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Revision 426 - (show annotations) (download)
Wed Aug 26 15:38:32 2009 UTC (5 years, 1 month ago) by ph10
File size: 28646 byte(s)
Remove restrictions on pcre_exec() partial matching.

1 .TH PCRETEST 1
2 .SH NAME
3 pcretest - a program for testing Perl-compatible regular expressions.
4 .SH SYNOPSIS
5 .rs
6 .sp
7 .B pcretest "[options] [source] [destination]"
8 .sp
9 \fBpcretest\fP was written as a test program for the PCRE regular expression
10 library itself, but it can also be used for experimenting with regular
11 expressions. This document describes the features of the test program; for
12 details of the regular expressions themselves, see the
13 .\" HREF
14 \fBpcrepattern\fP
15 .\"
16 documentation. For details of the PCRE library function calls and their
17 options, see the
18 .\" HREF
19 \fBpcreapi\fP
20 .\"
21 documentation.
22 .
23 .
24 .SH OPTIONS
25 .rs
26 .TP 10
27 \fB-b\fP
28 Behave as if each regex has the \fB/B\fP (show bytecode) modifier; the internal
29 form is output after compilation.
30 .TP 10
31 \fB-C\fP
32 Output the version number of the PCRE library, and all available information
33 about the optional features that are included, and then exit.
34 .TP 10
35 \fB-d\fP
36 Behave as if each regex has the \fB/D\fP (debug) modifier; the internal
37 form and information about the compiled pattern is output after compilation;
38 \fB-d\fP is equivalent to \fB-b -i\fP.
39 .TP 10
40 \fB-dfa\fP
41 Behave as if each data line contains the \eD escape sequence; this causes the
42 alternative matching function, \fBpcre_dfa_exec()\fP, to be used instead of the
43 standard \fBpcre_exec()\fP function (more detail is given below).
44 .TP 10
45 \fB-help\fP
46 Output a brief summary these options and then exit.
47 .TP 10
48 \fB-i\fP
49 Behave as if each regex has the \fB/I\fP modifier; information about the
50 compiled pattern is given after compilation.
51 .TP 10
52 \fB-M\fP
53 Behave as if each data line contains the \eM escape sequence; this causes
54 PCRE to discover the minimum MATCH_LIMIT and MATCH_LIMIT_RECURSION settings by
55 calling \fBpcre_exec()\fP repeatedly with different limits.
56 .TP 10
57 \fB-m\fP
58 Output the size of each compiled pattern after it has been compiled. This is
59 equivalent to adding \fB/M\fP to each regular expression. For compatibility
60 with earlier versions of pcretest, \fB-s\fP is a synonym for \fB-m\fP.
61 .TP 10
62 \fB-o\fP \fIosize\fP
63 Set the number of elements in the output vector that is used when calling
64 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP to be \fIosize\fP. The default value
65 is 45, which is enough for 14 capturing subexpressions for \fBpcre_exec()\fP or
66 22 different matches for \fBpcre_dfa_exec()\fP. The vector size can be
67 changed for individual matching calls by including \eO in the data line (see
68 below).
69 .TP 10
70 \fB-p\fP
71 Behave as if each regex has the \fB/P\fP modifier; the POSIX wrapper API is
72 used to call PCRE. None of the other options has any effect when \fB-p\fP is
73 set.
74 .TP 10
75 \fB-q\fP
76 Do not output the version number of \fBpcretest\fP at the start of execution.
77 .TP 10
78 \fB-S\fP \fIsize\fP
79 On Unix-like systems, set the size of the runtime stack to \fIsize\fP
80 megabytes.
81 .TP 10
82 \fB-t\fP
83 Run each compile, study, and match many times with a timer, and output
84 resulting time per compile or match (in milliseconds). Do not set \fB-m\fP with
85 \fB-t\fP, because you will then get the size output a zillion times, and the
86 timing will be distorted. You can control the number of iterations that are
87 used for timing by following \fB-t\fP with a number (as a separate item on the
88 command line). For example, "-t 1000" would iterate 1000 times. The default is
89 to iterate 500000 times.
90 .TP 10
91 \fB-tm\fP
92 This is like \fB-t\fP except that it times only the matching phase, not the
93 compile or study phases.
94 .
95 .
96 .SH DESCRIPTION
97 .rs
98 .sp
99 If \fBpcretest\fP is given two filename arguments, it reads from the first and
100 writes to the second. If it is given only one filename argument, it reads from
101 that file and writes to stdout. Otherwise, it reads from stdin and writes to
102 stdout, and prompts for each line of input, using "re>" to prompt for regular
103 expressions, and "data>" to prompt for data lines.
104 .P
105 When \fBpcretest\fP is built, a configuration option can specify that it should
106 be linked with the \fBlibreadline\fP library. When this is done, if the input
107 is from a terminal, it is read using the \fBreadline()\fP function. This
108 provides line-editing and history facilities. The output from the \fB-help\fP
109 option states whether or not \fBreadline()\fP will be used.
110 .P
111 The program handles any number of sets of input on a single input file. Each
112 set starts with a regular expression, and continues with any number of data
113 lines to be matched against the pattern.
114 .P
115 Each data line is matched separately and independently. If you want to do
116 multi-line matches, you have to use the \en escape sequence (or \er or \er\en,
117 etc., depending on the newline setting) in a single line of input to encode the
118 newline sequences. There is no limit on the length of data lines; the input
119 buffer is automatically extended if it is too small.
120 .P
121 An empty line signals the end of the data lines, at which point a new regular
122 expression is read. The regular expressions are given enclosed in any
123 non-alphanumeric delimiters other than backslash, for example:
124 .sp
125 /(a|bc)x+yz/
126 .sp
127 White space before the initial delimiter is ignored. A regular expression may
128 be continued over several input lines, in which case the newline characters are
129 included within it. It is possible to include the delimiter within the pattern
130 by escaping it, for example
131 .sp
132 /abc\e/def/
133 .sp
134 If you do so, the escape and the delimiter form part of the pattern, but since
135 delimiters are always non-alphanumeric, this does not affect its interpretation.
136 If the terminating delimiter is immediately followed by a backslash, for
137 example,
138 .sp
139 /abc/\e
140 .sp
141 then a backslash is added to the end of the pattern. This is done to provide a
142 way of testing the error condition that arises if a pattern finishes with a
143 backslash, because
144 .sp
145 /abc\e/
146 .sp
147 is interpreted as the first line of a pattern that starts with "abc/", causing
148 pcretest to read the next line as a continuation of the regular expression.
149 .
150 .
151 .SH "PATTERN MODIFIERS"
152 .rs
153 .sp
154 A pattern may be followed by any number of modifiers, which are mostly single
155 characters. Following Perl usage, these are referred to below as, for example,
156 "the \fB/i\fP modifier", even though the delimiter of the pattern need not
157 always be a slash, and no slash is used when writing modifiers. Whitespace may
158 appear between the final pattern delimiter and the first modifier, and between
159 the modifiers themselves.
160 .P
161 The \fB/i\fP, \fB/m\fP, \fB/s\fP, and \fB/x\fP modifiers set the PCRE_CASELESS,
162 PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when
163 \fBpcre_compile()\fP is called. These four modifier letters have the same
164 effect as they do in Perl. For example:
165 .sp
166 /caseless/i
167 .sp
168 The following table shows additional modifiers for setting PCRE options that do
169 not correspond to anything in Perl:
170 .sp
171 \fB/A\fP PCRE_ANCHORED
172 \fB/C\fP PCRE_AUTO_CALLOUT
173 \fB/E\fP PCRE_DOLLAR_ENDONLY
174 \fB/f\fP PCRE_FIRSTLINE
175 \fB/J\fP PCRE_DUPNAMES
176 \fB/N\fP PCRE_NO_AUTO_CAPTURE
177 \fB/U\fP PCRE_UNGREEDY
178 \fB/X\fP PCRE_EXTRA
179 \fB/<JS>\fP PCRE_JAVASCRIPT_COMPAT
180 \fB/<cr>\fP PCRE_NEWLINE_CR
181 \fB/<lf>\fP PCRE_NEWLINE_LF
182 \fB/<crlf>\fP PCRE_NEWLINE_CRLF
183 \fB/<anycrlf>\fP PCRE_NEWLINE_ANYCRLF
184 \fB/<any>\fP PCRE_NEWLINE_ANY
185 \fB/<bsr_anycrlf>\fP PCRE_BSR_ANYCRLF
186 \fB/<bsr_unicode>\fP PCRE_BSR_UNICODE
187 .sp
188 Those specifying line ending sequences are literal strings as shown, but the
189 letters can be in either case. This example sets multiline matching with CRLF
190 as the line ending sequence:
191 .sp
192 /^abc/m<crlf>
193 .sp
194 Details of the meanings of these PCRE options are given in the
195 .\" HREF
196 \fBpcreapi\fP
197 .\"
198 documentation.
199 .
200 .
201 .SS "Finding all matches in a string"
202 .rs
203 .sp
204 Searching for all possible matches within each subject string can be requested
205 by the \fB/g\fP or \fB/G\fP modifier. After finding a match, PCRE is called
206 again to search the remainder of the subject string. The difference between
207 \fB/g\fP and \fB/G\fP is that the former uses the \fIstartoffset\fP argument to
208 \fBpcre_exec()\fP to start searching at a new point within the entire string
209 (which is in effect what Perl does), whereas the latter passes over a shortened
210 substring. This makes a difference to the matching process if the pattern
211 begins with a lookbehind assertion (including \eb or \eB).
212 .P
213 If any call to \fBpcre_exec()\fP in a \fB/g\fP or \fB/G\fP sequence matches an
214 empty string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
215 flags set in order to search for another, non-empty, match at the same point.
216 If this second match fails, the start offset is advanced by one, and the normal
217 match is retried. This imitates the way Perl handles such cases when using the
218 \fB/g\fP modifier or the \fBsplit()\fP function.
219 .
220 .
221 .SS "Other modifiers"
222 .rs
223 .sp
224 There are yet more modifiers for controlling the way \fBpcretest\fP
225 operates.
226 .P
227 The \fB/+\fP modifier requests that as well as outputting the substring that
228 matched the entire pattern, pcretest should in addition output the remainder of
229 the subject string. This is useful for tests where the subject contains
230 multiple copies of the same substring.
231 .P
232 The \fB/B\fP modifier is a debugging feature. It requests that \fBpcretest\fP
233 output a representation of the compiled byte code after compilation. Normally
234 this information contains length and offset values; however, if \fB/Z\fP is
235 also present, this data is replaced by spaces. This is a special feature for
236 use in the automatic test scripts; it ensures that the same output is generated
237 for different internal link sizes.
238 .P
239 The \fB/L\fP modifier must be followed directly by the name of a locale, for
240 example,
241 .sp
242 /pattern/Lfr_FR
243 .sp
244 For this reason, it must be the last modifier. The given locale is set,
245 \fBpcre_maketables()\fP is called to build a set of character tables for the
246 locale, and this is then passed to \fBpcre_compile()\fP when compiling the
247 regular expression. Without an \fB/L\fP modifier, NULL is passed as the tables
248 pointer; that is, \fB/L\fP applies only to the expression on which it appears.
249 .P
250 The \fB/I\fP modifier requests that \fBpcretest\fP output information about the
251 compiled pattern (whether it is anchored, has a fixed first character, and
252 so on). It does this by calling \fBpcre_fullinfo()\fP after compiling a
253 pattern. If the pattern is studied, the results of that are also output.
254 .P
255 The \fB/D\fP modifier is a PCRE debugging feature, and is equivalent to
256 \fB/BI\fP, that is, both the \fB/B\fP and the \fB/I\fP modifiers.
257 .P
258 The \fB/F\fP modifier causes \fBpcretest\fP to flip the byte order of the
259 fields in the compiled pattern that contain 2-byte and 4-byte numbers. This
260 facility is for testing the feature in PCRE that allows it to execute patterns
261 that were compiled on a host with a different endianness. This feature is not
262 available when the POSIX interface to PCRE is being used, that is, when the
263 \fB/P\fP pattern modifier is specified. See also the section about saving and
264 reloading compiled patterns below.
265 .P
266 The \fB/S\fP modifier causes \fBpcre_study()\fP to be called after the
267 expression has been compiled, and the results used when the expression is
268 matched.
269 .P
270 The \fB/M\fP modifier causes the size of memory block used to hold the compiled
271 pattern to be output.
272 .P
273 The \fB/P\fP modifier causes \fBpcretest\fP to call PCRE via the POSIX wrapper
274 API rather than its native API. When this is done, all other modifiers except
275 \fB/i\fP, \fB/m\fP, and \fB/+\fP are ignored. REG_ICASE is set if \fB/i\fP is
276 present, and REG_NEWLINE is set if \fB/m\fP is present. The wrapper functions
277 force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set.
278 .P
279 The \fB/8\fP modifier causes \fBpcretest\fP to call PCRE with the PCRE_UTF8
280 option set. This turns on support for UTF-8 character handling in PCRE,
281 provided that it was compiled with this support enabled. This modifier also
282 causes any non-printing characters in output strings to be printed using the
283 \ex{hh...} notation if they are valid UTF-8 sequences.
284 .P
285 If the \fB/?\fP modifier is used with \fB/8\fP, it causes \fBpcretest\fP to
286 call \fBpcre_compile()\fP with the PCRE_NO_UTF8_CHECK option, to suppress the
287 checking of the string for UTF-8 validity.
288 .
289 .
290 .SH "DATA LINES"
291 .rs
292 .sp
293 Before each data line is passed to \fBpcre_exec()\fP, leading and trailing
294 whitespace is removed, and it is then scanned for \e escapes. Some of these are
295 pretty esoteric features, intended for checking out some of the more
296 complicated features of PCRE. If you are just testing "ordinary" regular
297 expressions, you probably don't need any of these. The following escapes are
298 recognized:
299 .sp
300 \ea alarm (BEL, \ex07)
301 \eb backspace (\ex08)
302 \ee escape (\ex27)
303 \ef formfeed (\ex0c)
304 \en newline (\ex0a)
305 .\" JOIN
306 \eqdd set the PCRE_MATCH_LIMIT limit to dd
307 (any number of digits)
308 \er carriage return (\ex0d)
309 \et tab (\ex09)
310 \ev vertical tab (\ex0b)
311 \ennn octal character (up to 3 octal digits)
312 \exhh hexadecimal character (up to 2 hex digits)
313 .\" JOIN
314 \ex{hh...} hexadecimal character, any number of digits
315 in UTF-8 mode
316 .\" JOIN
317 \eA pass the PCRE_ANCHORED option to \fBpcre_exec()\fP
318 or \fBpcre_dfa_exec()\fP
319 .\" JOIN
320 \eB pass the PCRE_NOTBOL option to \fBpcre_exec()\fP
321 or \fBpcre_dfa_exec()\fP
322 .\" JOIN
323 \eCdd call pcre_copy_substring() for substring dd
324 after a successful match (number less than 32)
325 .\" JOIN
326 \eCname call pcre_copy_named_substring() for substring
327 "name" after a successful match (name termin-
328 ated by next non alphanumeric character)
329 .\" JOIN
330 \eC+ show the current captured substrings at callout
331 time
332 \eC- do not supply a callout function
333 .\" JOIN
334 \eC!n return 1 instead of 0 when callout number n is
335 reached
336 .\" JOIN
337 \eC!n!m return 1 instead of 0 when callout number n is
338 reached for the nth time
339 .\" JOIN
340 \eC*n pass the number n (may be negative) as callout
341 data; this is used as the callout return value
342 \eD use the \fBpcre_dfa_exec()\fP match function
343 \eF only shortest match for \fBpcre_dfa_exec()\fP
344 .\" JOIN
345 \eGdd call pcre_get_substring() for substring dd
346 after a successful match (number less than 32)
347 .\" JOIN
348 \eGname call pcre_get_named_substring() for substring
349 "name" after a successful match (name termin-
350 ated by next non-alphanumeric character)
351 .\" JOIN
352 \eL call pcre_get_substringlist() after a
353 successful match
354 .\" JOIN
355 \eM discover the minimum MATCH_LIMIT and
356 MATCH_LIMIT_RECURSION settings
357 .\" JOIN
358 \eN pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fP
359 or \fBpcre_dfa_exec()\fP
360 .\" JOIN
361 \eOdd set the size of the output vector passed to
362 \fBpcre_exec()\fP to dd (any number of digits)
363 .\" JOIN
364 \eP pass the PCRE_PARTIAL option to \fBpcre_exec()\fP
365 or \fBpcre_dfa_exec()\fP
366 .\" JOIN
367 \eQdd set the PCRE_MATCH_LIMIT_RECURSION limit to dd
368 (any number of digits)
369 \eR pass the PCRE_DFA_RESTART option to \fBpcre_dfa_exec()\fP
370 \eS output details of memory get/free calls during matching
371 .\" JOIN
372 \eZ pass the PCRE_NOTEOL option to \fBpcre_exec()\fP
373 or \fBpcre_dfa_exec()\fP
374 .\" JOIN
375 \e? pass the PCRE_NO_UTF8_CHECK option to
376 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP
377 \e>dd start the match at offset dd (any number of digits);
378 .\" JOIN
379 this sets the \fIstartoffset\fP argument for \fBpcre_exec()\fP
380 or \fBpcre_dfa_exec()\fP
381 .\" JOIN
382 \e<cr> pass the PCRE_NEWLINE_CR option to \fBpcre_exec()\fP
383 or \fBpcre_dfa_exec()\fP
384 .\" JOIN
385 \e<lf> pass the PCRE_NEWLINE_LF option to \fBpcre_exec()\fP
386 or \fBpcre_dfa_exec()\fP
387 .\" JOIN
388 \e<crlf> pass the PCRE_NEWLINE_CRLF option to \fBpcre_exec()\fP
389 or \fBpcre_dfa_exec()\fP
390 .\" JOIN
391 \e<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to \fBpcre_exec()\fP
392 or \fBpcre_dfa_exec()\fP
393 .\" JOIN
394 \e<any> pass the PCRE_NEWLINE_ANY option to \fBpcre_exec()\fP
395 or \fBpcre_dfa_exec()\fP
396 .sp
397 The escapes that specify line ending sequences are literal strings, exactly as
398 shown. No more than one newline setting should be present in any data line.
399 .P
400 A backslash followed by anything else just escapes the anything else. If
401 the very last character is a backslash, it is ignored. This gives a way of
402 passing an empty line as data, since a real empty line terminates the data
403 input.
404 .P
405 If \eM is present, \fBpcretest\fP calls \fBpcre_exec()\fP several times, with
406 different values in the \fImatch_limit\fP and \fImatch_limit_recursion\fP
407 fields of the \fBpcre_extra\fP data structure, until it finds the minimum
408 numbers for each parameter that allow \fBpcre_exec()\fP to complete. The
409 \fImatch_limit\fP number is a measure of the amount of backtracking that takes
410 place, and checking it out can be instructive. For most simple matches, the
411 number is quite small, but for patterns with very large numbers of matching
412 possibilities, it can become large very quickly with increasing length of
413 subject string. The \fImatch_limit_recursion\fP number is a measure of how much
414 stack (or, if PCRE is compiled with NO_RECURSE, how much heap) memory is needed
415 to complete the match attempt.
416 .P
417 When \eO is used, the value specified may be higher or lower than the size set
418 by the \fB-O\fP command line option (or defaulted to 45); \eO applies only to
419 the call of \fBpcre_exec()\fP for the line in which it appears.
420 .P
421 If the \fB/P\fP modifier was present on the pattern, causing the POSIX wrapper
422 API to be used, the only option-setting sequences that have any effect are \eB
423 and \eZ, causing REG_NOTBOL and REG_NOTEOL, respectively, to be passed to
424 \fBregexec()\fP.
425 .P
426 The use of \ex{hh...} to represent UTF-8 characters is not dependent on the use
427 of the \fB/8\fP modifier on the pattern. It is recognized always. There may be
428 any number of hexadecimal digits inside the braces. The result is from one to
429 six bytes, encoded according to the original UTF-8 rules of RFC 2279. This
430 allows for values in the range 0 to 0x7FFFFFFF. Note that not all of those are
431 valid Unicode code points, or indeed valid UTF-8 characters according to the
432 later rules in RFC 3629.
433 .
434 .
435 .SH "THE ALTERNATIVE MATCHING FUNCTION"
436 .rs
437 .sp
438 By default, \fBpcretest\fP uses the standard PCRE matching function,
439 \fBpcre_exec()\fP to match each data line. From release 6.0, PCRE supports an
440 alternative matching function, \fBpcre_dfa_test()\fP, which operates in a
441 different way, and has some restrictions. The differences between the two
442 functions are described in the
443 .\" HREF
444 \fBpcrematching\fP
445 .\"
446 documentation.
447 .P
448 If a data line contains the \eD escape sequence, or if the command line
449 contains the \fB-dfa\fP option, the alternative matching function is called.
450 This function finds all possible matches at a given point. If, however, the \eF
451 escape sequence is present in the data line, it stops after the first match is
452 found. This is always the shortest possible match.
453 .
454 .
455 .SH "DEFAULT OUTPUT FROM PCRETEST"
456 .rs
457 .sp
458 This section describes the output when the normal matching function,
459 \fBpcre_exec()\fP, is being used.
460 .P
461 When a match succeeds, pcretest outputs the list of captured substrings that
462 \fBpcre_exec()\fP returns, starting with number 0 for the string that matched
463 the whole pattern. Otherwise, it outputs "No match" or "Partial match" followed
464 by the partially matching substring when \fBpcre_exec()\fP returns
465 PCRE_ERROR_NOMATCH or PCRE_ERROR_PARTIAL, respectively, and otherwise the PCRE
466 negative error number. Here is an example of an interactive \fBpcretest\fP run.
467 .sp
468 $ pcretest
469 PCRE version 7.0 30-Nov-2006
470 .sp
471 re> /^abc(\ed+)/
472 data> abc123
473 0: abc123
474 1: 123
475 data> xyz
476 No match
477 .sp
478 Note that unset capturing substrings that are not followed by one that is set
479 are not returned by \fBpcre_exec()\fP, and are not shown by \fBpcretest\fP. In
480 the following example, there are two capturing substrings, but when the first
481 data line is matched, the second, unset substring is not shown. An "internal"
482 unset substring is shown as "<unset>", as for the second data line.
483 .sp
484 re> /(a)|(b)/
485 data> a
486 0: a
487 1: a
488 data> b
489 0: b
490 1: <unset>
491 2: b
492 .sp
493 If the strings contain any non-printing characters, they are output as \e0x
494 escapes, or as \ex{...} escapes if the \fB/8\fP modifier was present on the
495 pattern. See below for the definition of non-printing characters. If the
496 pattern has the \fB/+\fP modifier, the output for substring 0 is followed by
497 the the rest of the subject string, identified by "0+" like this:
498 .sp
499 re> /cat/+
500 data> cataract
501 0: cat
502 0+ aract
503 .sp
504 If the pattern has the \fB/g\fP or \fB/G\fP modifier, the results of successive
505 matching attempts are output in sequence, like this:
506 .sp
507 re> /\eBi(\ew\ew)/g
508 data> Mississippi
509 0: iss
510 1: ss
511 0: iss
512 1: ss
513 0: ipp
514 1: pp
515 .sp
516 "No match" is output only if the first match attempt fails.
517 .P
518 If any of the sequences \fB\eC\fP, \fB\eG\fP, or \fB\eL\fP are present in a
519 data line that is successfully matched, the substrings extracted by the
520 convenience functions are output with C, G, or L after the string number
521 instead of a colon. This is in addition to the normal full list. The string
522 length (that is, the return from the extraction function) is given in
523 parentheses after each string for \fB\eC\fP and \fB\eG\fP.
524 .P
525 Note that whereas patterns can be continued over several lines (a plain ">"
526 prompt is used for continuations), data lines may not. However newlines can be
527 included in data by means of the \en escape (or \er, \er\en, etc., depending on
528 the newline sequence setting).
529 .
530 .
531 .
532 .SH "OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION"
533 .rs
534 .sp
535 When the alternative matching function, \fBpcre_dfa_exec()\fP, is used (by
536 means of the \eD escape sequence or the \fB-dfa\fP command line option), the
537 output consists of a list of all the matches that start at the first point in
538 the subject where there is at least one match. For example:
539 .sp
540 re> /(tang|tangerine|tan)/
541 data> yellow tangerine\eD
542 0: tangerine
543 1: tang
544 2: tan
545 .sp
546 (Using the normal matching function on this data finds only "tang".) The
547 longest matching string is always given first (and numbered zero).
548 .P
549 If \fB/g\fP is present on the pattern, the search for further matches resumes
550 at the end of the longest match. For example:
551 .sp
552 re> /(tang|tangerine|tan)/g
553 data> yellow tangerine and tangy sultana\eD
554 0: tangerine
555 1: tang
556 2: tan
557 0: tang
558 1: tan
559 0: tan
560 .sp
561 Since the matching function does not support substring capture, the escape
562 sequences that are concerned with captured substrings are not relevant.
563 .
564 .
565 .SH "RESTARTING AFTER A PARTIAL MATCH"
566 .rs
567 .sp
568 When the alternative matching function has given the PCRE_ERROR_PARTIAL return,
569 indicating that the subject partially matched the pattern, you can restart the
570 match with additional subject data by means of the \eR escape sequence. For
571 example:
572 .sp
573 re> /^\ed?\ed(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\ed\ed$/
574 data> 23ja\eP\eD
575 Partial match: 23ja
576 data> n05\eR\eD
577 0: n05
578 .sp
579 For further information about partial matching, see the
580 .\" HREF
581 \fBpcrepartial\fP
582 .\"
583 documentation.
584 .
585 .
586 .SH CALLOUTS
587 .rs
588 .sp
589 If the pattern contains any callout requests, \fBpcretest\fP's callout function
590 is called during matching. This works with both matching functions. By default,
591 the called function displays the callout number, the start and current
592 positions in the text at the callout time, and the next pattern item to be
593 tested. For example, the output
594 .sp
595 --->pqrabcdef
596 0 ^ ^ \ed
597 .sp
598 indicates that callout number 0 occurred for a match attempt starting at the
599 fourth character of the subject string, when the pointer was at the seventh
600 character of the data, and when the next pattern item was \ed. Just one
601 circumflex is output if the start and current positions are the same.
602 .P
603 Callouts numbered 255 are assumed to be automatic callouts, inserted as a
604 result of the \fB/C\fP pattern modifier. In this case, instead of showing the
605 callout number, the offset in the pattern, preceded by a plus, is output. For
606 example:
607 .sp
608 re> /\ed?[A-E]\e*/C
609 data> E*
610 --->E*
611 +0 ^ \ed?
612 +3 ^ [A-E]
613 +8 ^^ \e*
614 +10 ^ ^
615 0: E*
616 .sp
617 The callout function in \fBpcretest\fP returns zero (carry on matching) by
618 default, but you can use a \eC item in a data line (as described above) to
619 change this.
620 .P
621 Inserting callouts can be helpful when using \fBpcretest\fP to check
622 complicated regular expressions. For further information about callouts, see
623 the
624 .\" HREF
625 \fBpcrecallout\fP
626 .\"
627 documentation.
628 .
629 .
630 .
631 .SH "NON-PRINTING CHARACTERS"
632 .rs
633 .sp
634 When \fBpcretest\fP is outputting text in the compiled version of a pattern,
635 bytes other than 32-126 are always treated as non-printing characters are are
636 therefore shown as hex escapes.
637 .P
638 When \fBpcretest\fP is outputting text that is a matched part of a subject
639 string, it behaves in the same way, unless a different locale has been set for
640 the pattern (using the \fB/L\fP modifier). In this case, the \fBisprint()\fP
641 function to distinguish printing and non-printing characters.
642 .
643 .
644 .
645 .SH "SAVING AND RELOADING COMPILED PATTERNS"
646 .rs
647 .sp
648 The facilities described in this section are not available when the POSIX
649 inteface to PCRE is being used, that is, when the \fB/P\fP pattern modifier is
650 specified.
651 .P
652 When the POSIX interface is not in use, you can cause \fBpcretest\fP to write a
653 compiled pattern to a file, by following the modifiers with > and a file name.
654 For example:
655 .sp
656 /pattern/im >/some/file
657 .sp
658 See the
659 .\" HREF
660 \fBpcreprecompile\fP
661 .\"
662 documentation for a discussion about saving and re-using compiled patterns.
663 .P
664 The data that is written is binary. The first eight bytes are the length of the
665 compiled pattern data followed by the length of the optional study data, each
666 written as four bytes in big-endian order (most significant byte first). If
667 there is no study data (either the pattern was not studied, or studying did not
668 return any data), the second length is zero. The lengths are followed by an
669 exact copy of the compiled pattern. If there is additional study data, this
670 follows immediately after the compiled pattern. After writing the file,
671 \fBpcretest\fP expects to read a new pattern.
672 .P
673 A saved pattern can be reloaded into \fBpcretest\fP by specifing < and a file
674 name instead of a pattern. The name of the file must not contain a < character,
675 as otherwise \fBpcretest\fP will interpret the line as a pattern delimited by <
676 characters.
677 For example:
678 .sp
679 re> </some/file
680 Compiled regex loaded from /some/file
681 No study data
682 .sp
683 When the pattern has been loaded, \fBpcretest\fP proceeds to read data lines in
684 the usual way.
685 .P
686 You can copy a file written by \fBpcretest\fP to a different host and reload it
687 there, even if the new host has opposite endianness to the one on which the
688 pattern was compiled. For example, you can compile on an i86 machine and run on
689 a SPARC machine.
690 .P
691 File names for saving and reloading can be absolute or relative, but note that
692 the shell facility of expanding a file name that starts with a tilde (~) is not
693 available.
694 .P
695 The ability to save and reload files in \fBpcretest\fP is intended for testing
696 and experimentation. It is not intended for production use because only a
697 single pattern can be written to a file. Furthermore, there is no facility for
698 supplying custom character tables for use with a reloaded pattern. If the
699 original pattern was compiled with custom tables, an attempt to match a subject
700 string using a reloaded pattern is likely to cause \fBpcretest\fP to crash.
701 Finally, if you attempt to load a file that is not in the correct format, the
702 result is undefined.
703 .
704 .
705 .SH "SEE ALSO"
706 .rs
707 .sp
708 \fBpcre\fP(3), \fBpcreapi\fP(3), \fBpcrecallout\fP(3), \fBpcrematching\fP(3),
709 \fBpcrepartial\fP(d), \fBpcrepattern\fP(3), \fBpcreprecompile\fP(3).
710 .
711 .
712 .SH AUTHOR
713 .rs
714 .sp
715 .nf
716 Philip Hazel
717 University Computing Service
718 Cambridge CB2 3QH, England.
719 .fi
720 .
721 .
722 .SH REVISION
723 .rs
724 .sp
725 .nf
726 Last updated: 25 August 2009
727 Copyright (c) 1997-2009 University of Cambridge.
728 .fi

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