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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    
74    To build PCRE on a Unix system, first edit Makefile for your system. It is a
75    fairly simple make file, and there are some comments near the top, after the
76    text "On a Unix system". Then run "make". It builds two libraries called
77    libpcre.a and libpcreposix.a, a test program called pcretest, and the pgrep
78    command. You can use "make install" to copy these, and the public header file
79    pcre.h, to appropriate live directories on your system. These installation
80    directories are defined at the top of the Makefile, and you should edit them if
81    necessary.
82    
83    For a non-Unix system, read the comments at the top of Makefile, which give
84    some hints on what needs to be done. PCRE has been compiled on Windows systems
85    and on Macintoshes, but I don't know the details as I don't use those systems.
86    It should be straightforward to build PCRE on any system that has a Standard C
87    compiler.
88    
89    To test PCRE, run the RunTest script in the pcre directory. This can also be
90    run by "make runtest". It runs the pcretest test program (which is documented
91    below) on each of the testinput files in turn, and compares the output with the
92    contents of the corresponding testoutput file. A file called testtry is used to
93    hold the output from pcretest. To run pcretest on just one of the test files,
94    give its number as an argument to RunTest, for example:
95    
96      RunTest 3
97    
98    The first and third test files can also be fed directly into the perltest
99    script to check that Perl gives the same results. The third file requires the
100    additional features of release 5.005, which is why it is kept separate from the
101    main test input, which needs only Perl 5.004. In the long run, when 5.005 is
102    widespread, these two test files may get amalgamated.
103    
104    The second set of tests check pcre_info(), pcre_study(), pcre_copy_substring(),
105    pcre_get_substring(), pcre_get_substring_list(), error detection and run-time
106    flags that are specific to PCRE, as well as the POSIX wrapper API.
107    
108    The fourth set of tests checks pcre_maketables(), the facility for building a
109    set of character tables for a specific locale and using them instead of the
110    default tables. The tests make use of the "fr" (French) locale. Before running
111    the test, the script checks for the presence of this locale by running the
112    "locale" command. If that command fails, or if it doesn't include "fr" in the
113    list of available locales, the fourth test cannot be run, and a comment is
114    output to say why. If running this test produces instances of the error
115    
116      ** Failed to set locale "fr"
117    
118  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,
119  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).  
120    
121  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
122  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 125  themselves still follow Perl syntax and
125  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
126  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
127  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
128  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.
129    
130    
131  Character tables  Character tables
132  ----------------  ----------------
133    
134  PCRE uses four tables for manipulating and identifying characters. These are  PCRE uses four tables for manipulating and identifying characters. The final
135  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
136  the distribution, but is built by the program maketables (compiled from  containing the concatenated tables. A call to pcre_maketables() can be used to
137  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
138  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
139  This means that the default C locale set in your system may affect the contents  the binary is used.
140  of the tables. You can change the tables by editing chartables.c and then  
141  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
142  ensure that the file doesn't ever get re-generated.  not supplied in the distribution, but is built by the program dftables
143    (compiled from dftables.c), which uses the ANSI C character handling functions
144  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
145  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
146  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
147  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
148  represent character classes.  probably also edit Makefile to ensure that the file doesn't ever get
149    re-generated.
150    
151    The first two 256-byte tables provide lower casing and case flipping functions,
152    respectively. The next table consists of three 32-byte bit maps which identify
153    digits, "word" characters, and white space, respectively. These are used when
154    building 32-byte bit maps that represent character classes.
155    
156  The pcre_ctypes[] table has bits indicating various character types, as  The final 256-byte table has bits indicating various character types, as
157  follows:  follows:
158    
159      1   white space character      1   white space character
# Line 114  The program handles any number of sets o Line 182  The program handles any number of sets o
182  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
183  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
184  set. The regular expressions are given enclosed in any non-alphameric  set. The regular expressions are given enclosed in any non-alphameric
185  delimiters, for example  delimiters other than backslash, for example
186    
187    /(a|bc)x+yz/    /(a|bc)x+yz/
188    
189  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
190  PCRE_DOTALL, or PCRE_EXTENDED options, respectively. These options have the  be continued over several input lines, in which case the newline characters are
191  same effect as they do in Perl.  included within it. See the testinput files for many examples. It is possible
192    to include the delimiter within the pattern by escaping it, for example
193  There are also some upper case options that do not match Perl options: /A, /E,  
194  and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.    /abc\/def/
195  The /D option is a PCRE debugging feature. It causes the internal form of  
196  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
197  causes pcre_study() to be called after the expression has been compiled, and  delimiters are always non-alphameric, this does not affect its interpretation.
198  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
199  /S, then pcre_study() is called with the PCRE_CASELESS option.  example,
200    
201  Finally, the /P option causes pcretest to call PCRE via the POSIX wrapper API    /abc/\
202  rather than its native API. When this is done, all other options except /i and  
203  /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
204  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
205  PCRE_DOTALL unless REG_NEWLINE is set.  backslash, because
206    
207  A regular expression can extend over several lines of input; the newlines are    /abc\/
208  included in it. See the testinput file for many examples.  
209    is interpreted as the first line of a pattern that starts with "abc/", causing
210    pcretest to read the next line as a continuation of the regular expression.
211    
212    The pattern may be followed by i, m, s, or x to set the PCRE_CASELESS,
213    PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. For
214    example:
215    
216      /caseless/i
217    
218    These modifier letters have the same effect as they do in Perl. There are
219    others which set PCRE options that do not correspond to anything in Perl: /A,
220    /E, and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.
221    
222    Searching for all possible matches within each subject string can be requested
223    by the /g or /G modifier. The /g modifier behaves similarly to the way it does
224    in Perl. After finding a match, PCRE is called again to search the remainder of
225    the subject string. The difference between /g and /G is that the former uses
226    the start_offset argument to pcre_exec() to start searching at a new point
227    within the entire string, whereas the latter passes over a shortened substring.
228    This makes a difference to the matching process if the pattern begins with a
229    lookbehind assertion (including \b or \B).
230    
231    There are a number of other modifiers for controlling the way pcretest
232    operates.
233    
234    The /+ modifier requests that as well as outputting the substring that matched
235    the entire pattern, pcretest should in addition output the remainder of the
236    subject string. This is useful for tests where the subject contains multiple
237    copies of the same substring.
238    
239    The /L modifier must be followed directly by the name of a locale, for example,
240    
241      /pattern/Lfr
242    
243    For this reason, it must be the last modifier letter. The given locale is set,
244    pcre_maketables() is called to build a set of character tables for the locale,
245    and this is then passed to pcre_compile() when compiling the regular
246    expression. Without an /L modifier, NULL is passed as the tables pointer; that
247    is, /L applies only to the expression on which it appears.
248    
249    The /I modifier requests that pcretest output information about the compiled
250    expression (whether it is anchored, has a fixed first character, and so on). It
251    does this by calling pcre_info() after compiling an expression, and outputting
252    the information it gets back. If the pattern is studied, the results of that
253    are also output.
254    
255    The /D modifier is a PCRE debugging feature, which also assumes /I. It causes
256    the internal form of compiled regular expressions to be output after
257    compilation.
258    
259    The /S modifier causes pcre_study() to be called after the expression has been
260    compiled, and the results used when the expression is matched.
261    
262    The /M modifier causes the size of memory block used to hold the compiled
263    pattern to be output.
264    
265    Finally, the /P modifier causes pcretest to call PCRE via the POSIX wrapper API
266    rather than its native API. When this is done, all other modifiers except /i,
267    /m, and /+ are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is
268    set if /m is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always,
269    and PCRE_DOTALL unless REG_NEWLINE is set.
270    
271  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
272  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 284  is removed, and it is then scanned for \
284    
285    \A     pass the PCRE_ANCHORED option to pcre_exec()    \A     pass the PCRE_ANCHORED option to pcre_exec()
286    \B     pass the PCRE_NOTBOL option to pcre_exec()    \B     pass the PCRE_NOTBOL option to pcre_exec()
287    \E     pass the PCRE_DOLLAR_ENDONLY option to pcre_exec()    \Cdd   call pcre_copy_substring() for substring dd after a successful match
288    \I     pass the PCRE_CASELESS option to pcre_exec()             (any decimal number less than 32)
289    \M     pass the PCRE_MULTILINE option to pcre_exec()    \Gdd   call pcre_get_substring() for substring dd after a successful match
290    \S     pass the PCRE_DOTALL option to pcre_exec()             (any decimal number less than 32)
291      \L     call pcre_get_substringlist() after a successful match
292      \N     pass the PCRE_NOTEMPTY option to pcre_exec()
293    \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
294             (any number of decimal digits)             (any number of decimal digits)
295    \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 302  If /P was present on the regex, causing
302  \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
303  regexec() respectively.  regexec() respectively.
304    
305  When a match succeeds, pcretest outputs the list of identified substrings that  When a match succeeds, pcretest outputs the list of captured substrings that
306  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
307  whole pattern. Here is an example of an interactive pcretest run.  whole pattern. Here is an example of an interactive pcretest run.
308    
309    $ pcretest    $ pcretest
310    Testing Perl-Compatible Regular Expressions    PCRE version 2.06 08-Jun-1999
   PCRE version 0.90 08-Sep-1997  
311    
312        re> /^abc(\d+)/      re> /^abc(\d+)/
313      data> abc123    data> abc123
314     0: abc123     0: abc123
315     1: 123     1: 123
316      data> xyz    data> xyz
317    No match    No match
318    
319    If the strings contain any non-printing characters, they are output as \0x
320    escapes. If the pattern has the /+ modifier, then the output for substring 0 is
321    followed by the the rest of the subject string, identified by "0+" like this:
322    
323        re> /cat/+
324      data> cataract
325       0: cat
326       0+ aract
327    
328    If the pattern has the /g or /G modifier, the results of successive matching
329    attempts are output in sequence, like this:
330    
331        re> /\Bi(\w\w)/g
332      data> Mississippi
333       0: iss
334       1: ss
335       0: iss
336       1: ss
337       0: ipp
338       1: pp
339    
340    "No match" is output only if the first match attempt fails.
341    
342    If any of \C, \G, or \L are present in a data line that is successfully
343    matched, the substrings extracted by the convenience functions are output with
344    C, G, or L after the string number instead of a colon. This is in addition to
345    the normal full list. The string length (that is, the return from the
346    extraction function) is given in parentheses after each string for \C and \G.
347    
348  Note that while patterns can be continued over several lines (a plain ">"  Note that while patterns can be continued over several lines (a plain ">"
349  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
350  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 356  following flags has any effect in this c
356  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
357  regular expression: the internal form is output after compilation.  regular expression: the internal form is output after compilation.
358    
359  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
360  after compiling an expression, and outputs the information it gets back. If the  regular expression: information about the compiled pattern is given after
361  pattern is studied, the results of that are also output.  compilation.
362    
363  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
364  pattern after it has been compiled.  pattern after it has been compiled. It is equivalent to adding /M to each
365    regular expression. For compatibility with earlier versions of pcretest, -s is
366    a synonym for -m.
367    
368  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
369  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
370  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
371  2000 times and the timing will be distorted.  20000 times and the timing will be distorted. If you want to change the number
372    of repetitions used for timing, edit the definition of LOOPREPEAT at the top of
373    pcretest.c
374    
375    
376    
# Line 216  The perltest program Line 379  The perltest program
379    
380  The perltest program tests Perl's regular expressions; it has the same  The perltest program tests Perl's regular expressions; it has the same
381  specification as pcretest, and so can be given identical input, except that  specification as pcretest, and so can be given identical input, except that
382  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
383    contents of testinput1 and testinput3 meet this condition.
384    
385  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
386  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
387  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
388  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
389  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
390  from the initial identifying banner.  be identical, apart from the initial identifying banner.
391    
392  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,
393  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
394  test additional features of PCRE.  pcretest uses to test some features of PCRE. The first of these files also
395    contains malformed regular expressions, in order to check that PCRE diagnoses
396    them correctly.
397    
398  Philip Hazel <ph10@cam.ac.uk>  Philip Hazel <ph10@cam.ac.uk>
399  October 1997  July 1999

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