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1  README file for PCRE (Perl-compatible regular expressions)  README file for PCRE (Perl-compatible regular expressions)
2  ----------------------------------------------------------  ----------------------------------------------------------
3    
4    *******************************************************************************
5    *           IMPORTANT FOR THOSE UPGRADING FROM VERSIONS BEFORE 2.00           *
6    *                                                                             *
7    * Please note that there has been a change in the API such that a larger      *
8    * ovector is required at matching time, to provide some additional workspace. *
9    * The new man page has details. This change was necessary in order to support *
10    * some of the new functionality in Perl 5.005.                                *
11    *                                                                             *
12    *           IMPORTANT FOR THOSE UPGRADING FROM VERSION 2.00                   *
13    *                                                                             *
14    * Another (I hope this is the last!) change has been made to the API for the  *
15    * pcre_compile() function. An additional argument has been added to make it   *
16    * possible to pass over a pointer to character tables built in the current    *
17    * locale by pcre_maketables(). To use the default tables, this new arguement  *
18    * should be passed as NULL.                                                   *
19    *                                                                             *
20    *           IMPORTANT FOR THOSE UPGRADING FROM VERSION 2.05                   *
21    *                                                                             *
22    * Yet another (and again I hope this really is the last) change has been made *
23    * to the API for the pcre_exec() function. An additional argument has been    *
24    * added to make it possible to start the match other than at the start of the *
25    * subject string. This is important if there are lookbehinds. The new man     *
26    * page has the details, but you just want to convert existing programs, all   *
27    * you need to do is to stick in a new fifth argument to pcre_exec(), with a   *
28    * value of zero. For example, change                                          *
29    *                                                                             *
30    *   pcre_exec(pattern, extra, subject, length, options, ovec, ovecsize)       *
31    * to                                                                          *
32    *   pcre_exec(pattern, extra, subject, length, 0, options, ovec, ovecsize)    *
33    *******************************************************************************
34    
35    
36  The distribution should contain the following files:  The distribution should contain the following files:
37    
38    ChangeLog         log of changes to the code    ChangeLog         log of changes to the code
39    Makefile          for building PCRE    LICENCE           conditions for the use of PCRE
40    Performance       notes on performance    Makefile          for building PCRE in Unix systems
41    README            this file    README            this file
42      RunTest           a Unix shell script for running tests
43    Tech.Notes        notes on the encoding    Tech.Notes        notes on the encoding
44    pcre.3            man page for the functions    pcre.3            man page source for the functions
45    pcreposix.3       man page for the POSIX wrapper API    pcre.3.txt        plain text version
46    maketables.c      auxiliary program for building chartables.c    pcre.3.html       HTML version
47      pcreposix.3       man page source for the POSIX wrapper API
48      pcreposix.3.txt   plain text version
49      pcreposix.3.HTML  HTML version
50      dftables.c        auxiliary program for building chartables.c
51      get.c             )
52      maketables.c      )
53    study.c           ) source of    study.c           ) source of
54    pcre.c            )   the functions    pcre.c            )   the functions
55    pcreposix.c       )    pcreposix.c       )
# Line 18  The distribution should contain the foll Line 57  The distribution should contain the foll
57    pcreposix.h       header for the external POSIX wrapper API    pcreposix.h       header for the external POSIX wrapper API
58    internal.h        header for internal use    internal.h        header for internal use
59    pcretest.c        test program    pcretest.c        test program
60    pgrep.1           man page for pgrep    pgrep.1           man page source for pgrep
61      pgrep.1.txt       plain text version
62      pgrep.1.HTML      HTML version
63    pgrep.c           source of a grep utility that uses PCRE    pgrep.c           source of a grep utility that uses PCRE
64    perltest          Perl test program    perltest          Perl test program
65    testinput         test data, compatible with Perl    testinput1        test data, compatible with Perl 5.004 and 5.005
66    testinput2        test data for error messages and non-Perl things    testinput2        test data for error messages and non-Perl things
67    testoutput        test results corresponding to testinput    testinput3        test data, compatible with Perl 5.005
68      testinput4        test data for locale-specific tests
69      testoutput1       test results corresponding to testinput1
70    testoutput2       test results corresponding to testinput2    testoutput2       test results corresponding to testinput2
71      testoutput3       test results corresponding to testinput3
72      testoutput4       test results corresponding to testinput4
73      dll.mk            for Win32 DLL
74      pcre.def          ditto
75    
76    To build PCRE on a Unix system, first edit Makefile for your system. It is a
77    fairly simple make file, and there are some comments near the top, after the
78    text "On a Unix system". Then run "make". It builds two libraries called
79    libpcre.a and libpcreposix.a, a test program called pcretest, and the pgrep
80    command. You can use "make install" to copy these, and the public header file
81    pcre.h, to appropriate live directories on your system. These installation
82    directories are defined at the top of the Makefile, and you should edit them if
83    necessary.
84    
85    For a non-Unix system, read the comments at the top of Makefile, which give
86    some hints on what needs to be done. PCRE has been compiled on Windows systems
87    and on Macintoshes, but I don't know the details as I don't use those systems.
88    It should be straightforward to build PCRE on any system that has a Standard C
89    compiler.
90    
91    Some help in building a Win32 DLL of PCRE in GnuWin32 environments was
92    contributed by Paul.Sokolovsky@technologist.com. These environments are
93    Mingw32 (http://www.xraylith.wisc.edu/~khan/software/gnu-win32/) and
94    CygWin  (http://sourceware.cygnus.com/cygwin/). Paul comments:
95    
96      For CygWin, set CFLAGS=-mno-cygwin, and do 'make dll'. You'll get
97      pcre.dll (containing pcreposix also), libpcre.dll.a, and dynamically
98      linked pgrep and pcretest. If you have /bin/sh, run RunTest (three
99      main test go ok, locale not supported).
100    
101    To test PCRE, run the RunTest script in the pcre directory. This can also be
102    run by "make runtest". It runs the pcretest test program (which is documented
103    below) on each of the testinput files in turn, and compares the output with the
104    contents of the corresponding testoutput file. A file called testtry is used to
105    hold the output from pcretest. To run pcretest on just one of the test files,
106    give its number as an argument to RunTest, for example:
107    
108      RunTest 3
109    
110    The first and third test files can also be fed directly into the perltest
111    script to check that Perl gives the same results. The third file requires the
112    additional features of release 5.005, which is why it is kept separate from the
113    main test input, which needs only Perl 5.004. In the long run, when 5.005 is
114    widespread, these two test files may get amalgamated.
115    
116    The second set of tests check pcre_info(), pcre_study(), pcre_copy_substring(),
117    pcre_get_substring(), pcre_get_substring_list(), error detection and run-time
118    flags that are specific to PCRE, as well as the POSIX wrapper API.
119    
120    The fourth set of tests checks pcre_maketables(), the facility for building a
121    set of character tables for a specific locale and using them instead of the
122    default tables. The tests make use of the "fr" (French) locale. Before running
123    the test, the script checks for the presence of this locale by running the
124    "locale" command. If that command fails, or if it doesn't include "fr" in the
125    list of available locales, the fourth test cannot be run, and a comment is
126    output to say why. If running this test produces instances of the error
127    
128      ** Failed to set locale "fr"
129    
130  To build PCRE, edit Makefile for your system (it is a fairly simple make file)  in the comparison output, it means that locale is not available on your system,
131  and then run it. It builds a two libraries called libpcre.a and libpcreposix.a,  despite being listed by "locale". This does not mean that PCRE is broken.
 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 /tmp/anything  
   diff /tmp/anything 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 /tmp/anything  
   diff /tmp/anything testoutput2  
   
 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).  
132    
133  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
134  the POSIX API are also supplied in the library libpcreposix.a. Note that this  the POSIX API are also supplied in the library libpcreposix.a. Note that this
# Line 63  themselves still follow Perl syntax and Line 137  themselves still follow Perl syntax and
137  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
138  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
139  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
140  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.
141    
142    
143  Character tables  Character tables
144  ----------------  ----------------
145    
146  PCRE uses four tables for manipulating and identifying characters. These are  PCRE uses four tables for manipulating and identifying characters. The final
147  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
148  the distribution, but is built by the program maketables (compiled from  containing the concatenated tables. A call to pcre_maketables() can be used to
149  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
150  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
151  This means that the default C locale set in your system may affect the contents  the binary is used.
152  of the tables. You can change the tables by editing chartables.c and then  
153  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
154  ensure that the file doesn't ever get re-generated.  not supplied in the distribution, but is built by the program dftables
155    (compiled from dftables.c), which uses the ANSI C character handling functions
156  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
157  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
158  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
159  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
160  represent character classes.  probably also edit Makefile to ensure that the file doesn't ever get
161    re-generated.
162    
163    The first two 256-byte tables provide lower casing and case flipping functions,
164    respectively. The next table consists of three 32-byte bit maps which identify
165    digits, "word" characters, and white space, respectively. These are used when
166    building 32-byte bit maps that represent character classes.
167    
168  The pcre_ctypes[] table has bits indicating various character types, as  The final 256-byte table has bits indicating various character types, as
169  follows:  follows:
170    
171      1   white space character      1   white space character
# Line 114  The program handles any number of sets o Line 194  The program handles any number of sets o
194  set starts with a regular expression, and continues with any number of data  set starts with a regular expression, and continues with any number of data
195  lines to be matched against the pattern. An empty line signals the end of the  lines to be matched against the pattern. An empty line signals the end of the
196  set. The regular expressions are given enclosed in any non-alphameric  set. The regular expressions are given enclosed in any non-alphameric
197  delimiters, for example  delimiters other than backslash, for example
198    
199    /(a|bc)x+yz/    /(a|bc)x+yz/
200    
201  and may be followed by i, m, s, or x to set the PCRE_CASELESS, PCRE_MULTILINE,  White space before the initial delimiter is ignored. A regular expression may
202  PCRE_DOTALL, or PCRE_EXTENDED options, respectively. These options have the  be continued over several input lines, in which case the newline characters are
203  same effect as they do in Perl.  included within it. See the testinput files for many examples. It is possible
204    to include the delimiter within the pattern by escaping it, for example
205  There are also some upper case options that do not match Perl options: /A, /E,  
206  and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.    /abc\/def/
207  The /D option is a PCRE debugging feature. It causes the internal form of  
208  compiled regular expressions to be output after compilation. The /S option  If you do so, the escape and the delimiter form part of the pattern, but since
209  causes pcre_study() to be called after the expression has been compiled, and  delimiters are always non-alphameric, this does not affect its interpretation.
210  the results used when the expression is matched. If /I is present as well as  If the terminating delimiter is immediately followed by a backslash, for
211  /S, then pcre_study() is called with the PCRE_CASELESS option.  example,
212    
213  Finally, the /P option causes pcretest to call PCRE via the POSIX wrapper API    /abc/\
214  rather than its native API. When this is done, all other options except /i and  
215  /m are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is set if /m  then a backslash is added to the end of the pattern. This is done to provide a
216  is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always, and  way of testing the error condition that arises if a pattern finishes with a
217  PCRE_DOTALL unless REG_NEWLINE is set.  backslash, because
218    
219  A regular expression can extend over several lines of input; the newlines are    /abc\/
220  included in it. See the testinput file for many examples.  
221    is interpreted as the first line of a pattern that starts with "abc/", causing
222    pcretest to read the next line as a continuation of the regular expression.
223    
224    The pattern may be followed by i, m, s, or x to set the PCRE_CASELESS,
225    PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. For
226    example:
227    
228      /caseless/i
229    
230    These modifier letters have the same effect as they do in Perl. There are
231    others which set PCRE options that do not correspond to anything in Perl: /A,
232    /E, and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.
233    
234    Searching for all possible matches within each subject string can be requested
235    by the /g or /G modifier. After finding a match, PCRE is called again to search
236    the remainder of the subject string. The difference between /g and /G is that
237    the former uses the startoffset argument to pcre_exec() to start searching at
238    a new point within the entire string (which is in effect what Perl does),
239    whereas the latter passes over a shortened substring. This makes a difference
240    to the matching process if the pattern begins with a lookbehind assertion
241    (including \b or \B).
242    
243    If any call to pcre_exec() in a /g or /G sequence matches an empty string, the
244    next call is done with the PCRE_NOTEMPTY flag set so that it cannot match an
245    empty string again. This imitates the way Perl handles such cases when using
246    the /g modifier or the split() function.
247    
248    There are a number of other modifiers for controlling the way pcretest
249    operates.
250    
251    The /+ modifier requests that as well as outputting the substring that matched
252    the entire pattern, pcretest should in addition output the remainder of the
253    subject string. This is useful for tests where the subject contains multiple
254    copies of the same substring.
255    
256    The /L modifier must be followed directly by the name of a locale, for example,
257    
258      /pattern/Lfr
259    
260    For this reason, it must be the last modifier letter. The given locale is set,
261    pcre_maketables() is called to build a set of character tables for the locale,
262    and this is then passed to pcre_compile() when compiling the regular
263    expression. Without an /L modifier, NULL is passed as the tables pointer; that
264    is, /L applies only to the expression on which it appears.
265    
266    The /I modifier requests that pcretest output information about the compiled
267    expression (whether it is anchored, has a fixed first character, and so on). It
268    does this by calling pcre_info() after compiling an expression, and outputting
269    the information it gets back. If the pattern is studied, the results of that
270    are also output.
271    
272    The /D modifier is a PCRE debugging feature, which also assumes /I. It causes
273    the internal form of compiled regular expressions to be output after
274    compilation.
275    
276    The /S modifier causes pcre_study() to be called after the expression has been
277    compiled, and the results used when the expression is matched.
278    
279    The /M modifier causes the size of memory block used to hold the compiled
280    pattern to be output.
281    
282    Finally, the /P modifier causes pcretest to call PCRE via the POSIX wrapper API
283    rather than its native API. When this is done, all other modifiers except /i,
284    /m, and /+ are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is
285    set if /m is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always,
286    and PCRE_DOTALL unless REG_NEWLINE is set.
287    
288  Before each data line is passed to pcre_exec(), leading and trailing whitespace  Before each data line is passed to pcre_exec(), leading and trailing whitespace
289  is removed, and it is then scanned for \ escapes. The following are recognized:  is removed, and it is then scanned for \ escapes. The following are recognized:
# Line 155  is removed, and it is then scanned for \ Line 301  is removed, and it is then scanned for \
301    
302    \A     pass the PCRE_ANCHORED option to pcre_exec()    \A     pass the PCRE_ANCHORED option to pcre_exec()
303    \B     pass the PCRE_NOTBOL option to pcre_exec()    \B     pass the PCRE_NOTBOL option to pcre_exec()
304    \E     pass the PCRE_DOLLAR_ENDONLY option to pcre_exec()    \Cdd   call pcre_copy_substring() for substring dd after a successful match
305    \I     pass the PCRE_CASELESS option to pcre_exec()             (any decimal number less than 32)
306    \M     pass the PCRE_MULTILINE option to pcre_exec()    \Gdd   call pcre_get_substring() for substring dd after a successful match
307    \S     pass the PCRE_DOTALL option to pcre_exec()             (any decimal number less than 32)
308      \L     call pcre_get_substringlist() after a successful match
309      \N     pass the PCRE_NOTEMPTY option to pcre_exec()
310    \Odd   set the size of the output vector passed to pcre_exec() to dd    \Odd   set the size of the output vector passed to pcre_exec() to dd
311             (any number of decimal digits)             (any number of decimal digits)
312    \Z     pass the PCRE_NOTEOL option to pcre_exec()    \Z     pass the PCRE_NOTEOL option to pcre_exec()
# Line 171  If /P was present on the regex, causing Line 319  If /P was present on the regex, causing
319  \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to  \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to
320  regexec() respectively.  regexec() respectively.
321    
322  When a match succeeds, pcretest outputs the list of identified substrings that  When a match succeeds, pcretest outputs the list of captured substrings that
323  pcre_exec() returns, starting with number 0 for the string that matched the  pcre_exec() returns, starting with number 0 for the string that matched the
324  whole pattern. Here is an example of an interactive pcretest run.  whole pattern. Here is an example of an interactive pcretest run.
325    
326    $ pcretest    $ pcretest
327    Testing Perl-Compatible Regular Expressions    PCRE version 2.06 08-Jun-1999
   PCRE version 0.90 08-Sep-1997  
328    
329        re> /^abc(\d+)/      re> /^abc(\d+)/
330      data> abc123    data> abc123
331     0: abc123     0: abc123
332     1: 123     1: 123
333      data> xyz    data> xyz
334    No match    No match
335    
336    If the strings contain any non-printing characters, they are output as \0x
337    escapes. If the pattern has the /+ modifier, then the output for substring 0 is
338    followed by the the rest of the subject string, identified by "0+" like this:
339    
340        re> /cat/+
341      data> cataract
342       0: cat
343       0+ aract
344    
345    If the pattern has the /g or /G modifier, the results of successive matching
346    attempts are output in sequence, like this:
347    
348        re> /\Bi(\w\w)/g
349      data> Mississippi
350       0: iss
351       1: ss
352       0: iss
353       1: ss
354       0: ipp
355       1: pp
356    
357    "No match" is output only if the first match attempt fails.
358    
359    If any of \C, \G, or \L are present in a data line that is successfully
360    matched, the substrings extracted by the convenience functions are output with
361    C, G, or L after the string number instead of a colon. This is in addition to
362    the normal full list. The string length (that is, the return from the
363    extraction function) is given in parentheses after each string for \C and \G.
364    
365  Note that while patterns can be continued over several lines (a plain ">"  Note that while patterns can be continued over several lines (a plain ">"
366  prompt is used for continuations), data lines may not. However newlines can be  prompt is used for continuations), data lines may not. However newlines can be
367  included in data by means of the \n escape.  included in data by means of the \n escape.
# Line 197  following flags has any effect in this c Line 373  following flags has any effect in this c
373  If the option -d is given to pcretest, it is equivalent to adding /D to each  If the option -d is given to pcretest, it is equivalent to adding /D to each
374  regular expression: the internal form is output after compilation.  regular expression: the internal form is output after compilation.
375    
376  If the option -i (for "information") is given to pcretest, it calls pcre_info()  If the option -i is given to pcretest, it is equivalent to adding /I to each
377  after compiling an expression, and outputs the information it gets back. If the  regular expression: information about the compiled pattern is given after
378  pattern is studied, the results of that are also output.  compilation.
379    
380  If the option -s is given to pcretest, it outputs the size of each compiled  If the option -m is given to pcretest, it outputs the size of each compiled
381  pattern after it has been compiled.  pattern after it has been compiled. It is equivalent to adding /M to each
382    regular expression. For compatibility with earlier versions of pcretest, -s is
383    a synonym for -m.
384    
385  If the -t option is given, each compile, study, and match is run 2000 times  If the -t option is given, each compile, study, and match is run 20000 times
386  while being timed, and the resulting time per compile or match is output in  while being timed, and the resulting time per compile or match is output in
387  milliseconds. Do not set -t with -s, because you will then get the size output  milliseconds. Do not set -t with -s, because you will then get the size output
388  2000 times and the timing will be distorted.  20000 times and the timing will be distorted. If you want to change the number
389    of repetitions used for timing, edit the definition of LOOPREPEAT at the top of
390    pcretest.c
391    
392    
393    
# Line 216  The perltest program Line 396  The perltest program
396    
397  The perltest program tests Perl's regular expressions; it has the same  The perltest program tests Perl's regular expressions; it has the same
398  specification as pcretest, and so can be given identical input, except that  specification as pcretest, and so can be given identical input, except that
399  input patterns can be followed only by Perl's lower case options.  input patterns can be followed only by Perl's lower case modifiers. The
400    contents of testinput1 and testinput3 meet this condition.
401    
402  The data lines are processed as Perl strings, so if they contain $ or @  The data lines are processed as Perl double-quoted strings, so if they contain
403  characters, these have to be escaped. For this reason, all such characters in  " \ $ or @ characters, these have to be escaped. For this reason, all such
404  the testinput file are escaped so that it can be used for perltest as well as  characters in testinput1 and testinput3 are escaped so that they can be used
405  for pcretest, and the special upper case options such as /A that pcretest  for perltest as well as for pcretest, and the special upper case modifiers such
406  recognizes are not used in this file. The output should be identical, apart  as /A that pcretest recognizes are not used in these files. The output should
407  from the initial identifying banner.  be identical, apart from the initial identifying banner.
408    
409  The testinput2 file is not suitable for feeding to Perltest, since it does  The testinput2 and testinput4 files are not suitable for feeding to perltest,
410  make use of the special upper case options and escapes that pcretest uses to  since they do make use of the special upper case modifiers and escapes that
411  test additional features of PCRE.  pcretest uses to test some features of PCRE. The first of these files also
412    contains malformed regular expressions, in order to check that PCRE diagnoses
413    them correctly.
414    
415  Philip Hazel <ph10@cam.ac.uk>  Philip Hazel <ph10@cam.ac.uk>
416  October 1997  July 1999
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