gz
7
8 Please read the NEWS file if you are upgrading from a previous release.
9
10
11 The PCRE APIs
12 -------------
13
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).
17
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.
26
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.
31
32
33 Documentation for PCRE
34 ----------------------
35
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:
42
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.
49
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.
53
54
55 Contributions by users of PCRE
56 ------------------------------
57
58 You can find contributions from PCRE users in the directory
59
60 ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/Contrib
61
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.
66
67
68 Building PCRE on a Unix-like system
69 -----------------------------------
70
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.
73
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
78 INSTALL.
79
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:
83
84 CFLAGS='-O2 -Wall' ./configure --prefix=/opt/local
85
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.
89
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:
93
94 cd /build/pcre/pcre-xxx
95 /source/pcre/pcre-xxx/configure
96
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.
100
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.
103
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.
108
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.)
113
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 90K 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.
120
121 . You can build PCRE to recognize either CR or LF as the newline character,
122 instead of whatever your compiler uses for "\n", by adding --newline-is-cr or
123 --newline-is-lf to the "configure" command, respectively. Only do this if you
124 really understand what you are doing. On traditional Unix-like systems, the
125 newline character is LF.
126
127 . When called via the POSIX interface, PCRE uses malloc() to get additional
128 storage for processing capturing parentheses if there are more than 10 of
129 them. You can increase this threshold by setting, for example,
130
131 --with-posix-malloc-threshold=20
132
133 on the "configure" command.
134
135 . PCRE has a counter that can be set to limit the amount of resources it uses.
136 If the limit is exceeded during a match, the match fails. The default is ten
137 million. You can change the default by setting, for example,
138
139 --with-match-limit=500000
140
141 on the "configure" command. This is just the default; individual calls to
142 pcre_exec() can supply their own value. There is discussion on the pcreapi
143 man page.
144
145 . The default maximum compiled pattern size is around 64K. You can increase
146 this by adding --with-link-size=3 to the "configure" command. You can
147 increase it even more by setting --with-link-size=4, but this is unlikely
148 ever to be necessary. If you build PCRE with an increased link size, test 2
149 (and 5 if you are using UTF-8) will fail. Part of the output of these tests
150 is a representation of the compiled pattern, and this changes with the link
151 size.
152
153 . You can build PCRE so that its internal match() function that is called from
154 pcre_exec() does not call itself recursively. Instead, it uses blocks of data
155 from the heap via special functions pcre_stack_malloc() and pcre_stack_free()
156 to save data that would otherwise be saved on the stack. To build PCRE like
157 this, use
158
159 --disable-stack-for-recursion
160
161 on the "configure" command. PCRE runs more slowly in this mode, but it may be
162 necessary in environments with limited stack sizes. This applies only to the
163 pcre_exec() function; it does not apply to pcre_dfa_exec(), which does not
164 use deeply nested recursion.
165
166 The "configure" script builds eight files for the basic C library:
167
168 . pcre.h is the header file for C programs that call PCRE
169 . Makefile is the makefile that builds the library
170 . config.h contains build-time configuration options for the library
171 . pcre-config is a script that shows the settings of "configure" options
172 . libpcre.pc is data for the pkg-config command
173 . libtool is a script that builds shared and/or static libraries
174 . RunTest is a script for running tests on the library
175 . RunGrepTest is a script for running tests on the pcregrep command
176
177 In addition, if a C++ compiler is found, the following are also built:
178
179 . pcrecpp.h is the header file for programs that call PCRE via the C++ wrapper
180 . pcre_stringpiece.h is the header for the C++ "stringpiece" functions
181
182 The "configure" script also creates config.status, which is an executable
183 script that can be run to recreate the configuration, and config.log, which
184 contains compiler output from tests that "configure" runs.
185
186 Once "configure" has run, you can run "make". It builds two libraries, called
187 libpcre and libpcreposix, a test program called pcretest, and the pcregrep
188 command. If a C++ compiler was found on your system, it also builds the C++
189 wrapper library, which is called libpcrecpp, and some test programs called
190 pcrecpp_unittest, pcre_scanner_unittest, and pcre_stringpiece_unittest.
191
192 The command "make test" runs all the appropriate tests. Details of the PCRE
193 tests are given in a separate section of this document, below.
194
195 You can use "make install" to copy the libraries, the public header files
196 pcre.h, pcreposix.h, pcrecpp.h, and pcre_stringpiece.h (the last two only if
197 the C++ wrapper was built), and the man pages to appropriate live directories
198 on your system, in the normal way.
199
200 If you want to remove PCRE from your system, you can run "make uninstall".
201 This removes all the files that "make install" installed. However, it does not
202 remove any directories, because these are often shared with other programs.
203
204
205 Retrieving configuration information on Unix-like systems
206 ---------------------------------------------------------
207
208 Running "make install" also installs the command pcre-config, which can be used
209 to recall information about the PCRE configuration and installation. For
210 example:
211
212 pcre-config --version
213
214 prints the version number, and
215
216 pcre-config --libs
217
218 outputs information about where the library is installed. This command can be
219 included in makefiles for programs that use PCRE, saving the programmer from
220 having to remember too many details.
221
222 The pkg-config command is another system for saving and retrieving information
223 about installed libraries. Instead of separate commands for each library, a
224 single command is used. For example:
225
226 pkg-config --cflags pcre
227
228 The data is held in *.pc files that are installed in a directory called
229 pkgconfig.
230
231
232 Shared libraries on Unix-like systems
233 -------------------------------------
234
235 The default distribution builds PCRE as shared libraries and static libraries,
236 as long as the operating system supports shared libraries. Shared library
237 support relies on the "libtool" script which is built as part of the
238 "configure" process.
239
240 The libtool script is used to compile and link both shared and static
241 libraries. They are placed in a subdirectory called .libs when they are newly
242 built. The programs pcretest and pcregrep are built to use these uninstalled
243 libraries (by means of wrapper scripts in the case of shared libraries). When
244 you use "make install" to install shared libraries, pcregrep and pcretest are
245 automatically re-built to use the newly installed shared libraries before being
246 installed themselves. However, the versions left in the source directory still
247 use the uninstalled libraries.
248
249 To build PCRE using static libraries only you must use --disable-shared when
250 configuring it. For example:
251
252 ./configure --prefix=/usr/gnu --disable-shared
253
254 Then run "make" in the usual way. Similarly, you can use --disable-static to
255 build only shared libraries.
256
257
258 Cross-compiling on a Unix-like system
259 -------------------------------------
260
261 You can specify CC and CFLAGS in the normal way to the "configure" command, in
262 order to cross-compile PCRE for some other host. However, during the building
263 process, the dftables.c source file is compiled *and run* on the local host, in
264 order to generate the default character tables (the chartables.c file). It
265 therefore needs to be compiled with the local compiler, not the cross compiler.
266 You can do this by specifying CC_FOR_BUILD (and if necessary CFLAGS_FOR_BUILD;
267 there are also CXX_FOR_BUILD and CXXFLAGS_FOR_BUILD for the C++ wrapper)
268 when calling the "configure" command. If they are not specified, they default
269 to the values of CC and CFLAGS.
270
271
272 Using HP's ANSI C++ compiler (aCC)
273 ----------------------------------
274
275 Unless C++ support is disabled by specifiying the "--disable-cpp" option of the
276 "configure" script, you *must* include the "-AA" option in the CXXFLAGS
277 environment variable in order for the C++ components to compile correctly.
278
279 Also, note that the aCC compiler on PA-RISC platforms may have a defect whereby
280 needed libraries fail to get included when specifying the "-AA" compiler
281 option. If you experience unresolved symbols when linking the C++ programs,
282 use the workaround of specifying the following environment variable prior to
283 running the "configure" script:
284
285 CXXLDFLAGS="-lstd_v2 -lCsup_v2"
286
287
288 Building on non-Unix systems
289 ----------------------------
290
291 For a non-Unix system, read the comments in the file NON-UNIX-USE, though if
292 the system supports the use of "configure" and "make" you may be able to build
293 PCRE in the same way as for Unix systems.
294
295 PCRE has been compiled on Windows systems and on Macintoshes, but I don't know
296 the details because I don't use those systems. It should be straightforward to
297 build PCRE on any system that has a Standard C compiler, because it uses only
298 Standard C functions.
299
300
301 Testing PCRE
302 ------------
303
304 To test PCRE on a Unix system, run the RunTest script that is created by the
305 configuring process. There is also a script called RunGrepTest that tests the
306 options of the pcregrep command. If the C++ wrapper library is build, three
307 test programs called pcrecpp_unittest, pcre_scanner_unittest, and
308 pcre_stringpiece_unittest are provided.
309
310 Both the scripts and all the program tests are run if you obey "make runtest",
311 "make check", or "make test". For other systems, see the instructions in
312 NON-UNIX-USE.
313
314 The RunTest script runs the pcretest test program (which is documented in its
315 own man page) on each of the testinput files (in the testdata directory) in
316 turn, and compares the output with the contents of the corresponding testoutput
317 file. A file called testtry is used to hold the main output from pcretest
318 (testsavedregex is also used as a working file). To run pcretest on just one of
319 the test files, give its number as an argument to RunTest, for example:
320
321 RunTest 2
322
323 The first file can also be fed directly into the perltest script to check that
324 Perl gives the same results. The only difference you should see is in the first
325 few lines, where the Perl version is given instead of the PCRE version.
326
327 The second set of tests check pcre_fullinfo(), pcre_info(), pcre_study(),
328 pcre_copy_substring(), pcre_get_substring(), pcre_get_substring_list(), error
329 detection, and run-time flags that are specific to PCRE, as well as the POSIX
330 wrapper API. It also uses the debugging flag to check some of the internals of
331 pcre_compile().
332
333 If you build PCRE with a locale setting that is not the standard C locale, the
334 character tables may be different (see next paragraph). In some cases, this may
335 cause failures in the second set of tests. For example, in a locale where the
336 isprint() function yields TRUE for characters in the range 128-255, the use of
337 [:isascii:] inside a character class defines a different set of characters, and
338 this shows up in this test as a difference in the compiled code, which is being
339 listed for checking. Where the comparison test output contains [\x00-\x7f] the
340 test will contain [\x00-\xff], and similarly in some other cases. This is not a
341 bug in PCRE.
342
343 The third set of tests checks pcre_maketables(), the facility for building a
344 set of character tables for a specific locale and using them instead of the
345 default tables. The tests make use of the "fr_FR" (French) locale. Before
346 running the test, the script checks for the presence of this locale by running
347 the "locale" command. If that command fails, or if it doesn't include "fr_FR"
348 in the list of available locales, the third test cannot be run, and a comment
349 is output to say why. If running this test produces instances of the error
350
351 ** Failed to set locale "fr_FR"
352
353 in the comparison output, it means that locale is not available on your system,
354 despite being listed by "locale". This does not mean that PCRE is broken.
355
356 The fourth test checks the UTF-8 support. It is not run automatically unless
357 PCRE is built with UTF-8 support. To do this you must set --enable-utf8 when
358 running "configure". This file can be also fed directly to the perltest script,
359 provided you are running Perl 5.8 or higher. (For Perl 5.6, a small patch,
360 commented in the script, can be be used.)
361
362 The fifth test checks error handling with UTF-8 encoding, and internal UTF-8
363 features of PCRE that are not relevant to Perl.
364
365 The sixth and test checks the support for Unicode character properties. It it
366 not run automatically unless PCRE is built with Unicode property support. To to
367 this you must set --enable-unicode-properties when running "configure".
368
369 The seventh, eighth, and ninth tests check the pcre_dfa_exec() alternative
370 matching function, in non-UTF-8 mode, UTF-8 mode, and UTF-8 mode with Unicode
371 property support, respectively. The eighth and ninth tests are not run
372 automatically unless PCRE is build with the relevant support.
373
374
375 Character tables
376 ----------------
377
378 PCRE uses four tables for manipulating and identifying characters whose values
379 are less than 256. The final argument of the pcre_compile() function is a
380 pointer to a block of memory containing the concatenated tables. A call to
381 pcre_maketables() can be used to generate a set of tables in the current
382 locale. If the final argument for pcre_compile() is passed as NULL, a set of
383 default tables that is built into the binary is used.
384
385 The source file called chartables.c contains the default set of tables. This is
386 not supplied in the distribution, but is built by the program dftables
387 (compiled from dftables.c), which uses the ANSI C character handling functions
388 such as isalnum(), isalpha(), isupper(), islower(), etc. to build the table
389 sources. This means that the default C locale which is set for your system will
390 control the contents of these default tables. You can change the default tables
391 by editing chartables.c and then re-building PCRE. If you do this, you should
392 probably also edit Makefile to ensure that the file doesn't ever get
393 re-generated.
394
395 The first two 256-byte tables provide lower casing and case flipping functions,
396 respectively. The next table consists of three 32-byte bit maps which identify
397 digits, "word" characters, and white space, respectively. These are used when
398 building 32-byte bit maps that represent character classes.
399
400 The final 256-byte table has bits indicating various character types, as
401 follows:
402
403 1 white space character
404 2 letter
405 4 decimal digit
406 8 hexadecimal digit
407 16 alphanumeric or '_'
408 128 regular expression metacharacter or binary zero
409
410 You should not alter the set of characters that contain the 128 bit, as that
411 will cause PCRE to malfunction.
412
413
414 Manifest
415 --------
416
417 The distribution should contain the following files:
418
419 (A) The actual source files of the PCRE library functions and their
420 headers:
421
422 dftables.c auxiliary program for building chartables.c
423
424 pcreposix.c )
425 pcre_compile.c )
426 pcre_config.c )
427 pcre_dfa_exec.c )
428 pcre_exec.c )
429 pcre_fullinfo.c )
430 pcre_get.c ) sources for the functions in the library,
431 pcre_globals.c ) and some internal functions that they use
432 pcre_info.c )
433 pcre_maketables.c )
434 pcre_ord2utf8.c )
435 pcre_printint.c )
436 pcre_study.c )
437 pcre_tables.c )
438 pcre_try_flipped.c )
439 pcre_ucp_findchar.c )
440 pcre_valid_utf8.c )
441 pcre_version.c )
442 pcre_xclass.c )
443
444 ucp_findchar.c )
445 ucp.h ) source for the code that is used for
446 ucpinternal.h ) Unicode property handling
447 ucptable.c )
448 ucptypetable.c )
449
450 pcre.in "source" for the header for the external API; pcre.h
451 is built from this by "configure"
452 pcreposix.h header for the external POSIX wrapper API
453 pcre_internal.h header for internal use
454 config.in template for config.h, which is built by configure
455
456 pcrecpp.h the header file for the C++ wrapper
457 pcrecpparg.h.in "source" for another C++ header file
458 pcrecpp.cc )
459 pcre_scanner.cc ) source for the C++ wrapper library
460
461 pcre_stringpiece.h.in "source" for pcre_stringpiece.h, the header for the
462 C++ stringpiece functions
463 pcre_stringpiece.cc source for the C++ stringpiece functions
464
465 (B) Auxiliary files:
466
467 AUTHORS information about the author of PCRE
468 ChangeLog log of changes to the code
469 INSTALL generic installation instructions
470 LICENCE conditions for the use of PCRE
471 COPYING the same, using GNU's standard name
472 Makefile.in template for Unix Makefile, which is built by configure
473 NEWS important changes in this release
474 NON-UNIX-USE notes on building PCRE on non-Unix systems
475 README this file
476 RunTest.in template for a Unix shell script for running tests
477 RunGrepTest.in template for a Unix shell script for pcregrep tests
478 config.guess ) files used by libtool,
479 config.sub ) used only when building a shared library
480 configure a configuring shell script (built by autoconf)
481 configure.in the autoconf input used to build configure
482 doc/Tech.Notes notes on the encoding
483 doc/*.3 man page sources for the PCRE functions
484 doc/*.1 man page sources for pcregrep and pcretest
485 doc/html/* HTML documentation
486 doc/pcre.txt plain text version of the man pages
487 doc/pcretest.txt plain text documentation of test program
488 doc/perltest.txt plain text documentation of Perl test program
489 install-sh a shell script for installing files
490 libpcre.pc.in "source" for libpcre.pc for pkg-config
491 ltmain.sh file used to build a libtool script
492 mkinstalldirs script for making install directories
493 pcretest.c comprehensive test program
494 pcredemo.c simple demonstration of coding calls to PCRE
495 perltest Perl test program
496 pcregrep.c source of a grep utility that uses PCRE
497 pcre-config.in source of script which retains PCRE information
498 pcrecpp_unittest.c )
499 pcre_scanner_unittest.c ) test programs for the C++ wrapper
500 pcre_stringpiece_unittest.c )
501 testdata/testinput* test data for main library tests
502 testdata/testoutput* expected test results
503 testdata/grep* input and output for pcregrep tests
504
505 (C) Auxiliary files for Win32 DLL
506
507 libpcre.def
508 libpcreposix.def
509 pcre.def
510
511 (D) Auxiliary file for VPASCAL
512
513 makevp.bat
514
515 Philip Hazel
516 Email local part: ph10
517 Email domain: cam.ac.uk
518 January 2006

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