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Tag code/trunk as code/tags/pcre-2.00.

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
13 The distribution should contain the following files:
14
15 ChangeLog log of changes to the code
16 Makefile for building PCRE
17 README this file
18 RunTest a shell script for running tests
19 Tech.Notes notes on the encoding
20 pcre.3 man page for the functions
21 pcreposix.3 man page for the POSIX wrapper API
22 maketables.c auxiliary program for building chartables.c
23 study.c ) source of
24 pcre.c ) the functions
25 pcreposix.c )
26 pcre.h header for the external API
27 pcreposix.h header for the external POSIX wrapper API
28 internal.h header for internal use
29 pcretest.c test program
30 pgrep.1 man page for pgrep
31 pgrep.c source of a grep utility that uses PCRE
32 perltest Perl test program
33 testinput test data, compatible with Perl 5.004 and 5.005
34 testinput2 test data for error messages and non-Perl things
35 testinput3 test data, compatible with Perl 5.005
36 testoutput test results corresponding to testinput
37 testoutput2 test results corresponding to testinput2
38 testoutput3 test results corresponding to testinpug3
39
40 To build PCRE, edit Makefile for your system (it is a fairly simple make file,
41 and there are some comments at the top) and then run it. It builds two
42 libraries called libpcre.a and libpcreposix.a, a test program called pcretest,
43 and the pgrep command.
44
45 To test PCRE, run the RunTest script in the pcre directory. This runs pcretest
46 on each of the testinput files in turn, and compares the output with the
47 contents of the corresponding testoutput file. A file called testtry is used to
48 hold the output from pcretest (which is documented below).
49
50 To run pcretest on just one of the test files, give its number as an argument
51 to RunTest, for example:
52
53 RunTest 3
54
55 The first and third test files can also be fed directly into the perltest
56 program to check that Perl gives the same results. The third file requires the
57 additional features of release 5.005, which is why it is kept separate from the
58 main test input, which needs only Perl 5.004. In the long run, when 5.005 is
59 widespread, these two test files may get amalgamated.
60
61 The second set of tests check pcre_info(), pcre_study(), error detection and
62 run-time flags that are specific to PCRE, as well as the POSIX wrapper API.
63
64 To install PCRE, copy libpcre.a to any suitable library directory (e.g.
65 /usr/local/lib), pcre.h to any suitable include directory (e.g.
66 /usr/local/include), and pcre.3 to any suitable man directory (e.g.
67 /usr/local/man/man3).
68
69 To install the pgrep command, copy it to any suitable binary directory, (e.g.
70 /usr/local/bin) and pgrep.1 to any suitable man directory (e.g.
71 /usr/local/man/man1).
72
73 PCRE has its own native API, but a set of "wrapper" functions that are based on
74 the POSIX API are also supplied in the library libpcreposix.a. Note that this
75 just provides a POSIX calling interface to PCRE: the regular expressions
76 themselves still follow Perl syntax and semantics. The header file
77 for the POSIX-style functions is called pcreposix.h. The official POSIX name is
78 regex.h, but I didn't want to risk possible problems with existing files of
79 that name by distributing it that way. To use it with an existing program that
80 uses the POSIX API, it will have to be renamed or pointed at by a link.
81
82
83 Character tables
84 ----------------
85
86 PCRE uses four tables for manipulating and identifying characters. These are
87 compiled from a source file called chartables.c. This is not supplied in
88 the distribution, but is built by the program maketables (compiled from
89 maketables.c), which uses the ANSI C character handling functions such as
90 isalnum(), isalpha(), isupper(), islower(), etc. to build the table sources.
91 This means that the default C locale set in your system may affect the contents
92 of the tables. You can change the tables by editing chartables.c and then
93 re-building PCRE. If you do this, you should probably also edit Makefile to
94 ensure that the file doesn't ever get re-generated.
95
96 The first two tables pcre_lcc[] and pcre_fcc[] provide lower casing and a
97 case flipping functions, respectively. The pcre_cbits[] table consists of four
98 32-byte bit maps which identify digits, letters, "word" characters, and white
99 space, respectively. These are used when building 32-byte bit maps that
100 represent character classes.
101
102 The pcre_ctypes[] table has bits indicating various character types, as
103 follows:
104
105 1 white space character
106 2 letter
107 4 decimal digit
108 8 hexadecimal digit
109 16 alphanumeric or '_'
110 128 regular expression metacharacter or binary zero
111
112 You should not alter the set of characters that contain the 128 bit, as that
113 will cause PCRE to malfunction.
114
115
116 The pcretest program
117 --------------------
118
119 This program is intended for testing PCRE, but it can also be used for
120 experimenting with regular expressions.
121
122 If it is given two filename arguments, it reads from the first and writes to
123 the second. If it is given only one filename argument, it reads from that file
124 and writes to stdout. Otherwise, it reads from stdin and writes to stdout, and
125 prompts for each line of input.
126
127 The program handles any number of sets of input on a single input file. Each
128 set starts with a regular expression, and continues with any number of data
129 lines to be matched against the pattern. An empty line signals the end of the
130 set. The regular expressions are given enclosed in any non-alphameric
131 delimiters, for example
132
133 /(a|bc)x+yz/
134
135 and may be followed by i, m, s, or x to set the PCRE_CASELESS, PCRE_MULTILINE,
136 PCRE_DOTALL, or PCRE_EXTENDED options, respectively. These options have the
137 same effect as they do in Perl.
138
139 There are also some upper case options that do not match Perl options: /A, /E,
140 and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.
141 The /D option is a PCRE debugging feature. It causes the internal form of
142 compiled regular expressions to be output after compilation. The /S option
143 causes pcre_study() to be called after the expression has been compiled, and
144 the results used when the expression is matched.
145
146 Finally, the /P option causes pcretest to call PCRE via the POSIX wrapper API
147 rather than its native API. When this is done, all other options except /i and
148 /m are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is set if /m
149 is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always, and
150 PCRE_DOTALL unless REG_NEWLINE is set.
151
152 A regular expression can extend over several lines of input; the newlines are
153 included in it. See the testinput files for many examples.
154
155 Before each data line is passed to pcre_exec(), leading and trailing whitespace
156 is removed, and it is then scanned for \ escapes. The following are recognized:
157
158 \a alarm (= BEL)
159 \b backspace
160 \e escape
161 \f formfeed
162 \n newline
163 \r carriage return
164 \t tab
165 \v vertical tab
166 \nnn octal character (up to 3 octal digits)
167 \xhh hexadecimal character (up to 2 hex digits)
168
169 \A pass the PCRE_ANCHORED option to pcre_exec()
170 \B pass the PCRE_NOTBOL option to pcre_exec()
171 \Odd set the size of the output vector passed to pcre_exec() to dd
172 (any number of decimal digits)
173 \Z pass the PCRE_NOTEOL option to pcre_exec()
174
175 A backslash followed by anything else just escapes the anything else. If the
176 very last character is a backslash, it is ignored. This gives a way of passing
177 an empty line as data, since a real empty line terminates the data input.
178
179 If /P was present on the regex, causing the POSIX wrapper API to be used, only
180 \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to
181 regexec() respectively.
182
183 When a match succeeds, pcretest outputs the list of identified substrings that
184 pcre_exec() returns, starting with number 0 for the string that matched the
185 whole pattern. Here is an example of an interactive pcretest run.
186
187 $ pcretest
188 Testing Perl-Compatible Regular Expressions
189 PCRE version 0.90 08-Sep-1997
190
191 re> /^abc(\d+)/
192 data> abc123
193 0: abc123
194 1: 123
195 data> xyz
196 No match
197
198 Note that while patterns can be continued over several lines (a plain ">"
199 prompt is used for continuations), data lines may not. However newlines can be
200 included in data by means of the \n escape.
201
202 If the -p option is given to pcretest, it is equivalent to adding /P to each
203 regular expression: the POSIX wrapper API is used to call PCRE. None of the
204 following flags has any effect in this case.
205
206 If the option -d is given to pcretest, it is equivalent to adding /D to each
207 regular expression: the internal form is output after compilation.
208
209 If the option -i (for "information") is given to pcretest, it calls pcre_info()
210 after compiling an expression, and outputs the information it gets back. If the
211 pattern is studied, the results of that are also output.
212
213 If the option -s is given to pcretest, it outputs the size of each compiled
214 pattern after it has been compiled.
215
216 If the -t option is given, each compile, study, and match is run 10000 times
217 while being timed, and the resulting time per compile or match is output in
218 milliseconds. Do not set -t with -s, because you will then get the size output
219 10000 times and the timing will be distorted. If you want to change the number
220 of repetitions used for timing, edit the definition of LOOPREPEAT at the top of
221 pcretest.c
222
223
224
225 The perltest program
226 --------------------
227
228 The perltest program tests Perl's regular expressions; it has the same
229 specification as pcretest, and so can be given identical input, except that
230 input patterns can be followed only by Perl's lower case options. The contents
231 of testinput and testinput3 meet this condition.
232
233 The data lines are processed as Perl strings, so if they contain $ or @
234 characters, these have to be escaped. For this reason, all such characters in
235 the testinput file are escaped so that it can be used for perltest as well as
236 for pcretest, and the special upper case options such as /A that pcretest
237 recognizes are not used in this file. The output should be identical, apart
238 from the initial identifying banner.
239
240 The testinput2 file is not suitable for feeding to Perltest, since it does
241 make use of the special upper case options and escapes that pcretest uses to
242 test some features of PCRE. It also contains malformed regular expressions, in
243 order to check that PCRE diagnoses them correctly.
244
245 Philip Hazel <ph10@cam.ac.uk>
246 September 1998

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