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1  README file for PCRE (Perl-compatible regular expressions)  README file for PCRE (Perl-compatible regular expression library)
2  ----------------------------------------------------------  -----------------------------------------------------------------
3    
4  The distribution should contain the following files:  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    ChangeLog         log of changes to the code  Please read the NEWS file if you are upgrading from a previous release.
   Makefile          for building PCRE  
   Performance       notes on performance  
   README            this file  
   Tech.Notes        notes on the encoding  
   pcre.3            man page for the functions  
   pcreposix.3       man page for the POSIX wrapper API  
   maketables.c      auxiliary program for building chartables.c  
   study.c           ) source of  
   pcre.c            )   the functions  
   pcreposix.c       )  
   pcre.h            header for the external API  
   pcreposix.h       header for the external POSIX wrapper API  
   internal.h        header for internal use  
   pcretest.c        test program  
   pgrep.1           man page for pgrep  
   pgrep.c           source of a grep utility that uses PCRE  
   perltest          Perl test program  
   testinput         test data, compatible with Perl  
   testinput2        test data for error messages and non-Perl things  
   testoutput        test results corresponding to testinput  
   testoutput2       test results corresponding to testinput2  
   
 To build PCRE, edit Makefile for your system (it is a fairly simple make file)  
 and then run it. It builds a two libraries called libpcre.a and libpcreposix.a,  
 a test program called pcretest, and the pgrep command.  
   
 To test PCRE, run pcretest on the file testinput, and compare the output with  
 the contents of testoutput. There should be no differences. For example:  
   
   pcretest testinput some.file  
   diff some.file testoutput  
   
 Do the same with testinput2, comparing the output with testoutput2, but this  
 time using the -i flag for pcretest, i.e.  
   
   pcretest -i testinput2 some.file  
   diff some.file testoutput2  
   
 The make target "runtest" runs both these tests, using the file "testtry" to  
 store the intermediate output, deleting it at the end if all goes well.  
   
 There are two sets of tests because the first set can also be fed directly into  
 the perltest program to check that Perl gives the same results. The second set  
 of tests check pcre_info(), pcre_study(), error detection and run-time flags  
 that are specific to PCRE, as well as the POSIX wrapper API.  
   
 To install PCRE, copy libpcre.a to any suitable library directory (e.g.  
 /usr/local/lib), pcre.h to any suitable include directory (e.g.  
 /usr/local/include), and pcre.3 to any suitable man directory (e.g.  
 /usr/local/man/man3).  
   
 To install the pgrep command, copy it to any suitable binary directory, (e.g.  
 /usr/local/bin) and pgrep.1 to any suitable man directory (e.g.  
 /usr/local/man/man1).  
9    
10  PCRE has its own native API, but a set of "wrapper" functions that are based on  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.a. Note that this  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  just provides a POSIX calling interface to PCRE: the regular expressions
13  themselves still follow Perl syntax and semantics. The header file  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  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  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  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.  uses the POSIX API, it will have to be renamed or pointed at by a link.
18    
19    If you are using the POSIX interface to PCRE and there is already a POSIX regex
20    library installed on your system, you must take care when linking programs to
21    ensure that they link with PCRE's libpcreposix library. Otherwise they may pick
22    up the "real" POSIX functions of the same name.
23    
24    
25    Contributions by users of PCRE
26    ------------------------------
27    
28    You can find contributions from PCRE users in the directory
29    
30      ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/Contrib
31    
32    where there is also a README file giving brief descriptions of what they are.
33    Several of them provide support for compiling PCRE on various flavours of
34    Windows systems (I myself do not use Windows). Some are complete in themselves;
35    others are pointers to URLs containing relevant files.
36    
37    
38    Building PCRE on a Unix-like system
39    -----------------------------------
40    
41    To build PCRE on a Unix-like system, first run the "configure" command from the
42    PCRE distribution directory, with your current directory set to the directory
43    where you want the files to be created. This command is a standard GNU
44    "autoconf" configuration script, for which generic instructions are supplied in
45    INSTALL.
46    
47    Most commonly, people build PCRE within its own distribution directory, and in
48    this case, on many systems, just running "./configure" is sufficient, but the
49    usual methods of changing standard defaults are available. For example,
50    
51    CFLAGS='-O2 -Wall' ./configure --prefix=/opt/local
52    
53    specifies that the C compiler should be run with the flags '-O2 -Wall' instead
54    of the default, and that "make install" should install PCRE under /opt/local
55    instead of the default /usr/local.
56    
57    If you want to build in a different directory, just run "configure" with that
58    directory as current. For example, suppose you have unpacked the PCRE source
59    into /source/pcre/pcre-xxx, but you want to build it in /build/pcre/pcre-xxx:
60    
61    cd /build/pcre/pcre-xxx
62    /source/pcre/pcre-xxx/configure
63    
64    There are some optional features that can be included or omitted from the PCRE
65    library. You can read more about them in the pcrebuild man page.
66    
67    . If you want to make use of the support for UTF-8 character strings in PCRE,
68      you must add --enable-utf8 to the "configure" command. Without it, the code
69      for handling UTF-8 is not included in the library. (Even when included, it
70      still has to be enabled by an option at run time.)
71    
72    . You can build PCRE to recognized CR or NL as the newline character, instead
73      of whatever your compiler uses for "\n", by adding --newline-is-cr or
74      --newline-is-nl to the "configure" command, respectively. Only do this if you
75      really understand what you are doing. On traditional Unix-like systems, the
76      newline character is NL.
77    
78    . When called via the POSIX interface, PCRE uses malloc() to get additional
79      storage for processing capturing parentheses if there are more than 10 of
80      them. You can increase this threshold by setting, for example,
81    
82      --with-posix-malloc-threshold=20
83    
84      on the "configure" command.
85    
86    . PCRE has a counter which can be set to limit the amount of resources it uses.
87      If the limit is exceeded during a match, the match fails. The default is ten
88      million. You can change the default by setting, for example,
89    
90      --with-match-limit=500000
91    
92      on the "configure" command. This is just the default; individual calls to
93      pcre_exec() can supply their own value. There is discussion on the pcreapi
94      man page.
95    
96    . The default maximum compiled pattern size is around 64K. You can increase
97      this by adding --with-link-size=3 to the "configure" command. You can
98      increase it even more by setting --with-link-size=4, but this is unlikely
99      ever to be necessary. If you build PCRE with an increased link size, test 2
100      (and 5 if you are using UTF-8) will fail. Part of the output of these tests
101      is a representation of the compiled pattern, and this changes with the link
102      size.
103    
104    . You can build PCRE so that its match() function does not call itself
105      recursively. Instead, it uses blocks of data from the heap via special
106      functions pcre_stack_malloc() and pcre_stack_free() to save data that would
107      otherwise be saved on the stack. To build PCRE like this, use
108    
109      --disable-stack-for-recursion
110    
111      on the "configure" command. PCRE runs more slowly in this mode, but it may be
112      necessary in environments with limited stack sizes.
113    
114    The "configure" script builds five files:
115    
116    . libtool is a script that builds shared and/or static libraries
117    . Makefile is built by copying Makefile.in and making substitutions.
118    . config.h is built by copying config.in and making substitutions.
119    . pcre-config is built by copying pcre-config.in and making substitutions.
120    . RunTest is a script for running tests
121    
122    Once "configure" has run, you can run "make". It builds two libraries called
123    libpcre and libpcreposix, a test program called pcretest, and the pcregrep
124    command. You can use "make install" to copy these, the public header files
125    pcre.h and pcreposix.h, and the man pages to appropriate live directories on
126    your system, in the normal way.
127    
128    Running "make install" also installs the command pcre-config, which can be used
129    to recall information about the PCRE configuration and installation. For
130    example,
131    
132      pcre-config --version
133    
134    prints the version number, and
135    
136     pcre-config --libs
137    
138    outputs information about where the library is installed. This command can be
139    included in makefiles for programs that use PCRE, saving the programmer from
140    having to remember too many details.
141    
142    
143    Shared libraries on Unix-like systems
144    -------------------------------------
145    
146    The default distribution builds PCRE as two shared libraries and two static
147    libraries, as long as the operating system supports shared libraries. Shared
148    library support relies on the "libtool" script which is built as part of the
149    "configure" process.
150    
151    The libtool script is used to compile and link both shared and static
152    libraries. They are placed in a subdirectory called .libs when they are newly
153    built. The programs pcretest and pcregrep are built to use these uninstalled
154    libraries (by means of wrapper scripts in the case of shared libraries). When
155    you use "make install" to install shared libraries, pcregrep and pcretest are
156    automatically re-built to use the newly installed shared libraries before being
157    installed themselves. However, the versions left in the source directory still
158    use the uninstalled libraries.
159    
160    To build PCRE using static libraries only you must use --disable-shared when
161    configuring it. For example
162    
163    ./configure --prefix=/usr/gnu --disable-shared
164    
165    Then run "make" in the usual way. Similarly, you can use --disable-static to
166    build only shared libraries.
167    
168    
169    Cross-compiling on a Unix-like system
170    -------------------------------------
171    
172    You can specify CC and CFLAGS in the normal way to the "configure" command, in
173    order to cross-compile PCRE for some other host. However, during the building
174    process, the dftables.c source file is compiled *and run* on the local host, in
175    order to generate the default character tables (the chartables.c file). It
176    therefore needs to be compiled with the local compiler, not the cross compiler.
177    You can do this by specifying CC_FOR_BUILD (and if necessary CFLAGS_FOR_BUILD)
178    when calling the "configure" command. If they are not specified, they default
179    to the values of CC and CFLAGS.
180    
181    
182    Building on non-Unix systems
183    ----------------------------
184    
185    For a non-Unix system, read the comments in the file NON-UNIX-USE, though if
186    the system supports the use of "configure" and "make" you may be able to build
187    PCRE in the same way as for Unix systems.
188    
189    PCRE has been compiled on Windows systems and on Macintoshes, but I don't know
190    the details because I don't use those systems. It should be straightforward to
191    build PCRE on any system that has a Standard C compiler, because it uses only
192    Standard C functions.
193    
194    
195    Testing PCRE
196    ------------
197    
198    To test PCRE on a Unix system, run the RunTest script that is created by the
199    configuring process. (This can also be run by "make runtest", "make check", or
200    "make test".) For other systems, see the instructions in NON-UNIX-USE.
201    
202    The script runs the pcretest test program (which is documented in its own man
203    page) on each of the testinput files (in the testdata directory) in turn,
204    and compares the output with the contents of the corresponding testoutput file.
205    A file called testtry is used to hold the output from pcretest. To run pcretest
206    on just one of the test files, give its number as an argument to RunTest, for
207    example:
208    
209      RunTest 2
210    
211    The first file can also be fed directly into the perltest script to check that
212    Perl gives the same results. The only difference you should see is in the first
213    few lines, where the Perl version is given instead of the PCRE version.
214    
215    The second set of tests check pcre_fullinfo(), pcre_info(), pcre_study(),
216    pcre_copy_substring(), pcre_get_substring(), pcre_get_substring_list(), error
217    detection, and run-time flags that are specific to PCRE, as well as the POSIX
218    wrapper API. It also uses the debugging flag to check some of the internals of
219    pcre_compile().
220    
221    If you build PCRE with a locale setting that is not the standard C locale, the
222    character tables may be different (see next paragraph). In some cases, this may
223    cause failures in the second set of tests. For example, in a locale where the
224    isprint() function yields TRUE for characters in the range 128-255, the use of
225    [:isascii:] inside a character class defines a different set of characters, and
226    this shows up in this test as a difference in the compiled code, which is being
227    listed for checking. Where the comparison test output contains [\x00-\x7f] the
228    test will contain [\x00-\xff], and similarly in some other cases. This is not a
229    bug in PCRE.
230    
231    The third set of tests checks pcre_maketables(), the facility for building a
232    set of character tables for a specific locale and using them instead of the
233    default tables. The tests make use of the "fr_FR" (French) locale. Before
234    running the test, the script checks for the presence of this locale by running
235    the "locale" command. If that command fails, or if it doesn't include "fr_FR"
236    in the list of available locales, the third test cannot be run, and a comment
237    is output to say why. If running this test produces instances of the error
238    
239      ** Failed to set locale "fr_FR"
240    
241    in the comparison output, it means that locale is not available on your system,
242    despite being listed by "locale". This does not mean that PCRE is broken.
243    
244    The fourth test checks the UTF-8 support. It is not run automatically unless
245    PCRE is built with UTF-8 support. To do this you must set --enable-utf8 when
246    running "configure". This file can be also fed directly to the perltest script,
247    provided you are running Perl 5.8 or higher. (For Perl 5.6, a small patch,
248    commented in the script, can be be used.)
249    
250    The fifth and final file tests error handling with UTF-8 encoding, and internal
251    UTF-8 features of PCRE that are not relevant to Perl.
252    
253    
254  Character tables  Character tables
255  ----------------  ----------------
256    
257  PCRE uses four tables for manipulating and identifying characters. These are  PCRE uses four tables for manipulating and identifying characters. The final
258  compiled from a source file called chartables.c. This is not supplied in  argument of the pcre_compile() function is a pointer to a block of memory
259  the distribution, but is built by the program maketables (compiled from  containing the concatenated tables. A call to pcre_maketables() can be used to
260  maketables.c), which uses the ANSI C character handling functions such as  generate a set of tables in the current locale. If the final argument for
261  isalnum(), isalpha(), isupper(), islower(), etc. to build the table sources.  pcre_compile() is passed as NULL, a set of default tables that is built into
262  This means that the default C locale set in your system may affect the contents  the binary is used.
263  of the tables. You can change the tables by editing chartables.c and then  
264  re-building PCRE. If you do this, you should probably also edit Makefile to  The source file called chartables.c contains the default set of tables. This is
265  ensure that the file doesn't ever get re-generated.  not supplied in the distribution, but is built by the program dftables
266    (compiled from dftables.c), which uses the ANSI C character handling functions
267  The first two tables pcre_lcc[] and pcre_fcc[] provide lower casing and a  such as isalnum(), isalpha(), isupper(), islower(), etc. to build the table
268  case flipping functions, respectively. The pcre_cbits[] table consists of four  sources. This means that the default C locale which is set for your system will
269  32-byte bit maps which identify digits, letters, "word" characters, and white  control the contents of these default tables. You can change the default tables
270  space, respectively. These are used when building 32-byte bit maps that  by editing chartables.c and then re-building PCRE. If you do this, you should
271  represent character classes.  probably also edit Makefile to ensure that the file doesn't ever get
272    re-generated.
273    
274    The first two 256-byte tables provide lower casing and case flipping functions,
275    respectively. The next table consists of three 32-byte bit maps which identify
276    digits, "word" characters, and white space, respectively. These are used when
277    building 32-byte bit maps that represent character classes.
278    
279  The pcre_ctypes[] table has bits indicating various character types, as  The final 256-byte table has bits indicating various character types, as
280  follows:  follows:
281    
282      1   white space character      1   white space character
# Line 102  You should not alter the set of characte Line 290  You should not alter the set of characte
290  will cause PCRE to malfunction.  will cause PCRE to malfunction.
291    
292    
293  The pcretest program  Manifest
294  --------------------  --------
295    
296    The distribution should contain the following files:
297    
298    (A) The actual source files of the PCRE library functions and their
299        headers:
300    
301      dftables.c            auxiliary program for building chartables.c
302      get.c                 )
303      maketables.c          )
304      study.c               ) source of
305      pcre.c                )   the functions
306      pcreposix.c           )
307      printint.c            )
308      pcre.in               "source" for the header for the external API; pcre.h
309                              is built from this by "configure"
310      pcreposix.h           header for the external POSIX wrapper API
311      internal.h            header for internal use
312      config.in             template for config.h, which is built by configure
313    
314    (B) Auxiliary files:
315    
316      AUTHORS               information about the author of PCRE
317      ChangeLog             log of changes to the code
318      INSTALL               generic installation instructions
319      LICENCE               conditions for the use of PCRE
320      COPYING               the same, using GNU's standard name
321      Makefile.in           template for Unix Makefile, which is built by configure
322      NEWS                  important changes in this release
323      NON-UNIX-USE          notes on building PCRE on non-Unix systems
324      README                this file
325      RunTest.in            template for a Unix shell script for running tests
326      config.guess          ) files used by libtool,
327      config.sub            )   used only when building a shared library
328      configure             a configuring shell script (built by autoconf)
329      configure.in          the autoconf input used to build configure
330      doc/Tech.Notes        notes on the encoding
331      doc/*.3               man page sources for the PCRE functions
332      doc/*.1               man page sources for pcregrep and pcretest
333      doc/html/*            HTML documentation
334      doc/pcre.txt          plain text version of the man pages
335      doc/pcretest.txt      plain text documentation of test program
336      doc/perltest.txt      plain text documentation of Perl test program
337      install-sh            a shell script for installing files
338      ltmain.sh             file used to build a libtool script
339      pcretest.c            comprehensive test program
340      pcredemo.c            simple demonstration of coding calls to PCRE
341      perltest              Perl test program
342      pcregrep.c            source of a grep utility that uses PCRE
343      pcre-config.in        source of script which retains PCRE information
344      testdata/testinput1   test data, compatible with Perl
345      testdata/testinput2   test data for error messages and non-Perl things
346      testdata/testinput3   test data for locale-specific tests
347      testdata/testinput4   test data for UTF-8 tests compatible with Perl
348      testdata/testinput5   test data for other UTF-8 tests
349      testdata/testoutput1  test results corresponding to testinput1
350      testdata/testoutput2  test results corresponding to testinput2
351      testdata/testoutput3  test results corresponding to testinput3
352      testdata/testoutput4  test results corresponding to testinput4
353      testdata/testoutput5  test results corresponding to testinput5
354    
355    (C) Auxiliary files for Win32 DLL
356    
357      dll.mk
358      pcre.def
359    
360  This program is intended for testing PCRE, but it can also be used for  (D) Auxiliary file for VPASCAL
 experimenting with regular expressions.  
361    
362  If it is given two filename arguments, it reads from the first and writes to    makevp.bat
 the second. If it is given only one filename argument, it reads from that file  
 and writes to stdout. Otherwise, it reads from stdin and writes to stdout, and  
 prompts for each line of input.  
   
 The program handles any number of sets of input on a single input file. Each  
 set starts with a regular expression, and continues with any number of data  
 lines to be matched against the pattern. An empty line signals the end of the  
 set. The regular expressions are given enclosed in any non-alphameric  
 delimiters, for example  
   
   /(a|bc)x+yz/  
   
 and may be followed by i, m, s, or x to set the PCRE_CASELESS, PCRE_MULTILINE,  
 PCRE_DOTALL, or PCRE_EXTENDED options, respectively. These options have the  
 same effect as they do in Perl.  
   
 There are also some upper case options that do not match Perl options: /A, /E,  
 and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.  
 The /D option is a PCRE debugging feature. It causes the internal form of  
 compiled regular expressions to be output after compilation. The /S option  
 causes pcre_study() to be called after the expression has been compiled, and  
 the results used when the expression is matched. If /I is present as well as  
 /S, then pcre_study() is called with the PCRE_CASELESS option.  
   
 Finally, the /P option causes pcretest to call PCRE via the POSIX wrapper API  
 rather than its native API. When this is done, all other options except /i and  
 /m are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is set if /m  
 is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always, and  
 PCRE_DOTALL unless REG_NEWLINE is set.  
   
 A regular expression can extend over several lines of input; the newlines are  
 included in it. See the testinput file for many examples.  
   
 Before each data line is passed to pcre_exec(), leading and trailing whitespace  
 is removed, and it is then scanned for \ escapes. The following are recognized:  
   
   \a     alarm (= BEL)  
   \b     backspace  
   \e     escape  
   \f     formfeed  
   \n     newline  
   \r     carriage return  
   \t     tab  
   \v     vertical tab  
   \nnn   octal character (up to 3 octal digits)  
   \xhh   hexadecimal character (up to 2 hex digits)  
   
   \A     pass the PCRE_ANCHORED option to pcre_exec()  
   \B     pass the PCRE_NOTBOL option to pcre_exec()  
   \E     pass the PCRE_DOLLAR_ENDONLY option to pcre_exec()  
   \I     pass the PCRE_CASELESS option to pcre_exec()  
   \M     pass the PCRE_MULTILINE option to pcre_exec()  
   \S     pass the PCRE_DOTALL option to pcre_exec()  
   \Odd   set the size of the output vector passed to pcre_exec() to dd  
            (any number of decimal digits)  
   \Z     pass the PCRE_NOTEOL option to pcre_exec()  
   
 A backslash followed by anything else just escapes the anything else. If the  
 very last character is a backslash, it is ignored. This gives a way of passing  
 an empty line as data, since a real empty line terminates the data input.  
   
 If /P was present on the regex, causing the POSIX wrapper API to be used, only  
 \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to  
 regexec() respectively.  
   
 When a match succeeds, pcretest outputs the list of identified substrings that  
 pcre_exec() returns, starting with number 0 for the string that matched the  
 whole pattern. Here is an example of an interactive pcretest run.  
   
   $ pcretest  
   Testing Perl-Compatible Regular Expressions  
   PCRE version 0.90 08-Sep-1997  
   
       re> /^abc(\d+)/  
     data> abc123  
    0: abc123  
    1: 123  
     data> xyz  
   No match  
   
 Note that while patterns can be continued over several lines (a plain ">"  
 prompt is used for continuations), data lines may not. However newlines can be  
 included in data by means of the \n escape.  
   
 If the -p option is given to pcretest, it is equivalent to adding /P to each  
 regular expression: the POSIX wrapper API is used to call PCRE. None of the  
 following flags has any effect in this case.  
   
 If the option -d is given to pcretest, it is equivalent to adding /D to each  
 regular expression: the internal form is output after compilation.  
   
 If the option -i (for "information") is given to pcretest, it calls pcre_info()  
 after compiling an expression, and outputs the information it gets back. If the  
 pattern is studied, the results of that are also output.  
   
 If the option -s is given to pcretest, it outputs the size of each compiled  
 pattern after it has been compiled.  
   
 If the -t option is given, each compile, study, and match is run 2000 times  
 while being timed, and the resulting time per compile or match is output in  
 milliseconds. Do not set -t with -s, because you will then get the size output  
 2000 times and the timing will be distorted.  
   
   
   
 The perltest program  
 --------------------  
   
 The perltest program tests Perl's regular expressions; it has the same  
 specification as pcretest, and so can be given identical input, except that  
 input patterns can be followed only by Perl's lower case options.  
   
 The data lines are processed as Perl strings, so if they contain $ or @  
 characters, these have to be escaped. For this reason, all such characters in  
 the testinput file are escaped so that it can be used for perltest as well as  
 for pcretest, and the special upper case options such as /A that pcretest  
 recognizes are not used in this file. The output should be identical, apart  
 from the initial identifying banner.  
   
 The testinput2 file is not suitable for feeding to Perltest, since it does  
 make use of the special upper case options and escapes that pcretest uses to  
 test additional features of PCRE.  
363    
364  Philip Hazel <ph10@cam.ac.uk>  Philip Hazel <ph10@cam.ac.uk>
365  October 1997  December 2003

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