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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.
10 PCRE has its own native API, but a set of "wrapper" functions that are based on
11 the POSIX API are also supplied in the library libpcreposix. Note that this
12 just provides a POSIX calling interface to PCRE: the regular expressions
13 themselves still follow Perl syntax and semantics. The header file
14 for the POSIX-style functions is called pcreposix.h. The official POSIX name is
15 regex.h, but I didn't want to risk possible problems with existing files of
16 that name by distributing it that way. To use it with an existing program that
17 uses the POSIX API, it will have to be renamed or pointed at by a link.
20 Contributions by users of PCRE
21 ------------------------------
23 You can find contributions from PCRE users in the directory
25 ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/Contrib
27 where there is also a README file giving brief descriptions of what they are.
28 Several of them provide support for compiling PCRE on various flavours of
29 Windows systems (I myself do not use Windows). Some are complete in themselves;
30 others are pointers to URLs containing relevant files.
33 Building PCRE on a Unix-like system
34 -----------------------------------
36 To build PCRE on a Unix-like system, first run the "configure" command from the
37 PCRE distribution directory, with your current directory set to the directory
38 where you want the files to be created. This command is a standard GNU
39 "autoconf" configuration script, for which generic instructions are supplied in
42 Most commonly, people build PCRE within its own distribution directory, and in
43 this case, on many systems, just running "./configure" is sufficient, but the
44 usual methods of changing standard defaults are available. For example,
46 CFLAGS='-O2 -Wall' ./configure --prefix=/opt/local
48 specifies that the C compiler should be run with the flags '-O2 -Wall' instead
49 of the default, and that "make install" should install PCRE under /opt/local
50 instead of the default /usr/local.
52 If you want to build in a different directory, just run "configure" with that
53 directory as current. For example, suppose you have unpacked the PCRE source
54 into /source/pcre/pcre-xxx, but you want to build it in /build/pcre/pcre-xxx:
56 cd /build/pcre/pcre-xxx
57 /source/pcre/pcre-xxx/configure
59 There are some optional features that can be included or omitted from the PCRE
60 library. You can read more about them in the pcrebuild man page.
62 . If you want to make use of the support for UTF-8 character strings in PCRE,
63 you must add --enable-utf8 to the "configure" command. Without it, the code
64 for handling UTF-8 is not included in the library. (Even when included, it
65 still has to be enabled by an option at run time.)
67 . You can build PCRE to recognized CR or NL as the newline character, instead
68 of whatever your compiler uses for "\n", by adding --newline-is-cr or
69 --newline-is-nl to the "configure" command, respectively. Only do this if you
70 really understand what you are doing. On traditional Unix-like systems, the
71 newline character is NL.
73 . When called via the POSIX interface, PCRE uses malloc() to get additional
74 storage for processing capturing parentheses if there are more than 10 of
75 them. You can increase this threshold by setting, for example,
77 --with-posix-malloc-threshold=20
79 on the "configure" command.
81 . PCRE has a counter which can be set to limit the amount of resources it uses.
82 If the limit is exceeded during a match, the match fails. The default is ten
83 million. You can change the default by setting, for example,
85 --with-match-limit=500000
87 on the "configure" command. This is just the default; individual calls to
88 pcre_exec() can supply their own value. There is discussion on the pcreapi
89 man page.
91 . The default maximum compiled pattern size is around 64K. You can increase
92 this by adding --with-link-size=3 to the "configure" command. You can
93 increase it even more by setting --with-link-size=4, but this is unlikely
94 ever to be necessary. If you build PCRE with an increased link size, test 2
95 (and 5 if you are using UTF-8) will fail. Part of the output of these tests
96 is a representation of the compiled pattern, and this changes with the link
97 size.
99 The "configure" script builds five files:
101 . libtool is a script that builds shared and/or static libraries
102 . Makefile is built by copying Makefile.in and making substitutions.
103 . config.h is built by copying config.in and making substitutions.
104 . pcre-config is built by copying pcre-config.in and making substitutions.
105 . RunTest is a script for running tests
107 Once "configure" has run, you can run "make". It builds two libraries called
108 libpcre and libpcreposix, a test program called pcretest, and the pcregrep
109 command. You can use "make install" to copy these, the public header files
110 pcre.h and pcreposix.h, and the man pages to appropriate live directories on
111 your system, in the normal way.
113 Running "make install" also installs the command pcre-config, which can be used
114 to recall information about the PCRE configuration and installation. For
115 example,
117 pcre-config --version
119 prints the version number, and
121 pcre-config --libs
123 outputs information about where the library is installed. This command can be
124 included in makefiles for programs that use PCRE, saving the programmer from
125 having to remember too many details.
128 Cross-compiling PCRE on a Unix-like system
129 ------------------------------------------
131 PCRE needs to compile and run an auxiliary program as part of the building
132 process. Obviously, if the real compilation is for some other system, it can't
133 use the same CC and CFLAGS values when it is doing this. For cross compilation,
134 therefore, you must set CC_FOR_BUILD to the local host's compiler, and you can
135 set flags in CFLAGS_FOR_BUILD if you need to.
138 Shared libraries on Unix-like systems
139 -------------------------------------
141 The default distribution builds PCRE as two shared libraries and two static
142 libraries, as long as the operating system supports shared libraries. Shared
143 library support relies on the "libtool" script which is built as part of the
144 "configure" process.
146 The libtool script is used to compile and link both shared and static
147 libraries. They are placed in a subdirectory called .libs when they are newly
148 built. The programs pcretest and pcregrep are built to use these uninstalled
149 libraries (by means of wrapper scripts in the case of shared libraries). When
150 you use "make install" to install shared libraries, pcregrep and pcretest are
151 automatically re-built to use the newly installed shared libraries before being
152 installed themselves. However, the versions left in the source directory still
153 use the uninstalled libraries.
155 To build PCRE using static libraries only you must use --disable-shared when
156 configuring it. For example
158 ./configure --prefix=/usr/gnu --disable-shared
160 Then run "make" in the usual way. Similarly, you can use --disable-static to
161 build only shared libraries.
164 Cross-compiling on a Unix-like system
165 -------------------------------------
167 You can specify CC and CFLAGS in the normal way to the "configure" command, in
168 order to cross-compile PCRE for some other host. However, during the building
169 process, the dftables.c source file is compiled *and run* on the local host, in
170 order to generate the default character tables (the chartables.c file). It
171 therefore needs to be compiled with the local compiler, not the cross compiler.
172 You can do this by specifying HOST_CC (and if necessary HOST_CFLAGS) when
173 calling the "configure" command. If they are not specified, they default to the
174 values of CC and CFLAGS.
177 Building on non-Unix systems
178 ----------------------------
180 For a non-Unix system, read the comments in the file NON-UNIX-USE. PCRE has
181 been compiled on Windows systems and on Macintoshes, but I don't know the
182 details because I don't use those systems. It should be straightforward to
183 build PCRE on any system that has a Standard C compiler, because it uses only
184 Standard C functions.
187 Testing PCRE
188 ------------
190 To test PCRE on a Unix system, run the RunTest script that is created by the
191 configuring process. (This can also be run by "make runtest", "make check", or
192 "make test".) For other systems, see the instruction in NON-UNIX-USE.
194 The script runs the pcretest test program (which is documented in its own man
195 page) on each of the testinput files (in the testdata directory) in turn,
196 and compares the output with the contents of the corresponding testoutput file.
197 A file called testtry is used to hold the output from pcretest. To run pcretest
198 on just one of the test files, give its number as an argument to RunTest, for
199 example:
201 RunTest 2
203 The first file can also be fed directly into the perltest script to check that
204 Perl gives the same results. The only difference you should see is in the first
205 few lines, where the Perl version is given instead of the PCRE version.
207 The second set of tests check pcre_fullinfo(), pcre_info(), pcre_study(),
208 pcre_copy_substring(), pcre_get_substring(), pcre_get_substring_list(), error
209 detection, and run-time flags that are specific to PCRE, as well as the POSIX
210 wrapper API. It also uses the debugging flag to check some of the internals of
211 pcre_compile().
213 If you build PCRE with a locale setting that is not the standard C locale, the
214 character tables may be different (see next paragraph). In some cases, this may
215 cause failures in the second set of tests. For example, in a locale where the
216 isprint() function yields TRUE for characters in the range 128-255, the use of
217 [:isascii:] inside a character class defines a different set of characters, and
218 this shows up in this test as a difference in the compiled code, which is being
219 listed for checking. Where the comparison test output contains [\x00-\x7f] the
220 test will contain [\x00-\xff], and similarly in some other cases. This is not a
221 bug in PCRE.
223 The third set of tests checks pcre_maketables(), the facility for building a
224 set of character tables for a specific locale and using them instead of the
225 default tables. The tests make use of the "fr" (French) locale. Before running
226 the test, the script checks for the presence of this locale by running the
227 "locale" command. If that command fails, or if it doesn't include "fr" in the
228 list of available locales, the third test cannot be run, and a comment is
229 output to say why. If running this test produces instances of the error
231 ** Failed to set locale "fr"
233 in the comparison output, it means that locale is not available on your system,
234 despite being listed by "locale". This does not mean that PCRE is broken.
236 The fourth test checks the UTF-8 support. It is not run automatically unless
237 PCRE is built with UTF-8 support. To do this you must set --enable-utf8 when
238 running "configure". This file can be also fed directly to the perltest script,
239 provided you are running Perl 5.8 or higher. (For Perl 5.6, a small patch,
240 commented in the script, can be be used.)
242 The fifth and final file tests error handling with UTF-8 encoding, and internal
243 UTF-8 features of PCRE that are not relevant to Perl.
246 Character tables
247 ----------------
249 PCRE uses four tables for manipulating and identifying characters. The final
250 argument of the pcre_compile() function is a pointer to a block of memory
251 containing the concatenated tables. A call to pcre_maketables() can be used to
252 generate a set of tables in the current locale. If the final argument for
253 pcre_compile() is passed as NULL, a set of default tables that is built into
254 the binary is used.
256 The source file called chartables.c contains the default set of tables. This is
257 not supplied in the distribution, but is built by the program dftables
258 (compiled from dftables.c), which uses the ANSI C character handling functions
259 such as isalnum(), isalpha(), isupper(), islower(), etc. to build the table
260 sources. This means that the default C locale which is set for your system will
261 control the contents of these default tables. You can change the default tables
262 by editing chartables.c and then re-building PCRE. If you do this, you should
263 probably also edit Makefile to ensure that the file doesn't ever get
264 re-generated.
266 The first two 256-byte tables provide lower casing and case flipping functions,
267 respectively. The next table consists of three 32-byte bit maps which identify
268 digits, "word" characters, and white space, respectively. These are used when
269 building 32-byte bit maps that represent character classes.
271 The final 256-byte table has bits indicating various character types, as
272 follows:
274 1 white space character
275 2 letter
276 4 decimal digit
277 8 hexadecimal digit
278 16 alphanumeric or '_'
279 128 regular expression metacharacter or binary zero
281 You should not alter the set of characters that contain the 128 bit, as that
282 will cause PCRE to malfunction.
285 Manifest
286 --------
288 The distribution should contain the following files:
290 (A) The actual source files of the PCRE library functions and their
291 headers:
293 dftables.c auxiliary program for building chartables.c
294 get.c )
295 maketables.c )
296 study.c ) source of
297 pcre.c ) the functions
298 pcreposix.c )
299 printint.c )
300 pcre.in "source" for the header for the external API; pcre.h
301 is built from this by "configure"
302 pcreposix.h header for the external POSIX wrapper API
303 internal.h header for internal use
304 config.in template for config.h, which is built by configure
306 (B) Auxiliary files:
308 AUTHORS information about the author of PCRE
309 ChangeLog log of changes to the code
310 INSTALL generic installation instructions
311 LICENCE conditions for the use of PCRE
312 COPYING the same, using GNU's standard name
313 Makefile.in template for Unix Makefile, which is built by configure
314 NEWS important changes in this release
315 NON-UNIX-USE notes on building PCRE on non-Unix systems
316 README this file
317 RunTest.in template for a Unix shell script for running tests
318 config.guess ) files used by libtool,
319 config.sub ) used only when building a shared library
320 configure a configuring shell script (built by autoconf)
321 configure.in the autoconf input used to build configure
322 doc/Tech.Notes notes on the encoding
323 doc/*.3 man page sources for the PCRE functions
324 doc/*.1 man page sources for pcregrep and pcretest
325 doc/html/* HTML documentation
326 doc/pcre.txt plain text version of the man pages
327 doc/pcretest.txt plain text documentation of test program
328 doc/perltest.txt plain text documentation of Perl test program
329 install-sh a shell script for installing files
330 ltmain.sh file used to build a libtool script
331 pcretest.c comprehensive test program
332 pcredemo.c simple demonstration of coding calls to PCRE
333 perltest Perl test program
334 pcregrep.c source of a grep utility that uses PCRE
335 pcre-config.in source of script which retains PCRE information
336 testdata/testinput1 test data, compatible with Perl
337 testdata/testinput2 test data for error messages and non-Perl things
338 testdata/testinput3 test data for locale-specific tests
339 testdata/testinput4 test data for UTF-8 tests compatible with Perl
340 testdata/testinput5 test data for other UTF-8 tests
341 testdata/testoutput1 test results corresponding to testinput1
342 testdata/testoutput2 test results corresponding to testinput2
343 testdata/testoutput3 test results corresponding to testinput3
344 testdata/testoutput4 test results corresponding to testinput4
345 testdata/testoutput5 test results corresponding to testinput5
347 (C) Auxiliary files for Win32 DLL
349 dll.mk
350 pcre.def
352 (D) Auxiliary file for VPASCAL
354 makevp.bat
356 Philip Hazel <ph10@cam.ac.uk>
357 February 2003

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