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1 nigel 3 README file for PCRE (Perl-compatible regular expressions)
2     ----------------------------------------------------------
3    
4 nigel 23 *******************************************************************************
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 nigel 25 * *
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 nigel 35 * *
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 nigel 23 *******************************************************************************
34    
35 nigel 35
36 nigel 3 The distribution should contain the following files:
37    
38     ChangeLog log of changes to the code
39 nigel 29 LICENCE conditions for the use of PCRE
40 nigel 37 Makefile for building PCRE in Unix systems
41 nigel 3 README this file
42 nigel 37 RunTest a Unix shell script for running tests
43 nigel 3 Tech.Notes notes on the encoding
44 nigel 37 pcre.3 man page source for the functions
45     pcre.3.txt plain text version
46     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 nigel 27 dftables.c auxiliary program for building chartables.c
51 nigel 29 get.c )
52 nigel 25 maketables.c )
53 nigel 3 study.c ) source of
54     pcre.c ) the functions
55     pcreposix.c )
56     pcre.h header for the external API
57     pcreposix.h header for the external POSIX wrapper API
58     internal.h header for internal use
59     pcretest.c test program
60 nigel 37 pgrep.1 man page source for pgrep
61     pgrep.1.txt plain text version
62     pgrep.1.HTML HTML version
63 nigel 3 pgrep.c source of a grep utility that uses PCRE
64     perltest Perl test program
65 nigel 33 testinput1 test data, compatible with Perl 5.004 and 5.005
66 nigel 3 testinput2 test data for error messages and non-Perl things
67 nigel 23 testinput3 test data, compatible with Perl 5.005
68 nigel 25 testinput4 test data for locale-specific tests
69 nigel 35 testoutput1 test results corresponding to testinput1
70 nigel 3 testoutput2 test results corresponding to testinput2
71 nigel 25 testoutput3 test results corresponding to testinput3
72     testoutput4 test results corresponding to testinput4
73 nigel 39 dll.mk for Win32 DLL
74     pcre.def ditto
75 nigel 3
76 nigel 37 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 nigel 3
85 nigel 37 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 nigel 39 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 nigel 37 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 nigel 23 contents of the corresponding testoutput file. A file called testtry is used to
105 nigel 37 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 nigel 3
108 nigel 23 RunTest 3
109 nigel 3
110 nigel 23 The first and third test files can also be fed directly into the perltest
111 nigel 37 script to check that Perl gives the same results. The third file requires the
112 nigel 23 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 nigel 3
116 nigel 29 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 nigel 7
120 nigel 25 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     in the comparison output, it means that locale is not available on your system,
131     despite being listed by "locale". This does not mean that PCRE is broken.
132    
133 nigel 3 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
135     just provides a POSIX calling interface to PCRE: the regular expressions
136     themselves still follow Perl syntax and semantics. The header file
137     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
139     that name by distributing it that way. To use it with an existing program that
140 nigel 23 uses the POSIX API, it will have to be renamed or pointed at by a link.
141 nigel 3
142    
143     Character tables
144     ----------------
145    
146 nigel 25 PCRE uses four tables for manipulating and identifying characters. The final
147     argument of the pcre_compile() function is a pointer to a block of memory
148 nigel 35 containing the concatenated tables. A call to pcre_maketables() can be used to
149     generate a set of tables in the current locale. If the final argument for
150     pcre_compile() is passed as NULL, a set of default tables that is built into
151     the binary is used.
152 nigel 3
153 nigel 25 The source file called chartables.c contains the default set of tables. This is
154 nigel 27 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 nigel 25 such as isalnum(), isalpha(), isupper(), islower(), etc. to build the table
157 nigel 35 sources. This means that the default C locale which is set for your system will
158     control the contents of these default tables. You can change the default tables
159     by editing chartables.c and then re-building PCRE. If you do this, you should
160     probably also edit Makefile to ensure that the file doesn't ever get
161     re-generated.
162 nigel 3
163 nigel 25 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 final 256-byte table has bits indicating various character types, as
169 nigel 3 follows:
170    
171     1 white space character
172     2 letter
173     4 decimal digit
174     8 hexadecimal digit
175     16 alphanumeric or '_'
176     128 regular expression metacharacter or binary zero
177    
178     You should not alter the set of characters that contain the 128 bit, as that
179     will cause PCRE to malfunction.
180    
181    
182     The pcretest program
183     --------------------
184    
185     This program is intended for testing PCRE, but it can also be used for
186     experimenting with regular expressions.
187    
188     If it is given two filename arguments, it reads from the first and writes to
189     the second. If it is given only one filename argument, it reads from that file
190     and writes to stdout. Otherwise, it reads from stdin and writes to stdout, and
191     prompts for each line of input.
192    
193     The program handles any number of sets of input on a single input file. Each
194     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
196     set. The regular expressions are given enclosed in any non-alphameric
197 nigel 29 delimiters other than backslash, for example
198 nigel 3
199     /(a|bc)x+yz/
200    
201 nigel 29 White space before the initial delimiter is ignored. A regular expression may
202     be continued over several input lines, in which case the newline characters are
203     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 nigel 3
206 nigel 29 /abc\/def/
207    
208     If you do so, the escape and the delimiter form part of the pattern, but since
209     delimiters are always non-alphameric, this does not affect its interpretation.
210     If the terminating delimiter is immediately followed by a backslash, for
211     example,
212    
213     /abc/\
214    
215 nigel 35 then a backslash is added to the end of the pattern. This is done to provide a
216     way of testing the error condition that arises if a pattern finishes with a
217     backslash, because
218 nigel 29
219     /abc\/
220    
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 nigel 35 PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. For
226     example:
227 nigel 29
228 nigel 35 /caseless/i
229 nigel 3
230 nigel 35 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 nigel 25
234 nigel 35 Searching for all possible matches within each subject string can be requested
235 nigel 39 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 nigel 35
243 nigel 39 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 nigel 35 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 nigel 25 /pattern/Lfr
259    
260 nigel 35 For this reason, it must be the last modifier letter. The given locale is set,
261 nigel 25 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 nigel 35 expression. Without an /L modifier, NULL is passed as the tables pointer; that
264 nigel 25 is, /L applies only to the expression on which it appears.
265    
266 nigel 35 The /I modifier requests that pcretest output information about the compiled
267 nigel 25 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 nigel 35 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 nigel 25
276 nigel 35 The /S modifier causes pcre_study() to be called after the expression has been
277 nigel 25 compiled, and the results used when the expression is matched.
278    
279 nigel 37 The /M modifier causes the size of memory block used to hold the compiled
280     pattern to be output.
281 nigel 31
282 nigel 35 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 nigel 3
288     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:
290    
291     \a alarm (= BEL)
292     \b backspace
293     \e escape
294     \f formfeed
295     \n newline
296     \r carriage return
297     \t tab
298     \v vertical tab
299     \nnn octal character (up to 3 octal digits)
300     \xhh hexadecimal character (up to 2 hex digits)
301    
302     \A pass the PCRE_ANCHORED option to pcre_exec()
303     \B pass the PCRE_NOTBOL option to pcre_exec()
304 nigel 29 \Cdd call pcre_copy_substring() for substring dd after a successful match
305     (any decimal number less than 32)
306     \Gdd call pcre_get_substring() for substring dd after a successful match
307     (any decimal number less than 32)
308     \L call pcre_get_substringlist() after a successful match
309 nigel 37 \N pass the PCRE_NOTEMPTY option to pcre_exec()
310 nigel 3 \Odd set the size of the output vector passed to pcre_exec() to dd
311     (any number of decimal digits)
312     \Z pass the PCRE_NOTEOL option to pcre_exec()
313    
314     A backslash followed by anything else just escapes the anything else. If the
315     very last character is a backslash, it is ignored. This gives a way of passing
316     an empty line as data, since a real empty line terminates the data input.
317    
318     If /P was present on the regex, causing the POSIX wrapper API to be used, only
319     \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to
320     regexec() respectively.
321    
322 nigel 29 When a match succeeds, pcretest outputs the list of captured substrings that
323 nigel 3 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.
325    
326     $ pcretest
327 nigel 35 PCRE version 2.06 08-Jun-1999
328 nigel 3
329 nigel 23 re> /^abc(\d+)/
330     data> abc123
331 nigel 35 0: abc123
332     1: 123
333 nigel 23 data> xyz
334 nigel 3 No match
335    
336 nigel 35 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 nigel 29 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 nigel 3 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
367     included in data by means of the \n escape.
368    
369     If the -p option is given to pcretest, it is equivalent to adding /P to each
370     regular expression: the POSIX wrapper API is used to call PCRE. None of the
371     following flags has any effect in this case.
372    
373     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.
375    
376 nigel 25 If the option -i is given to pcretest, it is equivalent to adding /I to each
377     regular expression: information about the compiled pattern is given after
378     compilation.
379 nigel 3
380 nigel 31 If the option -m is given to pcretest, it outputs the size of each compiled
381     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 nigel 3
385 nigel 29 If the -t option is given, each compile, study, and match is run 20000 times
386 nigel 3 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
388 nigel 29 20000 times and the timing will be distorted. If you want to change the number
389 nigel 23 of repetitions used for timing, edit the definition of LOOPREPEAT at the top of
390     pcretest.c
391 nigel 3
392    
393    
394     The perltest program
395     --------------------
396    
397     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
399 nigel 35 input patterns can be followed only by Perl's lower case modifiers. The
400     contents of testinput1 and testinput3 meet this condition.
401 nigel 3
402 nigel 37 The data lines are processed as Perl double-quoted strings, so if they contain
403     " \ $ or @ characters, these have to be escaped. For this reason, all such
404     characters in testinput1 and testinput3 are escaped so that they can be used
405     for perltest as well as for pcretest, and the special upper case modifiers such
406     as /A that pcretest recognizes are not used in these files. The output should
407     be identical, apart from the initial identifying banner.
408 nigel 3
409 nigel 35 The testinput2 and testinput4 files are not suitable for feeding to perltest,
410     since they do make use of the special upper case modifiers and escapes that
411 nigel 25 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 nigel 3
415     Philip Hazel <ph10@cam.ac.uk>
416 nigel 37 July 1999

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