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1 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
21 The distribution should contain the following files:
22
23 ChangeLog log of changes to the code
24 Makefile for building PCRE
25 README this file
26 RunTest a shell script for running tests
27 Tech.Notes notes on the encoding
28 pcre.3 man page for the functions
29 pcreposix.3 man page for the POSIX wrapper API
30 deftables.c auxiliary program for building chartables.c
31 maketables.c )
32 study.c ) source of
33 pcre.c ) the functions
34 pcreposix.c )
35 pcre.h header for the external API
36 pcreposix.h header for the external POSIX wrapper API
37 internal.h header for internal use
38 pcretest.c test program
39 pgrep.1 man page for pgrep
40 pgrep.c source of a grep utility that uses PCRE
41 perltest Perl test program
42 testinput test data, compatible with Perl 5.004 and 5.005
43 testinput2 test data for error messages and non-Perl things
44 testinput3 test data, compatible with Perl 5.005
45 testinput4 test data for locale-specific tests
46 testoutput test results corresponding to testinput
47 testoutput2 test results corresponding to testinput2
48 testoutput3 test results corresponding to testinput3
49 testoutput4 test results corresponding to testinput4
50
51 To build PCRE, edit Makefile for your system (it is a fairly simple make file,
52 and there are some comments at the top) and then run it. It builds two
53 libraries called libpcre.a and libpcreposix.a, a test program called pcretest,
54 and the pgrep command.
55
56 To test PCRE, run the RunTest script in the pcre directory. This runs pcretest
57 on each of the testinput files in turn, and compares the output with the
58 contents of the corresponding testoutput file. A file called testtry is used to
59 hold the output from pcretest (which is documented below).
60
61 To run pcretest on just one of the test files, give its number as an argument
62 to RunTest, for example:
63
64 RunTest 3
65
66 The first and third test files can also be fed directly into the perltest
67 program to check that Perl gives the same results. The third file requires the
68 additional features of release 5.005, which is why it is kept separate from the
69 main test input, which needs only Perl 5.004. In the long run, when 5.005 is
70 widespread, these two test files may get amalgamated.
71
72 The second set of tests check pcre_info(), pcre_study(), error detection and
73 run-time flags that are specific to PCRE, as well as the POSIX wrapper API.
74
75 The fourth set of tests checks pcre_maketables(), the facility for building a
76 set of character tables for a specific locale and using them instead of the
77 default tables. The tests make use of the "fr" (French) locale. Before running
78 the test, the script checks for the presence of this locale by running the
79 "locale" command. If that command fails, or if it doesn't include "fr" in the
80 list of available locales, the fourth test cannot be run, and a comment is
81 output to say why. If running this test produces instances of the error
82
83 ** Failed to set locale "fr"
84
85 in the comparison output, it means that locale is not available on your system,
86 despite being listed by "locale". This does not mean that PCRE is broken.
87
88 To install PCRE, copy libpcre.a to any suitable library directory (e.g.
89 /usr/local/lib), pcre.h to any suitable include directory (e.g.
90 /usr/local/include), and pcre.3 to any suitable man directory (e.g.
91 /usr/local/man/man3).
92
93 To install the pgrep command, copy it to any suitable binary directory, (e.g.
94 /usr/local/bin) and pgrep.1 to any suitable man directory (e.g.
95 /usr/local/man/man1).
96
97 PCRE has its own native API, but a set of "wrapper" functions that are based on
98 the POSIX API are also supplied in the library libpcreposix.a. Note that this
99 just provides a POSIX calling interface to PCRE: the regular expressions
100 themselves still follow Perl syntax and semantics. The header file
101 for the POSIX-style functions is called pcreposix.h. The official POSIX name is
102 regex.h, but I didn't want to risk possible problems with existing files of
103 that name by distributing it that way. To use it with an existing program that
104 uses the POSIX API, it will have to be renamed or pointed at by a link.
105
106
107 Character tables
108 ----------------
109
110 PCRE uses four tables for manipulating and identifying characters. The final
111 argument of the pcre_compile() function is a pointer to a block of memory
112 containing the concatenated tables. A call to pcre_maketables() is used to
113 generate a set of tables in the current locale. However, if the final argument
114 is passed as NULL, a set of default tables that is built into the binary is
115 used.
116
117 The source file called chartables.c contains the default set of tables. This is
118 not supplied in the distribution, but is built by the program deftables
119 (compiled from deftables.c), which uses the ANSI C character handling functions
120 such as isalnum(), isalpha(), isupper(), islower(), etc. to build the table
121 sources. This means that the default C locale set your system will control the
122 contents of the tables. You can change the default tables by editing
123 chartables.c and then re-building PCRE. If you do this, you should probably
124 also edit Makefile to ensure that the file doesn't ever get re-generated.
125
126 The first two 256-byte tables provide lower casing and case flipping functions,
127 respectively. The next table consists of three 32-byte bit maps which identify
128 digits, "word" characters, and white space, respectively. These are used when
129 building 32-byte bit maps that represent character classes.
130
131 The final 256-byte table has bits indicating various character types, as
132 follows:
133
134 1 white space character
135 2 letter
136 4 decimal digit
137 8 hexadecimal digit
138 16 alphanumeric or '_'
139 128 regular expression metacharacter or binary zero
140
141 You should not alter the set of characters that contain the 128 bit, as that
142 will cause PCRE to malfunction.
143
144
145 The pcretest program
146 --------------------
147
148 This program is intended for testing PCRE, but it can also be used for
149 experimenting with regular expressions.
150
151 If it is given two filename arguments, it reads from the first and writes to
152 the second. If it is given only one filename argument, it reads from that file
153 and writes to stdout. Otherwise, it reads from stdin and writes to stdout, and
154 prompts for each line of input.
155
156 The program handles any number of sets of input on a single input file. Each
157 set starts with a regular expression, and continues with any number of data
158 lines to be matched against the pattern. An empty line signals the end of the
159 set. The regular expressions are given enclosed in any non-alphameric
160 delimiters, for example
161
162 /(a|bc)x+yz/
163
164 and may be followed by i, m, s, or x to set the PCRE_CASELESS, PCRE_MULTILINE,
165 PCRE_DOTALL, or PCRE_EXTENDED options, respectively. These options have the
166 same effect as they do in Perl.
167
168 There are also some upper case options that do not match Perl options: /A, /E,
169 and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.
170
171 The /L option must be followed directly by the name of a locale, for example,
172
173 /pattern/Lfr
174
175 For this reason, it must be the last option letter. The given locale is set,
176 pcre_maketables() is called to build a set of character tables for the locale,
177 and this is then passed to pcre_compile() when compiling the regular
178 expression. Without an /L option, NULL is passed as the tables pointer; that
179 is, /L applies only to the expression on which it appears.
180
181 The /I option requests that pcretest output information about the compiled
182 expression (whether it is anchored, has a fixed first character, and so on). It
183 does this by calling pcre_info() after compiling an expression, and outputting
184 the information it gets back. If the pattern is studied, the results of that
185 are also output.
186
187 The /D option is a PCRE debugging feature, which also assumes /I. It causes the
188 internal form of compiled regular expressions to be output after compilation.
189
190 The /S option causes pcre_study() to be called after the expression has been
191 compiled, and the results used when the expression is matched.
192
193 Finally, the /P option causes pcretest to call PCRE via the POSIX wrapper API
194 rather than its native API. When this is done, all other options except /i and
195 /m are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is set if /m
196 is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always, and
197 PCRE_DOTALL unless REG_NEWLINE is set.
198
199 A regular expression can extend over several lines of input; the newlines are
200 included in it. See the testinput files for many examples.
201
202 Before each data line is passed to pcre_exec(), leading and trailing whitespace
203 is removed, and it is then scanned for \ escapes. The following are recognized:
204
205 \a alarm (= BEL)
206 \b backspace
207 \e escape
208 \f formfeed
209 \n newline
210 \r carriage return
211 \t tab
212 \v vertical tab
213 \nnn octal character (up to 3 octal digits)
214 \xhh hexadecimal character (up to 2 hex digits)
215
216 \A pass the PCRE_ANCHORED option to pcre_exec()
217 \B pass the PCRE_NOTBOL option to pcre_exec()
218 \Odd set the size of the output vector passed to pcre_exec() to dd
219 (any number of decimal digits)
220 \Z pass the PCRE_NOTEOL option to pcre_exec()
221
222 A backslash followed by anything else just escapes the anything else. If the
223 very last character is a backslash, it is ignored. This gives a way of passing
224 an empty line as data, since a real empty line terminates the data input.
225
226 If /P was present on the regex, causing the POSIX wrapper API to be used, only
227 \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to
228 regexec() respectively.
229
230 When a match succeeds, pcretest outputs the list of identified substrings that
231 pcre_exec() returns, starting with number 0 for the string that matched the
232 whole pattern. Here is an example of an interactive pcretest run.
233
234 $ pcretest
235 Testing Perl-Compatible Regular Expressions
236 PCRE version 0.90 08-Sep-1997
237
238 re> /^abc(\d+)/
239 data> abc123
240 0: abc123
241 1: 123
242 data> xyz
243 No match
244
245 Note that while patterns can be continued over several lines (a plain ">"
246 prompt is used for continuations), data lines may not. However newlines can be
247 included in data by means of the \n escape.
248
249 If the -p option is given to pcretest, it is equivalent to adding /P to each
250 regular expression: the POSIX wrapper API is used to call PCRE. None of the
251 following flags has any effect in this case.
252
253 If the option -d is given to pcretest, it is equivalent to adding /D to each
254 regular expression: the internal form is output after compilation.
255
256 If the option -i is given to pcretest, it is equivalent to adding /I to each
257 regular expression: information about the compiled pattern is given after
258 compilation.
259
260 If the option -s is given to pcretest, it outputs the size of each compiled
261 pattern after it has been compiled.
262
263 If the -t option is given, each compile, study, and match is run 10000 times
264 while being timed, and the resulting time per compile or match is output in
265 milliseconds. Do not set -t with -s, because you will then get the size output
266 10000 times and the timing will be distorted. If you want to change the number
267 of repetitions used for timing, edit the definition of LOOPREPEAT at the top of
268 pcretest.c
269
270
271
272 The perltest program
273 --------------------
274
275 The perltest program tests Perl's regular expressions; it has the same
276 specification as pcretest, and so can be given identical input, except that
277 input patterns can be followed only by Perl's lower case options. The contents
278 of testinput and testinput3 meet this condition.
279
280 The data lines are processed as Perl strings, so if they contain $ or @
281 characters, these have to be escaped. For this reason, all such characters in
282 the testinput file are escaped so that it can be used for perltest as well as
283 for pcretest, and the special upper case options such as /A that pcretest
284 recognizes are not used in this file. The output should be identical, apart
285 from the initial identifying banner.
286
287 The testinput2 and testinput4 files are not suitable for feeding to Perltest,
288 since they do make use of the special upper case options and escapes that
289 pcretest uses to test some features of PCRE. The first of these files also
290 contains malformed regular expressions, in order to check that PCRE diagnoses
291 them correctly.
292
293 Philip Hazel <ph10@cam.ac.uk>
294 October 1998

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