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Load pcre-1.00 into code/trunk.
1 README file for PCRE (Perl-compatible regular expressions)
2 ----------------------------------------------------------
4 The distribution should contain the following files:
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
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.
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:
36 pcretest testinput /tmp/anything
37 diff /tmp/anything testoutput
39 Do the same with testinput2, comparing the output with testoutput2, but this
40 time using the -i flag for pcretest, i.e.
42 pcretest -i testinput2 /tmp/anything
43 diff /tmp/anything testoutput2
45 There are two sets of tests because the first set can also be fed directly into
46 the perltest program to check that Perl gives the same results. The second set
47 of tests check pcre_info(), pcre_study(), error detection and run-time flags
48 that are specific to PCRE, as well as the POSIX wrapper API.
50 To install PCRE, copy libpcre.a to any suitable library directory (e.g.
51 /usr/local/lib), pcre.h to any suitable include directory (e.g.
52 /usr/local/include), and pcre.3 to any suitable man directory (e.g.
53 /usr/local/man/man3).
55 To install the pgrep command, copy it to any suitable binary directory, (e.g.
56 /usr/local/bin) and pgrep.1 to any suitable man directory (e.g.
57 /usr/local/man/man1).
59 PCRE has its own native API, but a set of "wrapper" functions that are based on
60 the POSIX API are also supplied in the library libpcreposix.a. Note that this
61 just provides a POSIX calling interface to PCRE: the regular expressions
62 themselves still follow Perl syntax and semantics. The header file
63 for the POSIX-style functions is called pcreposix.h. The official POSIX name is
64 regex.h, but I didn't want to risk possible problems with existing files of
65 that name by distributing it that way. To use it with an existing program that
66 uses the POSIX API it will have to be renamed or pointed at by a link.
69 Character tables
70 ----------------
72 PCRE uses four tables for manipulating and identifying characters. These are
73 compiled from a source file called chartables.c. This is not supplied in
74 the distribution, but is built by the program maketables (compiled from
75 maketables.c), which uses the ANSI C character handling functions such as
76 isalnum(), isalpha(), isupper(), islower(), etc. to build the table sources.
77 This means that the default C locale set in your system may affect the contents
78 of the tables. You can change the tables by editing chartables.c and then
79 re-building PCRE. If you do this, you should probably also edit Makefile to
80 ensure that the file doesn't ever get re-generated.
82 The first two tables pcre_lcc[] and pcre_fcc[] provide lower casing and a
83 case flipping functions, respectively. The pcre_cbits[] table consists of four
84 32-byte bit maps which identify digits, letters, "word" characters, and white
85 space, respectively. These are used when building 32-byte bit maps that
86 represent character classes.
88 The pcre_ctypes[] table has bits indicating various character types, as
89 follows:
91 1 white space character
92 2 letter
93 4 decimal digit
94 8 hexadecimal digit
95 16 alphanumeric or '_'
96 128 regular expression metacharacter or binary zero
98 You should not alter the set of characters that contain the 128 bit, as that
99 will cause PCRE to malfunction.
102 The pcretest program
103 --------------------
105 This program is intended for testing PCRE, but it can also be used for
106 experimenting with regular expressions.
108 If it is given two filename arguments, it reads from the first and writes to
109 the second. If it is given only one filename argument, it reads from that file
110 and writes to stdout. Otherwise, it reads from stdin and writes to stdout, and
111 prompts for each line of input.
113 The program handles any number of sets of input on a single input file. Each
114 set starts with a regular expression, and continues with any number of data
115 lines to be matched against the pattern. An empty line signals the end of the
116 set. The regular expressions are given enclosed in any non-alphameric
117 delimiters, for example
119 /(a|bc)x+yz/
121 and may be followed by i, m, s, or x to set the PCRE_CASELESS, PCRE_MULTILINE,
122 PCRE_DOTALL, or PCRE_EXTENDED options, respectively. These options have the
123 same effect as they do in Perl.
125 There are also some upper case options that do not match Perl options: /A, /E,
126 and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.
127 The /D option is a PCRE debugging feature. It causes the internal form of
128 compiled regular expressions to be output after compilation. The /S option
129 causes pcre_study() to be called after the expression has been compiled, and
130 the results used when the expression is matched. If /I is present as well as
131 /S, then pcre_study() is called with the PCRE_CASELESS option.
133 Finally, the /P option causes pcretest to call PCRE via the POSIX wrapper API
134 rather than its native API. When this is done, all other options except /i and
135 /m are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is set if /m
136 is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always, and
137 PCRE_DOTALL unless REG_NEWLINE is set.
139 A regular expression can extend over several lines of input; the newlines are
140 included in it. See the testinput file for many examples.
142 Before each data line is passed to pcre_exec(), leading and trailing whitespace
143 is removed, and it is then scanned for \ escapes. The following are recognized:
145 \a alarm (= BEL)
146 \b backspace
147 \e escape
148 \f formfeed
149 \n newline
150 \r carriage return
151 \t tab
152 \v vertical tab
153 \nnn octal character (up to 3 octal digits)
154 \xhh hexadecimal character (up to 2 hex digits)
156 \A pass the PCRE_ANCHORED option to pcre_exec()
157 \B pass the PCRE_NOTBOL option to pcre_exec()
158 \E pass the PCRE_DOLLAR_ENDONLY option to pcre_exec()
159 \I pass the PCRE_CASELESS option to pcre_exec()
160 \M pass the PCRE_MULTILINE option to pcre_exec()
161 \S pass the PCRE_DOTALL option to pcre_exec()
162 \Odd set the size of the output vector passed to pcre_exec() to dd
163 (any number of decimal digits)
164 \Z pass the PCRE_NOTEOL option to pcre_exec()
166 A backslash followed by anything else just escapes the anything else. If the
167 very last character is a backslash, it is ignored. This gives a way of passing
168 an empty line as data, since a real empty line terminates the data input.
170 If /P was present on the regex, causing the POSIX wrapper API to be used, only
171 \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to
172 regexec() respectively.
174 When a match succeeds, pcretest outputs the list of identified substrings that
175 pcre_exec() returns, starting with number 0 for the string that matched the
176 whole pattern. Here is an example of an interactive pcretest run.
178 $ pcretest
179 Testing Perl-Compatible Regular Expressions
180 PCRE version 0.90 08-Sep-1997
182 re> /^abc(\d+)/
183 data> abc123
184 0: abc123
185 1: 123
186 data> xyz
187 No match
189 Note that while patterns can be continued over several lines (a plain ">"
190 prompt is used for continuations), data lines may not. However newlines can be
191 included in data by means of the \n escape.
193 If the -p option is given to pcretest, it is equivalent to adding /P to each
194 regular expression: the POSIX wrapper API is used to call PCRE. None of the
195 following flags has any effect in this case.
197 If the option -d is given to pcretest, it is equivalent to adding /D to each
198 regular expression: the internal form is output after compilation.
200 If the option -i (for "information") is given to pcretest, it calls pcre_info()
201 after compiling an expression, and outputs the information it gets back. If the
202 pattern is studied, the results of that are also output.
204 If the option -s is given to pcretest, it outputs the size of each compiled
205 pattern after it has been compiled.
207 If the -t option is given, each compile, study, and match is run 2000 times
208 while being timed, and the resulting time per compile or match is output in
209 milliseconds. Do not set -t with -s, because you will then get the size output
210 2000 times and the timing will be distorted.
214 The perltest program
215 --------------------
217 The perltest program tests Perl's regular expressions; it has the same
218 specification as pcretest, and so can be given identical input, except that
219 input patterns can be followed only by Perl's lower case options.
221 The data lines are processed as Perl strings, so if they contain $ or @
222 characters, these have to be escaped. For this reason, all such characters in
223 the testinput file are escaped so that it can be used for perltest as well as
224 for pcretest, and the special upper case options such as /A that pcretest
225 recognizes are not used in this file. The output should be identical, apart
226 from the initial identifying banner.
228 The testinput2 file is not suitable for feeding to Perltest, since it does
229 make use of the special upper case options and escapes that pcretest uses to
230 test additional features of PCRE.
232 Philip Hazel <ph10@cam.ac.uk>
233 October 1997

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