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1 nigel 3 README file for PCRE (Perl-compatible regular expressions)
2     ----------------------------------------------------------
4 nigel 23 *******************************************************************************
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     *******************************************************************************
13 nigel 3 The distribution should contain the following files:
15     ChangeLog log of changes to the code
16     Makefile for building PCRE
17     README this file
18 nigel 23 RunTest a shell script for running tests
19 nigel 3 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 nigel 23 testinput test data, compatible with Perl 5.004 and 5.005
34 nigel 3 testinput2 test data for error messages and non-Perl things
35 nigel 23 testinput3 test data, compatible with Perl 5.005
36 nigel 3 testoutput test results corresponding to testinput
37     testoutput2 test results corresponding to testinput2
38 nigel 23 testoutput3 test results corresponding to testinpug3
39 nigel 3
40 nigel 23 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 nigel 3
45 nigel 23 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 nigel 3
50 nigel 23 To run pcretest on just one of the test files, give its number as an argument
51     to RunTest, for example:
52 nigel 3
53 nigel 23 RunTest 3
54 nigel 3
55 nigel 23 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 nigel 3
61 nigel 23 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 nigel 7
64 nigel 3 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).
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).
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 nigel 23 uses the POSIX API, it will have to be renamed or pointed at by a link.
81 nigel 3
83     Character tables
84     ----------------
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.
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.
102     The pcre_ctypes[] table has bits indicating various character types, as
103     follows:
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
112     You should not alter the set of characters that contain the 128 bit, as that
113     will cause PCRE to malfunction.
116     The pcretest program
117     --------------------
119     This program is intended for testing PCRE, but it can also be used for
120     experimenting with regular expressions.
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.
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
133     /(a|bc)x+yz/
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.
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 nigel 23 the results used when the expression is matched.
145 nigel 3
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.
152     A regular expression can extend over several lines of input; the newlines are
153 nigel 23 included in it. See the testinput files for many examples.
154 nigel 3
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:
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)
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()
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.
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.
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.
187     $ pcretest
188     Testing Perl-Compatible Regular Expressions
189     PCRE version 0.90 08-Sep-1997
191 nigel 23 re> /^abc(\d+)/
192     data> abc123
193     0: abc123
194     1: 123
195     data> xyz
196 nigel 3 No match
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.
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.
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.
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.
213     If the option -s is given to pcretest, it outputs the size of each compiled
214     pattern after it has been compiled.
216 nigel 23 If the -t option is given, each compile, study, and match is run 10000 times
217 nigel 3 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 nigel 23 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 nigel 3
225     The perltest program
226     --------------------
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 nigel 23 input patterns can be followed only by Perl's lower case options. The contents
231     of testinput and testinput3 meet this condition.
232 nigel 3
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.
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 nigel 23 test some features of PCRE. It also contains malformed regular expressions, in
243     order to check that PCRE diagnoses them correctly.
244 nigel 3
245     Philip Hazel <ph10@cam.ac.uk>
246 nigel 23 September 1998

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