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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 latest release of PCRE is always available from
 *           IMPORTANT FOR THOSE UPGRADING FROM VERSIONS BEFORE 2.00           *  
 *                                                                             *  
 * Please note that there has been a change in the API such that a larger      *  
 * ovector is required at matching time, to provide some additional workspace. *  
 * The new man page has details. This change was necessary in order to support *  
 * some of the new functionality in Perl 5.005.                                *  
 *                                                                             *  
 *           IMPORTANT FOR THOSE UPGRADING FROM VERSION 2.00                   *  
 *                                                                             *  
 * Another (I hope this is the last!) change has been made to the API for the  *  
 * pcre_compile() function. An additional argument has been added to make it   *  
 * possible to pass over a pointer to character tables built in the current    *  
 * locale by pcre_maketables(). To use the default tables, this new arguement  *  
 * should be passed as NULL.                                                   *  
 *                                                                             *  
 *           IMPORTANT FOR THOSE UPGRADING FROM VERSION 2.05                   *  
 *                                                                             *  
 * Yet another (and again I hope this really is the last) change has been made *  
 * to the API for the pcre_exec() function. An additional argument has been    *  
 * added to make it possible to start the match other than at the start of the *  
 * subject string. This is important if there are lookbehinds. The new man     *  
 * page has the details, but you just want to convert existing programs, all   *  
 * you need to do is to stick in a new fifth argument to pcre_exec(), with a   *  
 * value of zero. For example, change                                          *  
 *                                                                             *  
 *   pcre_exec(pattern, extra, subject, length, options, ovec, ovecsize)       *  
 * to                                                                          *  
 *   pcre_exec(pattern, extra, subject, length, 0, options, ovec, ovecsize)    *  
 *******************************************************************************  
5    
6      ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre-xxx.tar.gz
7    
8  The distribution should contain the following files:  Please read the NEWS file if you are upgrading from a previous release.
9    
10    
11    Building PCRE on a Unix system
12    ------------------------------
13    
14    To build PCRE on a Unix system, run the "configure" command in the PCRE
15    distribution directory. This is a standard GNU "autoconf" configuration script,
16    for which generic instructions are supplied in INSTALL. On many systems just
17    running "./configure" is sufficient, but the usual methods of changing standard
18    defaults are available. For example
19    
20    ChangeLog         log of changes to the code  CFLAGS='-O2 -Wall' ./configure --prefix=/opt/local
21    LICENCE           conditions for the use of PCRE  
22    Makefile          for building PCRE in Unix systems  specifies that the C compiler should be run with the flags '-O2 -Wall' instead
23    README            this file  of the default, and that "make install" should install PCRE under /opt/local
24    RunTest           a Unix shell script for running tests  instead of the default /usr/local. The "configure" script builds thre files:
25    Tech.Notes        notes on the encoding  
26    pcre.3            man page source for the functions  . Makefile is built by copying Makefile.in and making substitutions.
27    pcre.3.txt        plain text version  . config.h is built by copying config.in and making substitutions.
28    pcre.3.html       HTML version  . pcre-config is built by copying pcre-config.in and making substitutions.
29    pcreposix.3       man page source for the POSIX wrapper API  
30    pcreposix.3.txt   plain text version  Once "configure" has run, you can run "make". It builds two libraries called
31    pcreposix.3.HTML  HTML version  libpcre and libpcreposix, a test program called pcretest, and the pgrep
   dftables.c        auxiliary program for building chartables.c  
   get.c             )  
   maketables.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 source for pgrep  
   pgrep.1.txt       plain text version  
   pgrep.1.HTML      HTML version  
   pgrep.c           source of a grep utility that uses PCRE  
   perltest          Perl test program  
   testinput1        test data, compatible with Perl 5.004 and 5.005  
   testinput2        test data for error messages and non-Perl things  
   testinput3        test data, compatible with Perl 5.005  
   testinput4        test data for locale-specific tests  
   testoutput1       test results corresponding to testinput1  
   testoutput2       test results corresponding to testinput2  
   testoutput3       test results corresponding to testinput3  
   testoutput4       test results corresponding to testinput4  
   dll.mk            for Win32 DLL  
   pcre.def          ditto  
   
 To build PCRE on a Unix system, first edit Makefile for your system. It is a  
 fairly simple make file, and there are some comments near the top, after the  
 text "On a Unix system". Then run "make". It builds two libraries called  
 libpcre.a and libpcreposix.a, a test program called pcretest, and the pgrep  
32  command. You can use "make install" to copy these, and the public header file  command. You can use "make install" to copy these, and the public header file
33  pcre.h, to appropriate live directories on your system. These installation  pcre.h, to appropriate live directories on your system, in the normal way.
34  directories are defined at the top of the Makefile, and you should edit them if  
35  necessary.  Running "make install" also installs the command pcre-config, which can be used
36    to recall information about the PCRE configuration and installation. For
37  For a non-Unix system, read the comments at the top of Makefile, which give  example,
38  some hints on what needs to be done. PCRE has been compiled on Windows systems  
39  and on Macintoshes, but I don't know the details as I don't use those systems.    pcre-config --version
40  It should be straightforward to build PCRE on any system that has a Standard C  
41  compiler.  prints the version number, and
42    
43  Some help in building a Win32 DLL of PCRE in GnuWin32 environments was   pcre-config --libs
44  contributed by Paul.Sokolovsky@technologist.com. These environments are  
45  Mingw32 (http://www.xraylith.wisc.edu/~khan/software/gnu-win32/) and  outputs information about where the library is installed. This command can be
46  CygWin  (http://sourceware.cygnus.com/cygwin/). Paul comments:  included in makefiles for programs that use PCRE, saving the programmer from
47    having to remember too many details.
48    For CygWin, set CFLAGS=-mno-cygwin, and do 'make dll'. You'll get  
49    pcre.dll (containing pcreposix also), libpcre.dll.a, and dynamically  
50    linked pgrep and pcretest. If you have /bin/sh, run RunTest (three  Shared libraries on Unix systems
51    main test go ok, locale not supported).  --------------------------------
52    
53  To test PCRE, run the RunTest script in the pcre directory. This can also be  The default distribution builds PCRE as two shared libraries. This support is
54  run by "make runtest". It runs the pcretest test program (which is documented  new and experimental and may not work on all systems. It relies on the
55  below) on each of the testinput files in turn, and compares the output with the  "libtool" scripts - these are distributed with PCRE. It should build a
56  contents of the corresponding testoutput file. A file called testtry is used to  "libtool" script and use this to compile and link shared libraries, which are
57  hold the output from pcretest. To run pcretest on just one of the test files,  placed in a subdirectory called .libs. The programs pcretest and pgrep are
58  give its number as an argument to RunTest, for example:  built to use these uninstalled libraries by means of wrapper scripts. When you
59    use "make install" to install shared libraries, pgrep and pcretest are
60    automatically re-built to use the newly installed libraries. However, only
61    pgrep is installed, as pcretest is really just a test program.
62    
63    To build PCRE using static libraries you must use --disable-shared when
64    configuring it. For example
65    
66    ./configure --prefix=/usr/gnu --disable-shared
67    
68    Then run "make" in the usual way.
69    
70    
71    Building on non-Unix systems
72    ----------------------------
73    
74    For a non-Unix system, read the comments in the file NON-UNIX-USE. PCRE has
75    been compiled on Windows systems and on Macintoshes, but I don't know the
76    details because I don't use those systems. It should be straightforward to
77    build PCRE on any system that has a Standard C compiler, because it uses only
78    Standard C functions.
79    
80    
81    Testing PCRE
82    ------------
83    
84    To test PCRE on a Unix system, run the RunTest script in the pcre directory.
85    (This can also be run by "make runtest" or "make check".) For other systems,
86    see the instruction in NON-UNIX-USE.
87    
88    The script runs the pcretest test program (which is documented in
89    doc/pcretest.txt) on each of the testinput files (in the testdata directory) in
90    turn, and compares the output with the contents of the corresponding testoutput
91    file. A file called testtry is used to hold the output from pcretest. To run
92    pcretest on just one of the test files, give its number as an argument to
93    RunTest, for example:
94    
95    RunTest 3    RunTest 3
96    
# Line 179  You should not alter the set of characte Line 166  You should not alter the set of characte
166  will cause PCRE to malfunction.  will cause PCRE to malfunction.
167    
168    
169  The pcretest program  Manifest
170  --------------------  --------
171    
172  This program is intended for testing PCRE, but it can also be used for  The distribution should contain the following files:
 experimenting with regular expressions.  
173    
174  If it is given two filename arguments, it reads from the first and writes to  (A) The actual source files of the PCRE library functions and their
175  the second. If it is given only one filename argument, it reads from that file      headers:
176  and writes to stdout. Otherwise, it reads from stdin and writes to stdout, and  
177  prompts for each line of input.    dftables.c            auxiliary program for building chartables.c
178      get.c                 )
179  The program handles any number of sets of input on a single input file. Each    maketables.c          )
180  set starts with a regular expression, and continues with any number of data    study.c               ) source of
181  lines to be matched against the pattern. An empty line signals the end of the    pcre.c                )   the functions
182  set. The regular expressions are given enclosed in any non-alphameric    pcreposix.c           )
183  delimiters other than backslash, for example    pcre.in               "source" for the header for the external API; pcre.h
184                              is built from this by "configure"
185    /(a|bc)x+yz/    pcreposix.h           header for the external POSIX wrapper API
186      internal.h            header for internal use
187  White space before the initial delimiter is ignored. A regular expression may    config.in             template for config.h, which is built by configure
188  be continued over several input lines, in which case the newline characters are  
189  included within it. See the testinput files for many examples. It is possible  (B) Auxiliary files:
190  to include the delimiter within the pattern by escaping it, for example  
191      AUTHORS               information about the author of PCRE
192    /abc\/def/    ChangeLog             log of changes to the code
193      INSTALL               generic installation instructions
194  If you do so, the escape and the delimiter form part of the pattern, but since    LICENCE               conditions for the use of PCRE
195  delimiters are always non-alphameric, this does not affect its interpretation.    COPYING               the same, using GNU's standard name
196  If the terminating delimiter is immediately followed by a backslash, for    Makefile.in           template for Unix Makefile, which is built by configure
197  example,    NEWS                  important changes in this release
198      NON-UNIX-USE          notes on building PCRE on non-Unix systems
199      README                this file
200      RunTest               a Unix shell script for running tests
201      config.guess          ) files used by libtool,
202      config.sub            )   used only when building a shared library
203      configure             a configuring shell script (built by autoconf)
204      configure.in          the autoconf input used to build configure
205      doc/Tech.Notes        notes on the encoding
206      doc/pcre.3            man page source for the PCRE functions
207      doc/pcre.html         HTML version
208      doc/pcre.txt          plain text version
209      doc/pcreposix.3       man page source for the POSIX wrapper API
210      doc/pcreposix.html    HTML version
211      doc/pcreposix.txt     plain text version
212      doc/pcretest.txt      documentation of test program
213      doc/perltest.txt      documentation of Perl test program
214      doc/pgrep.1           man page source for the pgrep utility
215      doc/pgrep.html        HTML version
216      doc/pgrep.txt         plain text version
217      install-sh            a shell script for installing files
218      ltconfig              ) files used to build "libtool",
219      ltmain.sh             )   used only when building a shared library
220      pcretest.c            test program
221      perltest              Perl test program
222      pgrep.c               source of a grep utility that uses PCRE
223      pcre-config.in        source of script which retains PCRE information
224      testdata/testinput1   test data, compatible with Perl 5.004 and 5.005
225      testdata/testinput2   test data for error messages and non-Perl things
226      testdata/testinput3   test data, compatible with Perl 5.005
227      testdata/testinput4   test data for locale-specific tests
228      testdata/testoutput1  test results corresponding to testinput1
229      testdata/testoutput2  test results corresponding to testinput2
230      testdata/testoutput3  test results corresponding to testinput3
231      testdata/testoutput4  test results corresponding to testinput4
232    
233    /abc/\  (C) Auxiliary files for Win32 DLL
234    
235  then a backslash is added to the end of the pattern. This is done to provide a    dll.mk
236  way of testing the error condition that arises if a pattern finishes with a    pcre.def
 backslash, because  
   
   /abc\/  
   
 is interpreted as the first line of a pattern that starts with "abc/", causing  
 pcretest to read the next line as a continuation of the regular expression.  
   
 The pattern may be followed by i, m, s, or x to set the PCRE_CASELESS,  
 PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. For  
 example:  
   
   /caseless/i  
   
 These modifier letters have the same effect as they do in Perl. There are  
 others which set PCRE options that do not correspond to anything in Perl: /A,  
 /E, and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.  
   
 Searching for all possible matches within each subject string can be requested  
 by the /g or /G modifier. After finding a match, PCRE is called again to search  
 the remainder of the subject string. The difference between /g and /G is that  
 the former uses the startoffset argument to pcre_exec() to start searching at  
 a new point within the entire string (which is in effect what Perl does),  
 whereas the latter passes over a shortened substring. This makes a difference  
 to the matching process if the pattern begins with a lookbehind assertion  
 (including \b or \B).  
   
 If any call to pcre_exec() in a /g or /G sequence matches an empty string, the  
 next call is done with the PCRE_NOTEMPTY flag set so that it cannot match an  
 empty string again. This imitates the way Perl handles such cases when using  
 the /g modifier or the split() function.  
   
 There are a number of other modifiers for controlling the way pcretest  
 operates.  
   
 The /+ modifier requests that as well as outputting the substring that matched  
 the entire pattern, pcretest should in addition output the remainder of the  
 subject string. This is useful for tests where the subject contains multiple  
 copies of the same substring.  
   
 The /L modifier must be followed directly by the name of a locale, for example,  
   
   /pattern/Lfr  
   
 For this reason, it must be the last modifier letter. The given locale is set,  
 pcre_maketables() is called to build a set of character tables for the locale,  
 and this is then passed to pcre_compile() when compiling the regular  
 expression. Without an /L modifier, NULL is passed as the tables pointer; that  
 is, /L applies only to the expression on which it appears.  
   
 The /I modifier requests that pcretest output information about the compiled  
 expression (whether it is anchored, has a fixed first character, and so on). It  
 does this by calling pcre_info() after compiling an expression, and outputting  
 the information it gets back. If the pattern is studied, the results of that  
 are also output.  
   
 The /D modifier is a PCRE debugging feature, which also assumes /I. It causes  
 the internal form of compiled regular expressions to be output after  
 compilation.  
   
 The /S modifier causes pcre_study() to be called after the expression has been  
 compiled, and the results used when the expression is matched.  
   
 The /M modifier causes the size of memory block used to hold the compiled  
 pattern to be output.  
   
 Finally, the /P modifier causes pcretest to call PCRE via the POSIX wrapper API  
 rather than its native API. When this is done, all other modifiers except /i,  
 /m, and /+ 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.  
   
 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()  
   \Cdd   call pcre_copy_substring() for substring dd after a successful match  
            (any decimal number less than 32)  
   \Gdd   call pcre_get_substring() for substring dd after a successful match  
            (any decimal number less than 32)  
   \L     call pcre_get_substringlist() after a successful match  
   \N     pass the PCRE_NOTEMPTY 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 captured 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  
   PCRE version 2.06 08-Jun-1999  
   
     re> /^abc(\d+)/  
   data> abc123  
    0: abc123  
    1: 123  
   data> xyz  
   No match  
   
 If the strings contain any non-printing characters, they are output as \0x  
 escapes. If the pattern has the /+ modifier, then the output for substring 0 is  
 followed by the the rest of the subject string, identified by "0+" like this:  
   
     re> /cat/+  
   data> cataract  
    0: cat  
    0+ aract  
   
 If the pattern has the /g or /G modifier, the results of successive matching  
 attempts are output in sequence, like this:  
   
     re> /\Bi(\w\w)/g  
   data> Mississippi  
    0: iss  
    1: ss  
    0: iss  
    1: ss  
    0: ipp  
    1: pp  
   
 "No match" is output only if the first match attempt fails.  
   
 If any of \C, \G, or \L are present in a data line that is successfully  
 matched, the substrings extracted by the convenience functions are output with  
 C, G, or L after the string number instead of a colon. This is in addition to  
 the normal full list. The string length (that is, the return from the  
 extraction function) is given in parentheses after each string for \C and \G.  
   
 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 is given to pcretest, it is equivalent to adding /I to each  
 regular expression: information about the compiled pattern is given after  
 compilation.  
   
 If the option -m is given to pcretest, it outputs the size of each compiled  
 pattern after it has been compiled. It is equivalent to adding /M to each  
 regular expression. For compatibility with earlier versions of pcretest, -s is  
 a synonym for -m.  
   
 If the -t option is given, each compile, study, and match is run 20000 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  
 20000 times and the timing will be distorted. If you want to change the number  
 of repetitions used for timing, edit the definition of LOOPREPEAT at the top of  
 pcretest.c  
   
   
   
 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 modifiers. The  
 contents of testinput1 and testinput3 meet this condition.  
   
 The data lines are processed as Perl double-quoted strings, so if they contain  
 " \ $ or @ characters, these have to be escaped. For this reason, all such  
 characters in testinput1 and testinput3 are escaped so that they can be used  
 for perltest as well as for pcretest, and the special upper case modifiers such  
 as /A that pcretest recognizes are not used in these files. The output should  
 be identical, apart from the initial identifying banner.  
   
 The testinput2 and testinput4 files are not suitable for feeding to perltest,  
 since they do make use of the special upper case modifiers and escapes that  
 pcretest uses to test some features of PCRE. The first of these files also  
 contains malformed regular expressions, in order to check that PCRE diagnoses  
 them correctly.  
237    
238  Philip Hazel <ph10@cam.ac.uk>  Philip Hazel <ph10@cam.ac.uk>
239  July 1999  February 2000

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