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1 PCRETEST(1) PCRETEST(1)
2
3
4 NAME
5 pcretest - a program for testing Perl-compatible regular expressions.
6
7
8 SYNOPSIS
9
10 pcretest [-C] [-d] [-dfa] [-i] [-m] [-o osize] [-p] [-t] [source]
11 [destination]
12
13 pcretest was written as a test program for the PCRE regular expression
14 library itself, but it can also be used for experimenting with regular
15 expressions. This document describes the features of the test program;
16 for details of the regular expressions themselves, see the pcrepattern
17 documentation. For details of the PCRE library function calls and their
18 options, see the pcreapi documentation.
19
20
21 OPTIONS
22
23 -C Output the version number of the PCRE library, and all avail-
24 able information about the optional features that are
25 included, and then exit.
26
27 -d Behave as if each regex has the /D (debug) modifier; the
28 internal form is output after compilation.
29
30 -dfa Behave as if each data line contains the \D escape sequence;
31 this causes the alternative matching function,
32 pcre_dfa_exec(), to be used instead of the standard
33 pcre_exec() function (more detail is given below).
34
35 -i Behave as if each regex has the /I modifier; information
36 about the compiled pattern is given after compilation.
37
38 -m Output the size of each compiled pattern after it has been
39 compiled. This is equivalent to adding /M to each regular
40 expression. For compatibility with earlier versions of
41 pcretest, -s is a synonym for -m.
42
43 -o osize Set the number of elements in the output vector that is used
44 when calling pcre_exec() to be osize. The default value is
45 45, which is enough for 14 capturing subexpressions. The vec-
46 tor size can be changed for individual matching calls by
47 including \O in the data line (see below).
48
49 -p Behave as if each regex has the /P modifier; the POSIX wrap-
50 per API is used to call PCRE. None of the other options has
51 any effect when -p is set.
52
53 -t Run each compile, study, and match many times with a timer,
54 and output resulting time per compile or match (in millisec-
55 onds). Do not set -m with -t, because you will then get the
56 size output a zillion times, and the timing will be dis-
57 torted.
58
59
60 DESCRIPTION
61
62 If pcretest is given two filename arguments, it reads from the first
63 and writes to the second. If it is given only one filename argument, it
64 reads from that file and writes to stdout. Otherwise, it reads from
65 stdin and writes to stdout, and prompts for each line of input, using
66 "re>" to prompt for regular expressions, and "data>" to prompt for data
67 lines.
68
69 The program handles any number of sets of input on a single input file.
70 Each set starts with a regular expression, and continues with any num-
71 ber of data lines to be matched against the pattern.
72
73 Each data line is matched separately and independently. If you want to
74 do multiple-line matches, you have to use the \n escape sequence in a
75 single line of input to encode the newline characters. The maximum
76 length of data line is 30,000 characters.
77
78 An empty line signals the end of the data lines, at which point a new
79 regular expression is read. The regular expressions are given enclosed
80 in any non-alphanumeric delimiters other than backslash, for example
81
82 /(a|bc)x+yz/
83
84 White space before the initial delimiter is ignored. A regular expres-
85 sion may be continued over several input lines, in which case the new-
86 line characters are included within it. It is possible to include the
87 delimiter within the pattern by escaping it, for example
88
89 /abc\/def/
90
91 If you do so, the escape and the delimiter form part of the pattern,
92 but since delimiters are always non-alphanumeric, this does not affect
93 its interpretation. If the terminating delimiter is immediately fol-
94 lowed by a backslash, for example,
95
96 /abc/\
97
98 then a backslash is added to the end of the pattern. This is done to
99 provide a way of testing the error condition that arises if a pattern
100 finishes with a backslash, because
101
102 /abc\/
103
104 is interpreted as the first line of a pattern that starts with "abc/",
105 causing pcretest to read the next line as a continuation of the regular
106 expression.
107
108
109 PATTERN MODIFIERS
110
111 A pattern may be followed by any number of modifiers, which are mostly
112 single characters. Following Perl usage, these are referred to below
113 as, for example, "the /i modifier", even though the delimiter of the
114 pattern need not always be a slash, and no slash is used when writing
115 modifiers. Whitespace may appear between the final pattern delimiter
116 and the first modifier, and between the modifiers themselves.
117
118 The /i, /m, /s, and /x modifiers set the PCRE_CASELESS, PCRE_MULTILINE,
119 PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when pcre_com-
120 pile() is called. These four modifier letters have the same effect as
121 they do in Perl. For example:
122
123 /caseless/i
124
125 The following table shows additional modifiers for setting PCRE options
126 that do not correspond to anything in Perl:
127
128 /A PCRE_ANCHORED
129 /C PCRE_AUTO_CALLOUT
130 /E PCRE_DOLLAR_ENDONLY
131 /f PCRE_FIRSTLINE
132 /N PCRE_NO_AUTO_CAPTURE
133 /U PCRE_UNGREEDY
134 /X PCRE_EXTRA
135
136 Searching for all possible matches within each subject string can be
137 requested by the /g or /G modifier. After finding a match, PCRE is
138 called again to search the remainder of the subject string. The differ-
139 ence between /g and /G is that the former uses the startoffset argument
140 to pcre_exec() to start searching at a new point within the entire
141 string (which is in effect what Perl does), whereas the latter passes
142 over a shortened substring. This makes a difference to the matching
143 process if the pattern begins with a lookbehind assertion (including \b
144 or \B).
145
146 If any call to pcre_exec() in a /g or /G sequence matches an empty
147 string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
148 flags set in order to search for another, non-empty, match at the same
149 point. If this second match fails, the start offset is advanced by
150 one, and the normal match is retried. This imitates the way Perl han-
151 dles such cases when using the /g modifier or the split() function.
152
153 There are yet more modifiers for controlling the way pcretest operates.
154
155 The /+ modifier requests that as well as outputting the substring that
156 matched the entire pattern, pcretest should in addition output the
157 remainder of the subject string. This is useful for tests where the
158 subject contains multiple copies of the same substring.
159
160 The /L modifier must be followed directly by the name of a locale, for
161 example,
162
163 /pattern/Lfr_FR
164
165 For this reason, it must be the last modifier. The given locale is set,
166 pcre_maketables() is called to build a set of character tables for the
167 locale, and this is then passed to pcre_compile() when compiling the
168 regular expression. Without an /L modifier, NULL is passed as the
169 tables pointer; that is, /L applies only to the expression on which it
170 appears.
171
172 The /I modifier requests that pcretest output information about the
173 compiled pattern (whether it is anchored, has a fixed first character,
174 and so on). It does this by calling pcre_fullinfo() after compiling a
175 pattern. If the pattern is studied, the results of that are also out-
176 put.
177
178 The /D modifier is a PCRE debugging feature, which also assumes /I. It
179 causes the internal form of compiled regular expressions to be output
180 after compilation. If the pattern was studied, the information returned
181 is also output.
182
183 The /F modifier causes pcretest to flip the byte order of the fields in
184 the compiled pattern that contain 2-byte and 4-byte numbers. This
185 facility is for testing the feature in PCRE that allows it to execute
186 patterns that were compiled on a host with a different endianness. This
187 feature is not available when the POSIX interface to PCRE is being
188 used, that is, when the /P pattern modifier is specified. See also the
189 section about saving and reloading compiled patterns below.
190
191 The /S modifier causes pcre_study() to be called after the expression
192 has been compiled, and the results used when the expression is matched.
193
194 The /M modifier causes the size of memory block used to hold the com-
195 piled pattern to be output.
196
197 The /P modifier causes pcretest to call PCRE via the POSIX wrapper API
198 rather than its native API. When this is done, all other modifiers
199 except /i, /m, and /+ are ignored. REG_ICASE is set if /i is present,
200 and REG_NEWLINE is set if /m is present. The wrapper functions force
201 PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set.
202
203 The /8 modifier causes pcretest to call PCRE with the PCRE_UTF8 option
204 set. This turns on support for UTF-8 character handling in PCRE, pro-
205 vided that it was compiled with this support enabled. This modifier
206 also causes any non-printing characters in output strings to be printed
207 using the \x{hh...} notation if they are valid UTF-8 sequences.
208
209 If the /? modifier is used with /8, it causes pcretest to call
210 pcre_compile() with the PCRE_NO_UTF8_CHECK option, to suppress the
211 checking of the string for UTF-8 validity.
212
213
214 DATA LINES
215
216 Before each data line is passed to pcre_exec(), leading and trailing
217 whitespace is removed, and it is then scanned for \ escapes. Some of
218 these are pretty esoteric features, intended for checking out some of
219 the more complicated features of PCRE. If you are just testing "ordi-
220 nary" regular expressions, you probably don't need any of these. The
221 following escapes are recognized:
222
223 \a alarm (= BEL)
224 \b backspace
225 \e escape
226 \f formfeed
227 \n newline
228 \r carriage return
229 \t tab
230 \v vertical tab
231 \nnn octal character (up to 3 octal digits)
232 \xhh hexadecimal character (up to 2 hex digits)
233 \x{hh...} hexadecimal character, any number of digits
234 in UTF-8 mode
235 \A pass the PCRE_ANCHORED option to pcre_exec()
236 \B pass the PCRE_NOTBOL option to pcre_exec()
237 \Cdd call pcre_copy_substring() for substring dd
238 after a successful match (number less than 32)
239 \Cname call pcre_copy_named_substring() for substring
240 "name" after a successful match (name termin-
241 ated by next non alphanumeric character)
242 \C+ show the current captured substrings at callout
243 time
244 \C- do not supply a callout function
245 \C!n return 1 instead of 0 when callout number n is
246 reached
247 \C!n!m return 1 instead of 0 when callout number n is
248 reached for the nth time
249 \C*n pass the number n (may be negative) as callout
250 data; this is used as the callout return value
251 \D use the pcre_dfa_exec() match function
252 \F only shortest match for pcre_dfa_exec()
253 \Gdd call pcre_get_substring() for substring dd
254 after a successful match (number less than 32)
255 \Gname call pcre_get_named_substring() for substring
256 "name" after a successful match (name termin-
257 ated by next non-alphanumeric character)
258 \L call pcre_get_substringlist() after a
259 successful match
260 \M discover the minimum MATCH_LIMIT setting
261 \N pass the PCRE_NOTEMPTY option to pcre_exec()
262 \Odd set the size of the output vector passed to
263 pcre_exec() to dd (any number of digits)
264 \P pass the PCRE_PARTIAL option to pcre_exec()
265 or pcre_dfa_exec()
266 \R pass the PCRE_DFA_RESTART option to pcre_dfa_exec()
267 \S output details of memory get/free calls during matching
268 \Z pass the PCRE_NOTEOL option to pcre_exec()
269 \? pass the PCRE_NO_UTF8_CHECK option to
270 pcre_exec()
271 \>dd start the match at offset dd (any number of digits);
272 this sets the startoffset argument for pcre_exec()
273
274 A backslash followed by anything else just escapes the anything else.
275 If the very last character is a backslash, it is ignored. This gives a
276 way of passing an empty line as data, since a real empty line termi-
277 nates the data input.
278
279 If \M is present, pcretest calls pcre_exec() several times, with dif-
280 ferent values in the match_limit field of the pcre_extra data struc-
281 ture, until it finds the minimum number that is needed for pcre_exec()
282 to complete. This number is a measure of the amount of recursion and
283 backtracking that takes place, and checking it out can be instructive.
284 For most simple matches, the number is quite small, but for patterns
285 with very large numbers of matching possibilities, it can become large
286 very quickly with increasing length of subject string.
287
288 When \O is used, the value specified may be higher or lower than the
289 size set by the -O command line option (or defaulted to 45); \O applies
290 only to the call of pcre_exec() for the line in which it appears.
291
292 If the /P modifier was present on the pattern, causing the POSIX wrap-
293 per API to be used, only \B and \Z have any effect, causing REG_NOTBOL
294 and REG_NOTEOL to be passed to regexec() respectively.
295
296 The use of \x{hh...} to represent UTF-8 characters is not dependent on
297 the use of the /8 modifier on the pattern. It is recognized always.
298 There may be any number of hexadecimal digits inside the braces. The
299 result is from one to six bytes, encoded according to the UTF-8 rules.
300
301
302 THE ALTERNATIVE MATCHING FUNCTION
303
304 By default, pcretest uses the standard PCRE matching function,
305 pcre_exec() to match each data line. From release 6.0, PCRE supports an
306 alternative matching function, pcre_dfa_test(), which operates in a
307 different way, and has some restrictions. The differences between the
308 two functions are described in the pcrematching documentation.
309
310 If a data line contains the \D escape sequence, or if the command line
311 contains the -dfa option, the alternative matching function is called.
312 This function finds all possible matches at a given point. If, however,
313 the \F escape sequence is present in the data line, it stops after the
314 first match is found. This is always the shortest possible match.
315
316
317 DEFAULT OUTPUT FROM PCRETEST
318
319 This section describes the output when the normal matching function,
320 pcre_exec(), is being used.
321
322 When a match succeeds, pcretest outputs the list of captured substrings
323 that pcre_exec() returns, starting with number 0 for the string that
324 matched the whole pattern. Otherwise, it outputs "No match" or "Partial
325 match" when pcre_exec() returns PCRE_ERROR_NOMATCH or PCRE_ERROR_PAR-
326 TIAL, respectively, and otherwise the PCRE negative error number. Here
327 is an example of an interactive pcretest run.
328
329 $ pcretest
330 PCRE version 5.00 07-Sep-2004
331
332 re> /^abc(\d+)/
333 data> abc123
334 0: abc123
335 1: 123
336 data> xyz
337 No match
338
339 If the strings contain any non-printing characters, they are output as
340 \0x escapes, or as \x{...} escapes if the /8 modifier was present on
341 the pattern. If the pattern has the /+ modifier, the output for sub-
342 string 0 is followed by the the rest of the subject string, identified
343 by "0+" like this:
344
345 re> /cat/+
346 data> cataract
347 0: cat
348 0+ aract
349
350 If the pattern has the /g or /G modifier, the results of successive
351 matching attempts are output in sequence, like this:
352
353 re> /\Bi(\w\w)/g
354 data> Mississippi
355 0: iss
356 1: ss
357 0: iss
358 1: ss
359 0: ipp
360 1: pp
361
362 "No match" is output only if the first match attempt fails.
363
364 If any of the sequences \C, \G, or \L are present in a data line that
365 is successfully matched, the substrings extracted by the convenience
366 functions are output with C, G, or L after the string number instead of
367 a colon. This is in addition to the normal full list. The string length
368 (that is, the return from the extraction function) is given in paren-
369 theses after each string for \C and \G.
370
371 Note that while patterns can be continued over several lines (a plain
372 ">" prompt is used for continuations), data lines may not. However new-
373 lines can be included in data by means of the \n escape.
374
375
376 OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION
377
378 When the alternative matching function, pcre_dfa_exec(), is used (by
379 means of the \D escape sequence or the -dfa command line option), the
380 output consists of a list of all the matches that start at the first
381 point in the subject where there is at least one match. For example:
382
383 re> /(tang|tangerine|tan)/
384 data> yellow tangerine\D
385 0: tangerine
386 1: tang
387 2: tan
388
389 (Using the normal matching function on this data finds only "tang".)
390 The longest matching string is always given first (and numbered zero).
391
392 If /gP is present on the pattern, the search for further matches
393 resumes at the end of the longest match. For example:
394
395 re> /(tang|tangerine|tan)/g
396 data> yellow tangerine and tangy sultana\D
397 0: tangerine
398 1: tang
399 2: tan
400 0: tang
401 1: tan
402 0: tan
403
404 Since the matching function does not support substring capture, the
405 escape sequences that are concerned with captured substrings are not
406 relevant.
407
408
409 RESTARTING AFTER A PARTIAL MATCH
410
411 When the alternative matching function has given the PCRE_ERROR_PARTIAL
412 return, indicating that the subject partially matched the pattern, you
413 can restart the match with additional subject data by means of the \R
414 escape sequence. For example:
415
416 re> /^?(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)$/
417 data> 23ja\P\D
418 Partial match: 23ja
419 data> n05\R\D
420 0: n05
421
422 For further information about partial matching, see the pcrepartial
423 documentation.
424
425
426 CALLOUTS
427
428 If the pattern contains any callout requests, pcretest's callout func-
429 tion is called during matching. This works with both matching func-
430 tions. By default, the called function displays the callout number, the
431 start and current positions in the text at the callout time, and the
432 next pattern item to be tested. For example, the output
433
434 --->pqrabcdef
435 0 ^ ^ \d
436
437 indicates that callout number 0 occurred for a match attempt starting
438 at the fourth character of the subject string, when the pointer was at
439 the seventh character of the data, and when the next pattern item was
440 \d. Just one circumflex is output if the start and current positions
441 are the same.
442
443 Callouts numbered 255 are assumed to be automatic callouts, inserted as
444 a result of the /C pattern modifier. In this case, instead of showing
445 the callout number, the offset in the pattern, preceded by a plus, is
446 output. For example:
447
448 re> /\d?[A-E]\*/C
449 data> E*
450 --->E*
451 +0 ^ \d?
452 +3 ^ [A-E]
453 +8 ^^ \*
454 +10 ^ ^
455 0: E*
456
457 The callout function in pcretest returns zero (carry on matching) by
458 default, but you can use a \C item in a data line (as described above)
459 to change this.
460
461 Inserting callouts can be helpful when using pcretest to check compli-
462 cated regular expressions. For further information about callouts, see
463 the pcrecallout documentation.
464
465
466 SAVING AND RELOADING COMPILED PATTERNS
467
468 The facilities described in this section are not available when the
469 POSIX inteface to PCRE is being used, that is, when the /P pattern mod-
470 ifier is specified.
471
472 When the POSIX interface is not in use, you can cause pcretest to write
473 a compiled pattern to a file, by following the modifiers with > and a
474 file name. For example:
475
476 /pattern/im >/some/file
477
478 See the pcreprecompile documentation for a discussion about saving and
479 re-using compiled patterns.
480
481 The data that is written is binary. The first eight bytes are the
482 length of the compiled pattern data followed by the length of the
483 optional study data, each written as four bytes in big-endian order
484 (most significant byte first). If there is no study data (either the
485 pattern was not studied, or studying did not return any data), the sec-
486 ond length is zero. The lengths are followed by an exact copy of the
487 compiled pattern. If there is additional study data, this follows imme-
488 diately after the compiled pattern. After writing the file, pcretest
489 expects to read a new pattern.
490
491 A saved pattern can be reloaded into pcretest by specifing < and a file
492 name instead of a pattern. The name of the file must not contain a <
493 character, as otherwise pcretest will interpret the line as a pattern
494 delimited by < characters. For example:
495
496 re> </some/file
497 Compiled regex loaded from /some/file
498 No study data
499
500 When the pattern has been loaded, pcretest proceeds to read data lines
501 in the usual way.
502
503 You can copy a file written by pcretest to a different host and reload
504 it there, even if the new host has opposite endianness to the one on
505 which the pattern was compiled. For example, you can compile on an i86
506 machine and run on a SPARC machine.
507
508 File names for saving and reloading can be absolute or relative, but
509 note that the shell facility of expanding a file name that starts with
510 a tilde (~) is not available.
511
512 The ability to save and reload files in pcretest is intended for test-
513 ing and experimentation. It is not intended for production use because
514 only a single pattern can be written to a file. Furthermore, there is
515 no facility for supplying custom character tables for use with a
516 reloaded pattern. If the original pattern was compiled with custom
517 tables, an attempt to match a subject string using a reloaded pattern
518 is likely to cause pcretest to crash. Finally, if you attempt to load
519 a file that is not in the correct format, the result is undefined.
520
521
522 AUTHOR
523
524 Philip Hazel
525 University Computing Service,
526 Cambridge CB2 3QG, England.
527
528 Last updated: 28 February 2005
529 Copyright (c) 1997-2005 University of Cambridge.

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