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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 23 *******************************************************************************
20    
21 nigel 3 The distribution should contain the following files:
22    
23     ChangeLog log of changes to the code
24 nigel 29 LICENCE conditions for the use of PCRE
25 nigel 3 Makefile for building PCRE
26     README this file
27 nigel 23 RunTest a shell script for running tests
28 nigel 3 Tech.Notes notes on the encoding
29     pcre.3 man page for the functions
30     pcreposix.3 man page for the POSIX wrapper API
31 nigel 27 dftables.c auxiliary program for building chartables.c
32 nigel 29 get.c )
33 nigel 25 maketables.c )
34 nigel 3 study.c ) source of
35     pcre.c ) the functions
36     pcreposix.c )
37     pcre.h header for the external API
38     pcreposix.h header for the external POSIX wrapper API
39     internal.h header for internal use
40     pcretest.c test program
41     pgrep.1 man page for pgrep
42     pgrep.c source of a grep utility that uses PCRE
43     perltest Perl test program
44 nigel 23 testinput test data, compatible with Perl 5.004 and 5.005
45 nigel 3 testinput2 test data for error messages and non-Perl things
46 nigel 23 testinput3 test data, compatible with Perl 5.005
47 nigel 25 testinput4 test data for locale-specific tests
48 nigel 3 testoutput test results corresponding to testinput
49     testoutput2 test results corresponding to testinput2
50 nigel 25 testoutput3 test results corresponding to testinput3
51     testoutput4 test results corresponding to testinput4
52 nigel 3
53 nigel 23 To build PCRE, edit Makefile for your system (it is a fairly simple make file,
54     and there are some comments at the top) and then run it. It builds two
55     libraries called libpcre.a and libpcreposix.a, a test program called pcretest,
56     and the pgrep command.
57 nigel 3
58 nigel 23 To test PCRE, run the RunTest script in the pcre directory. This runs pcretest
59     on each of the testinput files in turn, and compares the output with the
60     contents of the corresponding testoutput file. A file called testtry is used to
61     hold the output from pcretest (which is documented below).
62 nigel 3
63 nigel 23 To run pcretest on just one of the test files, give its number as an argument
64     to RunTest, for example:
65 nigel 3
66 nigel 23 RunTest 3
67 nigel 3
68 nigel 23 The first and third test files can also be fed directly into the perltest
69     program to check that Perl gives the same results. The third file requires the
70     additional features of release 5.005, which is why it is kept separate from the
71     main test input, which needs only Perl 5.004. In the long run, when 5.005 is
72     widespread, these two test files may get amalgamated.
73 nigel 3
74 nigel 29 The second set of tests check pcre_info(), pcre_study(), pcre_copy_substring(),
75     pcre_get_substring(), pcre_get_substring_list(), error detection and run-time
76     flags that are specific to PCRE, as well as the POSIX wrapper API.
77 nigel 7
78 nigel 25 The fourth set of tests checks pcre_maketables(), the facility for building a
79     set of character tables for a specific locale and using them instead of the
80     default tables. The tests make use of the "fr" (French) locale. Before running
81     the test, the script checks for the presence of this locale by running the
82     "locale" command. If that command fails, or if it doesn't include "fr" in the
83     list of available locales, the fourth test cannot be run, and a comment is
84     output to say why. If running this test produces instances of the error
85    
86     ** Failed to set locale "fr"
87    
88     in the comparison output, it means that locale is not available on your system,
89     despite being listed by "locale". This does not mean that PCRE is broken.
90    
91 nigel 3 To install PCRE, copy libpcre.a to any suitable library directory (e.g.
92     /usr/local/lib), pcre.h to any suitable include directory (e.g.
93     /usr/local/include), and pcre.3 to any suitable man directory (e.g.
94     /usr/local/man/man3).
95    
96     To install the pgrep command, copy it to any suitable binary directory, (e.g.
97     /usr/local/bin) and pgrep.1 to any suitable man directory (e.g.
98     /usr/local/man/man1).
99    
100     PCRE has its own native API, but a set of "wrapper" functions that are based on
101     the POSIX API are also supplied in the library libpcreposix.a. Note that this
102     just provides a POSIX calling interface to PCRE: the regular expressions
103     themselves still follow Perl syntax and semantics. The header file
104     for the POSIX-style functions is called pcreposix.h. The official POSIX name is
105     regex.h, but I didn't want to risk possible problems with existing files of
106     that name by distributing it that way. To use it with an existing program that
107 nigel 23 uses the POSIX API, it will have to be renamed or pointed at by a link.
108 nigel 3
109    
110     Character tables
111     ----------------
112    
113 nigel 25 PCRE uses four tables for manipulating and identifying characters. The final
114     argument of the pcre_compile() function is a pointer to a block of memory
115     containing the concatenated tables. A call to pcre_maketables() is used to
116     generate a set of tables in the current locale. However, if the final argument
117     is passed as NULL, a set of default tables that is built into the binary is
118     used.
119 nigel 3
120 nigel 25 The source file called chartables.c contains the default set of tables. This is
121 nigel 27 not supplied in the distribution, but is built by the program dftables
122     (compiled from dftables.c), which uses the ANSI C character handling functions
123 nigel 25 such as isalnum(), isalpha(), isupper(), islower(), etc. to build the table
124     sources. This means that the default C locale set your system will control the
125     contents of the tables. You can change the default tables by editing
126     chartables.c and then re-building PCRE. If you do this, you should probably
127     also edit Makefile to ensure that the file doesn't ever get re-generated.
128 nigel 3
129 nigel 25 The first two 256-byte tables provide lower casing and case flipping functions,
130     respectively. The next table consists of three 32-byte bit maps which identify
131     digits, "word" characters, and white space, respectively. These are used when
132     building 32-byte bit maps that represent character classes.
133    
134     The final 256-byte table has bits indicating various character types, as
135 nigel 3 follows:
136    
137     1 white space character
138     2 letter
139     4 decimal digit
140     8 hexadecimal digit
141     16 alphanumeric or '_'
142     128 regular expression metacharacter or binary zero
143    
144     You should not alter the set of characters that contain the 128 bit, as that
145     will cause PCRE to malfunction.
146    
147    
148     The pcretest program
149     --------------------
150    
151     This program is intended for testing PCRE, but it can also be used for
152     experimenting with regular expressions.
153    
154     If it is given two filename arguments, it reads from the first and writes to
155     the second. If it is given only one filename argument, it reads from that file
156     and writes to stdout. Otherwise, it reads from stdin and writes to stdout, and
157     prompts for each line of input.
158    
159     The program handles any number of sets of input on a single input file. Each
160     set starts with a regular expression, and continues with any number of data
161     lines to be matched against the pattern. An empty line signals the end of the
162     set. The regular expressions are given enclosed in any non-alphameric
163 nigel 29 delimiters other than backslash, for example
164 nigel 3
165     /(a|bc)x+yz/
166    
167 nigel 29 White space before the initial delimiter is ignored. A regular expression may
168     be continued over several input lines, in which case the newline characters are
169     included within it. See the testinput files for many examples. It is possible
170     to include the delimiter within the pattern by escaping it, for example
171 nigel 3
172 nigel 29 /abc\/def/
173    
174     If you do so, the escape and the delimiter form part of the pattern, but since
175     delimiters are always non-alphameric, this does not affect its interpretation.
176     If the terminating delimiter is immediately followed by a backslash, for
177     example,
178    
179     /abc/\
180    
181     then a backslash is added to the end of the pattern. This provides a way of
182     testing the error condition that arises if a pattern finishes with a backslash,
183     because
184    
185     /abc\/
186    
187     is interpreted as the first line of a pattern that starts with "abc/", causing
188     pcretest to read the next line as a continuation of the regular expression.
189    
190     The pattern may be followed by i, m, s, or x to set the PCRE_CASELESS,
191     PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. These
192     options have the same effect as they do in Perl.
193    
194 nigel 3 There are also some upper case options that do not match Perl options: /A, /E,
195     and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.
196    
197 nigel 25 The /L option must be followed directly by the name of a locale, for example,
198    
199     /pattern/Lfr
200    
201     For this reason, it must be the last option letter. The given locale is set,
202     pcre_maketables() is called to build a set of character tables for the locale,
203     and this is then passed to pcre_compile() when compiling the regular
204     expression. Without an /L option, NULL is passed as the tables pointer; that
205     is, /L applies only to the expression on which it appears.
206    
207     The /I option requests that pcretest output information about the compiled
208     expression (whether it is anchored, has a fixed first character, and so on). It
209     does this by calling pcre_info() after compiling an expression, and outputting
210     the information it gets back. If the pattern is studied, the results of that
211     are also output.
212    
213     The /D option is a PCRE debugging feature, which also assumes /I. It causes the
214     internal form of compiled regular expressions to be output after compilation.
215    
216     The /S option causes pcre_study() to be called after the expression has been
217     compiled, and the results used when the expression is matched.
218    
219 nigel 3 Finally, the /P option causes pcretest to call PCRE via the POSIX wrapper API
220     rather than its native API. When this is done, all other options except /i and
221     /m are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is set if /m
222     is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always, and
223     PCRE_DOTALL unless REG_NEWLINE is set.
224    
225     Before each data line is passed to pcre_exec(), leading and trailing whitespace
226     is removed, and it is then scanned for \ escapes. The following are recognized:
227    
228     \a alarm (= BEL)
229     \b backspace
230     \e escape
231     \f formfeed
232     \n newline
233     \r carriage return
234     \t tab
235     \v vertical tab
236     \nnn octal character (up to 3 octal digits)
237     \xhh hexadecimal character (up to 2 hex digits)
238    
239     \A pass the PCRE_ANCHORED option to pcre_exec()
240     \B pass the PCRE_NOTBOL option to pcre_exec()
241 nigel 29 \Cdd call pcre_copy_substring() for substring dd after a successful match
242     (any decimal number less than 32)
243     \Gdd call pcre_get_substring() for substring dd after a successful match
244     (any decimal number less than 32)
245     \L call pcre_get_substringlist() after a successful match
246 nigel 3 \Odd set the size of the output vector passed to pcre_exec() to dd
247     (any number of decimal digits)
248     \Z pass the PCRE_NOTEOL option to pcre_exec()
249    
250     A backslash followed by anything else just escapes the anything else. If the
251     very last character is a backslash, it is ignored. This gives a way of passing
252     an empty line as data, since a real empty line terminates the data input.
253    
254     If /P was present on the regex, causing the POSIX wrapper API to be used, only
255     \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to
256     regexec() respectively.
257    
258 nigel 29 When a match succeeds, pcretest outputs the list of captured substrings that
259 nigel 3 pcre_exec() returns, starting with number 0 for the string that matched the
260     whole pattern. Here is an example of an interactive pcretest run.
261    
262     $ pcretest
263     Testing Perl-Compatible Regular Expressions
264     PCRE version 0.90 08-Sep-1997
265    
266 nigel 23 re> /^abc(\d+)/
267     data> abc123
268     0: abc123
269     1: 123
270     data> xyz
271 nigel 3 No match
272    
273 nigel 29 If any of \C, \G, or \L are present in a data line that is successfully
274     matched, the substrings extracted by the convenience functions are output with
275     C, G, or L after the string number instead of a colon. This is in addition to
276     the normal full list. The string length (that is, the return from the
277     extraction function) is given in parentheses after each string for \C and \G.
278    
279 nigel 3 Note that while patterns can be continued over several lines (a plain ">"
280     prompt is used for continuations), data lines may not. However newlines can be
281     included in data by means of the \n escape.
282    
283     If the -p option is given to pcretest, it is equivalent to adding /P to each
284     regular expression: the POSIX wrapper API is used to call PCRE. None of the
285     following flags has any effect in this case.
286    
287     If the option -d is given to pcretest, it is equivalent to adding /D to each
288     regular expression: the internal form is output after compilation.
289    
290 nigel 25 If the option -i is given to pcretest, it is equivalent to adding /I to each
291     regular expression: information about the compiled pattern is given after
292     compilation.
293 nigel 3
294     If the option -s is given to pcretest, it outputs the size of each compiled
295     pattern after it has been compiled.
296    
297 nigel 29 If the -t option is given, each compile, study, and match is run 20000 times
298 nigel 3 while being timed, and the resulting time per compile or match is output in
299     milliseconds. Do not set -t with -s, because you will then get the size output
300 nigel 29 20000 times and the timing will be distorted. If you want to change the number
301 nigel 23 of repetitions used for timing, edit the definition of LOOPREPEAT at the top of
302     pcretest.c
303 nigel 3
304    
305    
306     The perltest program
307     --------------------
308    
309     The perltest program tests Perl's regular expressions; it has the same
310     specification as pcretest, and so can be given identical input, except that
311 nigel 23 input patterns can be followed only by Perl's lower case options. The contents
312     of testinput and testinput3 meet this condition.
313 nigel 3
314     The data lines are processed as Perl strings, so if they contain $ or @
315     characters, these have to be escaped. For this reason, all such characters in
316     the testinput file are escaped so that it can be used for perltest as well as
317     for pcretest, and the special upper case options such as /A that pcretest
318     recognizes are not used in this file. The output should be identical, apart
319     from the initial identifying banner.
320    
321 nigel 25 The testinput2 and testinput4 files are not suitable for feeding to Perltest,
322     since they do make use of the special upper case options and escapes that
323     pcretest uses to test some features of PCRE. The first of these files also
324     contains malformed regular expressions, in order to check that PCRE diagnoses
325     them correctly.
326 nigel 3
327     Philip Hazel <ph10@cam.ac.uk>
328 nigel 29 February 1999

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