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Tag code/trunk as code/tags/pcre-1.08.

1 README file for PCRE (Perl-compatible regular expressions)
2 ----------------------------------------------------------
3
4 The distribution should contain the following files:
5
6 ChangeLog log of changes to the code
7 Makefile for building PCRE
8 Performance notes on performance
9 README this file
10 Tech.Notes notes on the encoding
11 pcre.3 man page for the functions
12 pcreposix.3 man page for the POSIX wrapper API
13 maketables.c auxiliary program for building chartables.c
14 study.c ) source of
15 pcre.c ) the functions
16 pcreposix.c )
17 pcre.h header for the external API
18 pcreposix.h header for the external POSIX wrapper API
19 internal.h header for internal use
20 pcretest.c test program
21 pgrep.1 man page for pgrep
22 pgrep.c source of a grep utility that uses PCRE
23 perltest Perl test program
24 testinput test data, compatible with Perl
25 testinput2 test data for error messages and non-Perl things
26 testoutput test results corresponding to testinput
27 testoutput2 test results corresponding to testinput2
28
29 To build PCRE, edit Makefile for your system (it is a fairly simple make file)
30 and then run it. It builds a two libraries called libpcre.a and libpcreposix.a,
31 a test program called pcretest, and the pgrep command.
32
33 To test PCRE, run pcretest on the file testinput, and compare the output with
34 the contents of testoutput. There should be no differences. For example:
35
36 pcretest testinput some.file
37 diff some.file testoutput
38
39 Do the same with testinput2, comparing the output with testoutput2, but this
40 time using the -i flag for pcretest, i.e.
41
42 pcretest -i testinput2 some.file
43 diff some.file testoutput2
44
45 The make target "runtest" runs both these tests, using the file "testtry" to
46 store the intermediate output, deleting it at the end if all goes well.
47
48 There are two sets of tests because the first set can also be fed directly into
49 the perltest program to check that Perl gives the same results. The second set
50 of tests check pcre_info(), pcre_study(), error detection and run-time flags
51 that are specific to PCRE, as well as the POSIX wrapper API.
52
53 To install PCRE, copy libpcre.a to any suitable library directory (e.g.
54 /usr/local/lib), pcre.h to any suitable include directory (e.g.
55 /usr/local/include), and pcre.3 to any suitable man directory (e.g.
56 /usr/local/man/man3).
57
58 To install the pgrep command, copy it to any suitable binary directory, (e.g.
59 /usr/local/bin) and pgrep.1 to any suitable man directory (e.g.
60 /usr/local/man/man1).
61
62 PCRE has its own native API, but a set of "wrapper" functions that are based on
63 the POSIX API are also supplied in the library libpcreposix.a. Note that this
64 just provides a POSIX calling interface to PCRE: the regular expressions
65 themselves still follow Perl syntax and semantics. The header file
66 for the POSIX-style functions is called pcreposix.h. The official POSIX name is
67 regex.h, but I didn't want to risk possible problems with existing files of
68 that name by distributing it that way. To use it with an existing program that
69 uses the POSIX API it will have to be renamed or pointed at by a link.
70
71
72 Character tables
73 ----------------
74
75 PCRE uses four tables for manipulating and identifying characters. These are
76 compiled from a source file called chartables.c. This is not supplied in
77 the distribution, but is built by the program maketables (compiled from
78 maketables.c), which uses the ANSI C character handling functions such as
79 isalnum(), isalpha(), isupper(), islower(), etc. to build the table sources.
80 This means that the default C locale set in your system may affect the contents
81 of the tables. You can change the tables by editing chartables.c and then
82 re-building PCRE. If you do this, you should probably also edit Makefile to
83 ensure that the file doesn't ever get re-generated.
84
85 The first two tables pcre_lcc[] and pcre_fcc[] provide lower casing and a
86 case flipping functions, respectively. The pcre_cbits[] table consists of four
87 32-byte bit maps which identify digits, letters, "word" characters, and white
88 space, respectively. These are used when building 32-byte bit maps that
89 represent character classes.
90
91 The pcre_ctypes[] table has bits indicating various character types, as
92 follows:
93
94 1 white space character
95 2 letter
96 4 decimal digit
97 8 hexadecimal digit
98 16 alphanumeric or '_'
99 128 regular expression metacharacter or binary zero
100
101 You should not alter the set of characters that contain the 128 bit, as that
102 will cause PCRE to malfunction.
103
104
105 The pcretest program
106 --------------------
107
108 This program is intended for testing PCRE, but it can also be used for
109 experimenting with regular expressions.
110
111 If it is given two filename arguments, it reads from the first and writes to
112 the second. If it is given only one filename argument, it reads from that file
113 and writes to stdout. Otherwise, it reads from stdin and writes to stdout, and
114 prompts for each line of input.
115
116 The program handles any number of sets of input on a single input file. Each
117 set starts with a regular expression, and continues with any number of data
118 lines to be matched against the pattern. An empty line signals the end of the
119 set. The regular expressions are given enclosed in any non-alphameric
120 delimiters, for example
121
122 /(a|bc)x+yz/
123
124 and may be followed by i, m, s, or x to set the PCRE_CASELESS, PCRE_MULTILINE,
125 PCRE_DOTALL, or PCRE_EXTENDED options, respectively. These options have the
126 same effect as they do in Perl.
127
128 There are also some upper case options that do not match Perl options: /A, /E,
129 and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.
130 The /D option is a PCRE debugging feature. It causes the internal form of
131 compiled regular expressions to be output after compilation. The /S option
132 causes pcre_study() to be called after the expression has been compiled, and
133 the results used when the expression is matched. If /I is present as well as
134 /S, then pcre_study() is called with the PCRE_CASELESS option.
135
136 Finally, the /P option causes pcretest to call PCRE via the POSIX wrapper API
137 rather than its native API. When this is done, all other options except /i and
138 /m are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is set if /m
139 is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always, and
140 PCRE_DOTALL unless REG_NEWLINE is set.
141
142 A regular expression can extend over several lines of input; the newlines are
143 included in it. See the testinput file for many examples.
144
145 Before each data line is passed to pcre_exec(), leading and trailing whitespace
146 is removed, and it is then scanned for \ escapes. The following are recognized:
147
148 \a alarm (= BEL)
149 \b backspace
150 \e escape
151 \f formfeed
152 \n newline
153 \r carriage return
154 \t tab
155 \v vertical tab
156 \nnn octal character (up to 3 octal digits)
157 \xhh hexadecimal character (up to 2 hex digits)
158
159 \A pass the PCRE_ANCHORED option to pcre_exec()
160 \B pass the PCRE_NOTBOL option to pcre_exec()
161 \E pass the PCRE_DOLLAR_ENDONLY option to pcre_exec()
162 \I pass the PCRE_CASELESS option to pcre_exec()
163 \M pass the PCRE_MULTILINE option to pcre_exec()
164 \S pass the PCRE_DOTALL option to pcre_exec()
165 \Odd set the size of the output vector passed to pcre_exec() to dd
166 (any number of decimal digits)
167 \Z pass the PCRE_NOTEOL option to pcre_exec()
168
169 A backslash followed by anything else just escapes the anything else. If the
170 very last character is a backslash, it is ignored. This gives a way of passing
171 an empty line as data, since a real empty line terminates the data input.
172
173 If /P was present on the regex, causing the POSIX wrapper API to be used, only
174 \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to
175 regexec() respectively.
176
177 When a match succeeds, pcretest outputs the list of identified substrings that
178 pcre_exec() returns, starting with number 0 for the string that matched the
179 whole pattern. Here is an example of an interactive pcretest run.
180
181 $ pcretest
182 Testing Perl-Compatible Regular Expressions
183 PCRE version 0.90 08-Sep-1997
184
185 re> /^abc(\d+)/
186 data> abc123
187 0: abc123
188 1: 123
189 data> xyz
190 No match
191
192 Note that while patterns can be continued over several lines (a plain ">"
193 prompt is used for continuations), data lines may not. However newlines can be
194 included in data by means of the \n escape.
195
196 If the -p option is given to pcretest, it is equivalent to adding /P to each
197 regular expression: the POSIX wrapper API is used to call PCRE. None of the
198 following flags has any effect in this case.
199
200 If the option -d is given to pcretest, it is equivalent to adding /D to each
201 regular expression: the internal form is output after compilation.
202
203 If the option -i (for "information") is given to pcretest, it calls pcre_info()
204 after compiling an expression, and outputs the information it gets back. If the
205 pattern is studied, the results of that are also output.
206
207 If the option -s is given to pcretest, it outputs the size of each compiled
208 pattern after it has been compiled.
209
210 If the -t option is given, each compile, study, and match is run 2000 times
211 while being timed, and the resulting time per compile or match is output in
212 milliseconds. Do not set -t with -s, because you will then get the size output
213 2000 times and the timing will be distorted.
214
215
216
217 The perltest program
218 --------------------
219
220 The perltest program tests Perl's regular expressions; it has the same
221 specification as pcretest, and so can be given identical input, except that
222 input patterns can be followed only by Perl's lower case options.
223
224 The data lines are processed as Perl strings, so if they contain $ or @
225 characters, these have to be escaped. For this reason, all such characters in
226 the testinput file are escaped so that it can be used for perltest as well as
227 for pcretest, and the special upper case options such as /A that pcretest
228 recognizes are not used in this file. The output should be identical, apart
229 from the initial identifying banner.
230
231 The testinput2 file is not suitable for feeding to Perltest, since it does
232 make use of the special upper case options and escapes that pcretest uses to
233 test additional features of PCRE.
234
235 Philip Hazel <ph10@cam.ac.uk>
236 October 1997

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