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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 nigel 25 * *
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 nigel 23 *******************************************************************************
21 nigel 3 The distribution should contain the following files:
23     ChangeLog log of changes to the code
24     Makefile for building PCRE
25     README this file
26 nigel 23 RunTest a shell script for running tests
27 nigel 3 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 nigel 25 deftables.c auxiliary program for building chartables.c
31     maketables.c )
32 nigel 3 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 nigel 23 testinput test data, compatible with Perl 5.004 and 5.005
43 nigel 3 testinput2 test data for error messages and non-Perl things
44 nigel 23 testinput3 test data, compatible with Perl 5.005
45 nigel 25 testinput4 test data for locale-specific tests
46 nigel 3 testoutput test results corresponding to testinput
47     testoutput2 test results corresponding to testinput2
48 nigel 25 testoutput3 test results corresponding to testinput3
49     testoutput4 test results corresponding to testinput4
50 nigel 3
51 nigel 23 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 nigel 3
56 nigel 23 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 nigel 3
61 nigel 23 To run pcretest on just one of the test files, give its number as an argument
62     to RunTest, for example:
63 nigel 3
64 nigel 23 RunTest 3
65 nigel 3
66 nigel 23 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 nigel 3
72 nigel 23 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 nigel 7
75 nigel 25 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
83     ** Failed to set locale "fr"
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.
88 nigel 3 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).
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).
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 nigel 23 uses the POSIX API, it will have to be renamed or pointed at by a link.
105 nigel 3
107     Character tables
108     ----------------
110 nigel 25 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 nigel 3
117 nigel 25 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 nigel 3
126 nigel 25 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.
131     The final 256-byte table has bits indicating various character types, as
132 nigel 3 follows:
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
141     You should not alter the set of characters that contain the 128 bit, as that
142     will cause PCRE to malfunction.
145     The pcretest program
146     --------------------
148     This program is intended for testing PCRE, but it can also be used for
149     experimenting with regular expressions.
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.
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
162     /(a|bc)x+yz/
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.
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.
171 nigel 25 The /L option must be followed directly by the name of a locale, for example,
173     /pattern/Lfr
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.
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.
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.
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.
193 nigel 3 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.
199     A regular expression can extend over several lines of input; the newlines are
200 nigel 23 included in it. See the testinput files for many examples.
201 nigel 3
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:
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)
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()
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.
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.
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.
234     $ pcretest
235     Testing Perl-Compatible Regular Expressions
236     PCRE version 0.90 08-Sep-1997
238 nigel 23 re> /^abc(\d+)/
239     data> abc123
240     0: abc123
241     1: 123
242     data> xyz
243 nigel 3 No match
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.
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.
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.
256 nigel 25 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 nigel 3
260     If the option -s is given to pcretest, it outputs the size of each compiled
261     pattern after it has been compiled.
263 nigel 23 If the -t option is given, each compile, study, and match is run 10000 times
264 nigel 3 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 nigel 23 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 nigel 3
272     The perltest program
273     --------------------
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 nigel 23 input patterns can be followed only by Perl's lower case options. The contents
278     of testinput and testinput3 meet this condition.
279 nigel 3
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.
287 nigel 25 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 nigel 3
293     Philip Hazel <ph10@cam.ac.uk>
294 nigel 25 October 1998

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