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1 .TH PCRETEST 1
2 .SH NAME
3 pcretest - a program for testing Perl-compatible regular expressions.
4 .SH SYNOPSIS
5 .B pcretest "[-d] [-i] [-m] [-o osize] [-p] [-t] [source] [destination]"
6
7 \fBpcretest\fR was written as a test program for the PCRE regular expression
8 library itself, but it can also be used for experimenting with regular
9 expressions. This document describes the features of the test program; for
10 details of the regular expressions themselves, see the
11 .\" HREF
12 \fBpcrepattern\fR
13 .\"
14 documentation. For details of PCRE and its options, see the
15 .\" HREF
16 \fBpcreapi\fR
17 .\"
18 documentation.
19
20 .SH OPTIONS
21 .rs
22 .sp
23 .TP 10
24 \fB-C\fR
25 Output the version number of the PCRE library, and all available information
26 about the optional features that are included, and then exit.
27 .TP 10
28 \fB-d\fR
29 Behave as if each regex had the \fB/D\fR modifier (see below); the internal
30 form is output after compilation.
31 .TP 10
32 \fB-i\fR
33 Behave as if each regex had the \fB/I\fR modifier; information about the
34 compiled pattern is given after compilation.
35 .TP 10
36 \fB-m\fR
37 Output the size of each compiled pattern after it has been compiled. This is
38 equivalent to adding /M to each regular expression. For compatibility with
39 earlier versions of pcretest, \fB-s\fR is a synonym for \fB-m\fR.
40 .TP 10
41 \fB-o\fR \fIosize\fR
42 Set the number of elements in the output vector that is used when calling PCRE
43 to be \fIosize\fR. The default value is 45, which is enough for 14 capturing
44 subexpressions. The vector size can be changed for individual matching calls by
45 including \\O in the data line (see below).
46 .TP 10
47 \fB-p\fR
48 Behave as if each regex has \fB/P\fR modifier; the POSIX wrapper API is used
49 to call PCRE. None of the other options has any effect when \fB-p\fR is set.
50 .TP 10
51 \fB-t\fR
52 Run each compile, study, and match many times with a timer, and output
53 resulting time per compile or match (in milliseconds). Do not set \fB-t\fR with
54 \fB-m\fR, because you will then get the size output 20000 times and the timing
55 will be distorted.
56
57 .SH DESCRIPTION
58 .rs
59 .sp
60 If \fBpcretest\fR is given two filename arguments, it reads from the first and
61 writes to the second. If it is given only one filename argument, it reads from
62 that file and writes to stdout. Otherwise, it reads from stdin and writes to
63 stdout, and prompts for each line of input, using "re>" to prompt for regular
64 expressions, and "data>" to prompt for data lines.
65
66 The program handles any number of sets of input on a single input file. Each
67 set starts with a regular expression, and continues with any number of data
68 lines to be matched against the pattern.
69
70 Each line is matched separately and independently. If you want to do
71 multiple-line matches, you have to use the \\n escape sequence in a single line
72 of input to encode the newline characters. The maximum length of data line is
73 30,000 characters.
74
75 An empty line signals the end of the data lines, at which point a new regular
76 expression is read. The regular expressions are given enclosed in any
77 non-alphameric delimiters other than backslash, for example
78
79 /(a|bc)x+yz/
80
81 White space before the initial delimiter is ignored. A regular expression may
82 be continued over several input lines, in which case the newline characters are
83 included within it. It is possible to include the delimiter within the pattern
84 by escaping it, for example
85
86 /abc\\/def/
87
88 If you do so, the escape and the delimiter form part of the pattern, but since
89 delimiters are always non-alphameric, this does not affect its interpretation.
90 If the terminating delimiter is immediately followed by a backslash, for
91 example,
92
93 /abc/\\
94
95 then a backslash is added to the end of the pattern. This is done to provide a
96 way of testing the error condition that arises if a pattern finishes with a
97 backslash, because
98
99 /abc\\/
100
101 is interpreted as the first line of a pattern that starts with "abc/", causing
102 pcretest to read the next line as a continuation of the regular expression.
103
104 .SH PATTERN MODIFIERS
105 .rs
106 .sp
107 The pattern may be followed by \fBi\fR, \fBm\fR, \fBs\fR, or \fBx\fR to set the
108 PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options,
109 respectively. For example:
110
111 /caseless/i
112
113 These modifier letters have the same effect as they do in Perl. There are
114 others that set PCRE options that do not correspond to anything in Perl:
115 \fB/A\fR, \fB/E\fR, \fB/N\fR, \fB/U\fR, and \fB/X\fR set PCRE_ANCHORED,
116 PCRE_DOLLAR_ENDONLY, PCRE_NO_AUTO_CAPTURE, PCRE_UNGREEDY, and PCRE_EXTRA
117 respectively.
118
119 Searching for all possible matches within each subject string can be requested
120 by the \fB/g\fR or \fB/G\fR modifier. After finding a match, PCRE is called
121 again to search the remainder of the subject string. The difference between
122 \fB/g\fR and \fB/G\fR is that the former uses the \fIstartoffset\fR argument to
123 \fBpcre_exec()\fR to start searching at a new point within the entire string
124 (which is in effect what Perl does), whereas the latter passes over a shortened
125 substring. This makes a difference to the matching process if the pattern
126 begins with a lookbehind assertion (including \\b or \\B).
127
128 If any call to \fBpcre_exec()\fR in a \fB/g\fR or \fB/G\fR sequence matches an
129 empty string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
130 flags set in order to search for another, non-empty, match at the same point.
131 If this second match fails, the start offset is advanced by one, and the normal
132 match is retried. This imitates the way Perl handles such cases when using the
133 \fB/g\fR modifier or the \fBsplit()\fR function.
134
135 There are a number of other modifiers for controlling the way \fBpcretest\fR
136 operates.
137
138 The \fB/+\fR modifier requests that as well as outputting the substring that
139 matched the entire pattern, pcretest should in addition output the remainder of
140 the subject string. This is useful for tests where the subject contains
141 multiple copies of the same substring.
142
143 The \fB/L\fR modifier must be followed directly by the name of a locale, for
144 example,
145
146 /pattern/Lfr
147
148 For this reason, it must be the last modifier letter. The given locale is set,
149 \fBpcre_maketables()\fR is called to build a set of character tables for the
150 locale, and this is then passed to \fBpcre_compile()\fR when compiling the
151 regular expression. Without an \fB/L\fR modifier, NULL is passed as the tables
152 pointer; that is, \fB/L\fR applies only to the expression on which it appears.
153
154 The \fB/I\fR modifier requests that \fBpcretest\fR output information about the
155 compiled expression (whether it is anchored, has a fixed first character, and
156 so on). It does this by calling \fBpcre_fullinfo()\fR after compiling an
157 expression, and outputting the information it gets back. If the pattern is
158 studied, the results of that are also output.
159
160 The \fB/D\fR modifier is a PCRE debugging feature, which also assumes \fB/I\fR.
161 It causes the internal form of compiled regular expressions to be output after
162 compilation. If the pattern was studied, the information returned is also
163 output.
164
165 The \fB/S\fR modifier causes \fBpcre_study()\fR to be called after the
166 expression has been compiled, and the results used when the expression is
167 matched.
168
169 The \fB/M\fR modifier causes the size of memory block used to hold the compiled
170 pattern to be output.
171
172 The \fB/P\fR modifier causes \fBpcretest\fR to call PCRE via the POSIX wrapper
173 API rather than its native API. When this is done, all other modifiers except
174 \fB/i\fR, \fB/m\fR, and \fB/+\fR are ignored. REG_ICASE is set if \fB/i\fR is
175 present, and REG_NEWLINE is set if \fB/m\fR is present. The wrapper functions
176 force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set.
177
178 The \fB/8\fR modifier causes \fBpcretest\fR to call PCRE with the PCRE_UTF8
179 option set. This turns on support for UTF-8 character handling in PCRE,
180 provided that it was compiled with this support enabled. This modifier also
181 causes any non-printing characters in output strings to be printed using the
182 \\x{hh...} notation if they are valid UTF-8 sequences.
183
184 If the \fB/?\fR modifier is used with \fB/8\fR, it causes \fBpcretest\fR to
185 call \fBpcre_compile()\fR with the PCRE_NO_UTF8_CHECK option, to suppress the
186 checking of the string for UTF-8 validity.
187
188 .SH CALLOUTS
189 .rs
190 .sp
191 If the pattern contains any callout requests, \fBpcretest\fR's callout function
192 will be called. By default, it displays the callout number, and the start and
193 current positions in the text at the callout time. For example, the output
194
195 --->pqrabcdef
196 0 ^ ^
197
198 indicates that callout number 0 occurred for a match attempt starting at the
199 fourth character of the subject string, when the pointer was at the seventh
200 character. The callout function returns zero (carry on matching) by default.
201
202 Inserting callouts may be helpful when using \fBpcretest\fR to check
203 complicated regular expressions. For further information about callouts, see
204 the
205 .\" HREF
206 \fBpcrecallout\fR
207 .\"
208 documentation.
209
210 For testing the PCRE library, additional control of callout behaviour is
211 available via escape sequences in the data, as described in the following
212 section. In particular, it is possible to pass in a number as callout data (the
213 default is zero). If the callout function receives a non-zero number, it
214 returns that value instead of zero.
215
216 .SH DATA LINES
217 .rs
218 .sp
219 Before each data line is passed to \fBpcre_exec()\fR, leading and trailing
220 whitespace is removed, and it is then scanned for \\ escapes. Some of these are
221 pretty esoteric features, intended for checking out some of the more
222 complicated features of PCRE. If you are just testing "ordinary" regular
223 expressions, you probably don't need any of these. The following escapes are
224 recognized:
225
226 \\a alarm (= BEL)
227 \\b backspace
228 \\e escape
229 \\f formfeed
230 \\n newline
231 \\r carriage return
232 \\t tab
233 \\v vertical tab
234 \\nnn octal character (up to 3 octal digits)
235 \\xhh hexadecimal character (up to 2 hex digits)
236 \\x{hh...} hexadecimal character, any number of digits
237 in UTF-8 mode
238 \\A pass the PCRE_ANCHORED option to \fBpcre_exec()\fR
239 \\B pass the PCRE_NOTBOL option to \fBpcre_exec()\fR
240 \\Cdd call pcre_copy_substring() for substring dd
241 after a successful match (any decimal number
242 less than 32)
243 \\Cname call pcre_copy_named_substring() for substring
244 "name" after a successful match (name termin-
245 ated by next non alphanumeric character)
246 \\C+ show the current captured substrings at callout
247 time
248 \\C- do not supply a callout function
249 \\C!n return 1 instead of 0 when callout number n is
250 reached
251 \\C!n!m return 1 instead of 0 when callout number n is
252 reached for the nth time
253 \\C*n pass the number n (may be negative) as callout
254 data
255 \\Gdd call pcre_get_substring() for substring dd
256 after a successful match (any decimal number
257 less than 32)
258 \\Gname call pcre_get_named_substring() for substring
259 "name" after a successful match (name termin-
260 ated by next non-alphanumeric character)
261 \\L call pcre_get_substringlist() after a
262 successful match
263 \\M discover the minimum MATCH_LIMIT setting
264 \\N pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fR
265 \\Odd set the size of the output vector passed to
266 \fBpcre_exec()\fR to dd (any number of decimal
267 digits)
268 \\Z pass the PCRE_NOTEOL option to \fBpcre_exec()\fR
269 \\? pass the PCRE_NO_UTF8_CHECK option to
270 \fBpcre_exec()\fR
271
272 If \\M is present, \fBpcretest\fR calls \fBpcre_exec()\fR several times, with
273 different values in the \fImatch_limit\fR field of the \fBpcre_extra\fR data
274 structure, until it finds the minimum number that is needed for
275 \fBpcre_exec()\fR to complete. This number is a measure of the amount of
276 recursion and backtracking that takes place, and checking it out can be
277 instructive. For most simple matches, the number is quite small, but for
278 patterns with very large numbers of matching possibilities, it can become large
279 very quickly with increasing length of subject string.
280
281 When \\O is used, it may be higher or lower than the size set by the \fB-O\fR
282 option (or defaulted to 45); \\O applies only to the call of \fBpcre_exec()\fR
283 for the line in which it appears.
284
285 A backslash followed by anything else just escapes the anything else. If the
286 very last character is a backslash, it is ignored. This gives a way of passing
287 an empty line as data, since a real empty line terminates the data input.
288
289 If \fB/P\fR was present on the regex, causing the POSIX wrapper API to be used,
290 only \fB\B\fR, and \fB\Z\fR have any effect, causing REG_NOTBOL and REG_NOTEOL
291 to be passed to \fBregexec()\fR respectively.
292
293 The use of \\x{hh...} to represent UTF-8 characters is not dependent on the use
294 of the \fB/8\fR modifier on the pattern. It is recognized always. There may be
295 any number of hexadecimal digits inside the braces. The result is from one to
296 six bytes, encoded according to the UTF-8 rules.
297
298 .SH OUTPUT FROM PCRETEST
299 .rs
300 .sp
301 When a match succeeds, pcretest outputs the list of captured substrings that
302 \fBpcre_exec()\fR returns, starting with number 0 for the string that matched
303 the whole pattern. Here is an example of an interactive pcretest run.
304
305 $ pcretest
306 PCRE version 4.00 08-Jan-2003
307
308 re> /^abc(\\d+)/
309 data> abc123
310 0: abc123
311 1: 123
312 data> xyz
313 No match
314
315 If the strings contain any non-printing characters, they are output as \\0x
316 escapes, or as \\x{...} escapes if the \fB/8\fR modifier was present on the
317 pattern. If the pattern has the \fB/+\fR modifier, then the output for
318 substring 0 is followed by the the rest of the subject string, identified by
319 "0+" like this:
320
321 re> /cat/+
322 data> cataract
323 0: cat
324 0+ aract
325
326 If the pattern has the \fB/g\fR or \fB/G\fR modifier, the results of successive
327 matching attempts are output in sequence, like this:
328
329 re> /\\Bi(\\w\\w)/g
330 data> Mississippi
331 0: iss
332 1: ss
333 0: iss
334 1: ss
335 0: ipp
336 1: pp
337
338 "No match" is output only if the first match attempt fails.
339
340 If any of the sequences \fB\\C\fR, \fB\\G\fR, or \fB\\L\fR are present in a
341 data line that is successfully matched, the substrings extracted by the
342 convenience functions are output with C, G, or L after the string number
343 instead of a colon. This is in addition to the normal full list. The string
344 length (that is, the return from the extraction function) is given in
345 parentheses after each string for \fB\\C\fR and \fB\\G\fR.
346
347 Note that while patterns can be continued over several lines (a plain ">"
348 prompt is used for continuations), data lines may not. However newlines can be
349 included in data by means of the \\n escape.
350
351 .SH AUTHOR
352 .rs
353 .sp
354 Philip Hazel <ph10@cam.ac.uk>
355 .br
356 University Computing Service,
357 .br
358 Cambridge CB2 3QG, England.
359
360 .in 0
361 Last updated: 20 August 2003
362 .br
363 Copyright (c) 1997-2003 University of Cambridge.

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