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1 NAME
2 pcretest - a program for testing Perl-compatible regular
3 expressions.
4
5
6 SYNOPSIS
7 pcretest [-d] [-i] [-m] [-o osize] [-p] [-t] [source] [des-
8 tination]
9
10 pcretest was written as a test program for the PCRE regular
11 expression library itself, but it can also be used for
12 experimenting with regular expressions. This document
13 describes the features of the test program; for details of
14 the regular expressions themselves, see the pcrepattern
15 documentation. For details of PCRE and its options, see the
16 pcreapi documentation.
17
18
19 OPTIONS
20
21
22 -C Output the version number of the PCRE library, and
23 all available information about the optional
24 features that are included, and then exit.
25
26 -d Behave as if each regex had the /D modifier (see
27 below); the internal form is output after compila-
28 tion.
29
30 -i Behave as if each regex had the /I modifier;
31 information about the compiled pattern is given
32 after compilation.
33
34 -m Output the size of each compiled pattern after it
35 has been compiled. This is equivalent to adding /M
36 to each regular expression. For compatibility with
37 earlier versions of pcretest, -s is a synonym for
38 -m.
39
40 -o osize Set the number of elements in the output vector
41 that is used when calling PCRE to be osize. The
42 default value is 45, which is enough for 14 cap-
43 turing subexpressions. The vector size can be
44 changed for individual matching calls by including
45 \O in the data line (see below).
46
47 -p Behave as if each regex has /P modifier; the POSIX
48 wrapper API is used to call PCRE. None of the
49 other options has any effect when -p is set.
50
51 -t Run each compile, study, and match many times with
52 a timer, and output resulting time per compile or
53 match (in milliseconds). Do not set -t with -m,
54 because you will then get the size output 20000
55 times and the timing will be distorted.
56
57
58 DESCRIPTION
59
60 If pcretest is given two filename arguments, it reads from
61 the first and writes to the second. If it is given only one
62 filename argument, it reads from that file and writes to
63 stdout. Otherwise, it reads from stdin and writes to stdout,
64 and prompts for each line of input, using "re>" to prompt
65 for regular expressions, and "data>" to prompt for data
66 lines.
67
68 The program handles any number of sets of input on a single
69 input file. Each set starts with a regular expression, and
70 continues with any number of data lines to be matched
71 against the pattern.
72
73 Each line is matched separately and independently. If you
74 want to do multiple-line matches, you have to use the \n
75 escape sequence in a single line of input to encode the new-
76 line characters. The maximum length of data line is 30,000
77 characters.
78
79 An empty line signals the end of the data lines, at which
80 point a new regular expression is read. The regular expres-
81 sions are given enclosed in any non-alphameric delimiters
82 other than backslash, for example
83
84 /(a|bc)x+yz/
85
86 White space before the initial delimiter is ignored. A regu-
87 lar expression may be continued over several input lines, in
88 which case the newline characters are included within it. It
89 is possible to include the delimiter within the pattern by
90 escaping it, for example
91
92 /abc\/def/
93
94 If you do so, the escape and the delimiter form part of the
95 pattern, but since delimiters are always non-alphameric,
96 this does not affect its interpretation. If the terminating
97 delimiter is immediately followed by a backslash, for exam-
98 ple,
99
100 /abc/\
101
102 then a backslash is added to the end of the pattern. This is
103 done to provide a way of testing the error condition that
104 arises if a pattern finishes with a backslash, because
105
106 /abc\/
107
108 is interpreted as the first line of a pattern that starts
109 with "abc/", causing pcretest to read the next line as a
110 continuation of the regular expression.
111
112
113 PATTERN MODIFIERS
114
115 The pattern may be followed by i, m, s, or x to set the
116 PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED
117 options, respectively. For example:
118
119 /caseless/i
120
121 These modifier letters have the same effect as they do in
122 Perl. There are others which set PCRE options that do not
123 correspond to anything in Perl: /A, /E, and /X set
124 PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respec-
125 tively.
126
127 Searching for all possible matches within each subject
128 string can be requested by the /g or /G modifier. After
129 finding a match, PCRE is called again to search the
130 remainder of the subject string. The difference between /g
131 and /G is that the former uses the startoffset argument to
132 pcre_exec() to start searching at a new point within the
133 entire string (which is in effect what Perl does), whereas
134 the latter passes over a shortened substring. This makes a
135 difference to the matching process if the pattern begins
136 with a lookbehind assertion (including \b or \B).
137
138 If any call to pcre_exec() in a /g or /G sequence matches an
139 empty string, the next call is done with the PCRE_NOTEMPTY
140 and PCRE_ANCHORED flags set in order to search for another,
141 non-empty, match at the same point. If this second match
142 fails, the start offset is advanced by one, and the normal
143 match is retried. This imitates the way Perl handles such
144 cases when using the /g modifier or the split() function.
145
146 There are a number of other modifiers for controlling the
147 way pcretest operates.
148
149 The /+ modifier requests that as well as outputting the sub-
150 string that matched the entire pattern, pcretest should in
151 addition output the remainder of the subject string. This is
152 useful for tests where the subject contains multiple copies
153 of the same substring.
154
155 The /L modifier must be followed directly by the name of a
156 locale, for example,
157
158 /pattern/Lfr
159
160 For this reason, it must be the last modifier letter. The
161 given locale is set, pcre_maketables() is called to build a
162 set of character tables for the locale, and this is then
163 passed to pcre_compile() when compiling the regular expres-
164 sion. Without an /L modifier, NULL is passed as the tables
165 pointer; that is, /L applies only to the expression on which
166 it appears.
167
168 The /I modifier requests that pcretest output information
169 about the compiled expression (whether it is anchored, has a
170 fixed first character, and so on). It does this by calling
171 pcre_fullinfo() after compiling an expression, and output-
172 ting the information it gets back. If the pattern is stu-
173 died, the results of that are also output.
174
175 The /D modifier is a PCRE debugging feature, which also
176 assumes /I. It causes the internal form of compiled regular
177 expressions to be output after compilation. If the pattern
178 was studied, the information returned is also output.
179
180 The /S modifier causes pcre_study() to be called after the
181 expression has been compiled, and the results used when the
182 expression is matched.
183
184 The /M modifier causes the size of memory block used to hold
185 the compiled pattern to be output.
186
187 The /P modifier causes pcretest to call PCRE via the POSIX
188 wrapper API rather than its native API. When this is done,
189 all other modifiers except /i, /m, and /+ are ignored.
190 REG_ICASE is set if /i is present, and REG_NEWLINE is set if
191 /m is present. The wrapper functions force
192 PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless
193 REG_NEWLINE is set.
194
195 The /8 modifier causes pcretest to call PCRE with the
196 PCRE_UTF8 option set. This turns on support for UTF-8 char-
197 acter handling in PCRE, provided that it was compiled with
198 this support enabled. This modifier also causes any non-
199 printing characters in output strings to be printed using
200 the \x{hh...} notation if they are valid UTF-8 sequences.
201
202
203 CALLOUTS
204
205 If the pattern contains any callout requests, pcretest's
206 callout function will be called. By default, it displays the
207 callout number, and the start and current positions in the
208 text at the callout time. For example, the output
209
210 --->pqrabcdef
211 0 ^ ^
212
213 indicates that callout number 0 occurred for a match attempt
214 starting at the fourth character of the subject string, when
215 the pointer was at the seventh character. The callout func-
216 tion returns zero (carry on matching) by default.
217
218 Inserting callouts may be helpful when using pcretest to
219 check complicated regular expressions. For further informa-
220 tion about callouts, see the pcrecallout documentation.
221
222 For testing the PCRE library, additional control of callout
223 behaviour is available via escape sequences in the data, as
224 described in the following section. In particular, it is
225 possible to pass in a number as callout data (the default is
226 zero). If the callout function receives a non-zero number,
227 it returns that value instead of zero.
228
229
230 DATA LINES
231
232 Before each data line is passed to pcre_exec(), leading and
233 trailing whitespace is removed, and it is then scanned for \
234 escapes. Some of these are pretty esoteric features,
235 intended for checking out some of the more complicated
236 features of PCRE. If you are just testing "ordinary" regular
237 expressions, you probably don't need any of these. The fol-
238 lowing escapes are recognized:
239
240 \a alarm (= BEL)
241 \b backspace
242 \e escape
243 \f formfeed
244 \n newline
245 \r carriage return
246 \t tab
247 \v vertical tab
248 \nnn octal character (up to 3 octal digits)
249 \xhh hexadecimal character (up to 2 hex digits)
250 \x{hh...} hexadecimal character, any number of digits
251 in UTF-8 mode
252 \A pass the PCRE_ANCHORED option to pcre_exec()
253 \B pass the PCRE_NOTBOL option to pcre_exec()
254 \Cdd call pcre_copy_substring() for substring dd
255 after a successful match (any decimal number
256 less than 32)
257 \Cname call pcre_copy_named_substring() for substring
258 "name" after a successful match (name termin-
259 ated by next non alphanumeric character)
260 \C+ show the current captured substrings at callout
261 time
262
263 C- do not supply a callout function
264 \C!n return 1 instead of 0 when callout number n is
265 reached
266 \C!n!m return 1 instead of 0 when callout number n is
267 reached for the nth time
268 \C*n pass the number n (may be negative) as callout
269 data
270 \Gdd call pcre_get_substring() for substring dd
271 after a successful match (any decimal number
272 less than 32)
273 \Gname call pcre_get_named_substring() for substring
274 "name" after a successful match (name termin-
275 ated by next non-alphanumeric character)
276 \L call pcre_get_substringlist() after a
277 successful match
278 \M discover the minimum MATCH_LIMIT setting
279 \N pass the PCRE_NOTEMPTY option to pcre_exec()
280 \Odd set the size of the output vector passed to
281 pcre_exec() to dd (any number of decimal
282 digits)
283 \Z pass the PCRE_NOTEOL option to pcre_exec()
284
285 If \M is present, pcretest calls pcre_exec() several times,
286 with different values in the match_limit field of the
287 pcre_extra data structure, until it finds the minimum number
288 that is needed for pcre_exec() to complete. This number is a
289 measure of the amount of recursion and backtracking that
290 takes place, and checking it out can be instructive. For
291 most simple matches, the number is quite small, but for pat-
292 terns with very large numbers of matching possibilities, it
293 can become large very quickly with increasing length of sub-
294 ject string.
295
296 When \O is used, it may be higher or lower than the size set
297 by the -O option (or defaulted to 45); \O applies only to
298 the call of pcre_exec() for the line in which it appears.
299
300 A backslash followed by anything else just escapes the any-
301 thing else. If the very last character is a backslash, it is
302 ignored. This gives a way of passing an empty line as data,
303 since a real empty line terminates the data input.
304
305 If /P was present on the regex, causing the POSIX wrapper
306 API to be used, only B, and Z have any effect, causing
307 REG_NOTBOL and REG_NOTEOL to be passed to regexec() respec-
308 tively.
309
310 The use of \x{hh...} to represent UTF-8 characters is not
311 dependent on the use of the /8 modifier on the pattern. It
312 is recognized always. There may be any number of hexadecimal
313 digits inside the braces. The result is from one to six
314 bytes, encoded according to the UTF-8 rules.
315
316
317 OUTPUT FROM PCRETEST
318
319 When a match succeeds, pcretest outputs the list of captured
320 substrings that pcre_exec() returns, starting with number 0
321 for the string that matched the whole pattern. Here is an
322 example of an interactive pcretest run.
323
324 $ pcretest
325 PCRE version 4.00 08-Jan-2003
326
327 re> /^abc(\d+)/
328 data> abc123
329 0: abc123
330 1: 123
331 data> xyz
332 No match
333
334 If the strings contain any non-printing characters, they are
335 output as \0x escapes, or as \x{...} escapes if the /8
336 modifier was present on the pattern. If the pattern has the
337 /+ modifier, then the output for substring 0 is followed by
338 the the rest of the subject string, identified by "0+" like
339 this:
340
341 re> /cat/+
342 data> cataract
343 0: cat
344 0+ aract
345
346 If the pattern has the /g or /G modifier, the results of
347 successive matching attempts are output in sequence, like
348 this:
349
350 re> /\Bi(\w\w)/g
351 data> Mississippi
352 0: iss
353 1: ss
354 0: iss
355 1: ss
356 0: ipp
357 1: pp
358
359 "No match" is output only if the first match attempt fails.
360
361 If any of the sequences \C, \G, or \L are present in a data
362 line that is successfully matched, the substrings extracted
363 by the convenience functions are output with C, G, or L
364 after the string number instead of a colon. This is in addi-
365 tion to the normal full list. The string length (that is,
366 the return from the extraction function) is given in
367 parentheses after each string for \C and \G.
368
369 Note that while patterns can be continued over several lines
370 (a plain ">" prompt is used for continuations), data lines
371 may not. However newlines can be included in data by means
372 of the \n escape.
373
374
375 AUTHOR
376
377 Philip Hazel <ph10@cam.ac.uk>
378 University Computing Service,
379 Cambridge CB2 3QG, England.
380
381 Last updated: 03 February 2003
382 Copyright (c) 1997-2003 University of Cambridge.

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