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Revision 570 - (show annotations)
Sun Nov 7 16:25:12 2010 UTC (8 years, 10 months ago) by ph10
File size: 31300 byte(s)
Clarify pcretest documentation of \xhh vs \x{hh}.
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 compile-time
169 options that do not correspond to anything in Perl:
170 .sp
171 \fB/8\fP PCRE_UTF8
172 \fB/?\fP PCRE_NO_UTF8_CHECK
173 \fB/A\fP PCRE_ANCHORED
174 \fB/C\fP PCRE_AUTO_CALLOUT
175 \fB/E\fP PCRE_DOLLAR_ENDONLY
176 \fB/f\fP PCRE_FIRSTLINE
177 \fB/J\fP PCRE_DUPNAMES
178 \fB/N\fP PCRE_NO_AUTO_CAPTURE
179 \fB/U\fP PCRE_UNGREEDY
180 \fB/W\fP PCRE_UCP
181 \fB/X\fP PCRE_EXTRA
182 \fB/<JS>\fP PCRE_JAVASCRIPT_COMPAT
183 \fB/<cr>\fP PCRE_NEWLINE_CR
184 \fB/<lf>\fP PCRE_NEWLINE_LF
185 \fB/<crlf>\fP PCRE_NEWLINE_CRLF
186 \fB/<anycrlf>\fP PCRE_NEWLINE_ANYCRLF
187 \fB/<any>\fP PCRE_NEWLINE_ANY
188 \fB/<bsr_anycrlf>\fP PCRE_BSR_ANYCRLF
189 \fB/<bsr_unicode>\fP PCRE_BSR_UNICODE
190 .sp
191 The modifiers that are enclosed in angle brackets are literal strings as shown,
192 including the angle brackets, but the letters can be in either case. This
193 example sets multiline matching with CRLF as the line ending sequence:
194 .sp
195 /^abc/m<crlf>
196 .sp
197 As well as turning on the PCRE_UTF8 option, the \fB/8\fP modifier also causes
198 any non-printing characters in output strings to be printed using the
199 \ex{hh...} notation if they are valid UTF-8 sequences. Full details of the PCRE
200 options are given in the
201 .\" HREF
202 \fBpcreapi\fP
203 .\"
204 documentation.
205 .
206 .
207 .SS "Finding all matches in a string"
208 .rs
209 .sp
210 Searching for all possible matches within each subject string can be requested
211 by the \fB/g\fP or \fB/G\fP modifier. After finding a match, PCRE is called
212 again to search the remainder of the subject string. The difference between
213 \fB/g\fP and \fB/G\fP is that the former uses the \fIstartoffset\fP argument to
214 \fBpcre_exec()\fP to start searching at a new point within the entire string
215 (which is in effect what Perl does), whereas the latter passes over a shortened
216 substring. This makes a difference to the matching process if the pattern
217 begins with a lookbehind assertion (including \eb or \eB).
218 .P
219 If any call to \fBpcre_exec()\fP in a \fB/g\fP or \fB/G\fP sequence matches an
220 empty string, the next call is done with the PCRE_NOTEMPTY_ATSTART and
221 PCRE_ANCHORED flags set in order to search for another, non-empty, match at the
222 same point. If this second match fails, the start offset is advanced, and the
223 normal match is retried. This imitates the way Perl handles such cases when
224 using the \fB/g\fP modifier or the \fBsplit()\fP function. Normally, the start
225 offset is advanced by one character, but if the newline convention recognizes
226 CRLF as a newline, and the current character is CR followed by LF, an advance
227 of two is used.
228 .
229 .
230 .SS "Other modifiers"
231 .rs
232 .sp
233 There are yet more modifiers for controlling the way \fBpcretest\fP
234 operates.
235 .P
236 The \fB/+\fP modifier requests that as well as outputting the substring that
237 matched the entire pattern, pcretest should in addition output the remainder of
238 the subject string. This is useful for tests where the subject contains
239 multiple copies of the same substring.
240 .P
241 The \fB/B\fP modifier is a debugging feature. It requests that \fBpcretest\fP
242 output a representation of the compiled byte code after compilation. Normally
243 this information contains length and offset values; however, if \fB/Z\fP is
244 also present, this data is replaced by spaces. This is a special feature for
245 use in the automatic test scripts; it ensures that the same output is generated
246 for different internal link sizes.
247 .P
248 The \fB/D\fP modifier is a PCRE debugging feature, and is equivalent to
249 \fB/BI\fP, that is, both the \fB/B\fP and the \fB/I\fP modifiers.
250 .P
251 The \fB/F\fP modifier causes \fBpcretest\fP to flip the byte order of the
252 fields in the compiled pattern that contain 2-byte and 4-byte numbers. This
253 facility is for testing the feature in PCRE that allows it to execute patterns
254 that were compiled on a host with a different endianness. This feature is not
255 available when the POSIX interface to PCRE is being used, that is, when the
256 \fB/P\fP pattern modifier is specified. See also the section about saving and
257 reloading compiled patterns below.
258 .P
259 The \fB/I\fP modifier requests that \fBpcretest\fP output information about the
260 compiled pattern (whether it is anchored, has a fixed first character, and
261 so on). It does this by calling \fBpcre_fullinfo()\fP after compiling a
262 pattern. If the pattern is studied, the results of that are also output.
263 .P
264 The \fB/K\fP modifier requests \fBpcretest\fP to show names from backtracking
265 control verbs that are returned from calls to \fBpcre_exec()\fP. It causes
266 \fBpcretest\fP to create a \fBpcre_extra\fP block if one has not already been
267 created by a call to \fBpcre_study()\fP, and to set the PCRE_EXTRA_MARK flag
268 and the \fBmark\fP field within it, every time that \fBpcre_exec()\fP is
269 called. If the variable that the \fBmark\fP field points to is non-NULL for a
270 match, non-match, or partial match, \fBpcretest\fP prints the string to which
271 it points. For a match, this is shown on a line by itself, tagged with "MK:".
272 For a non-match it is added to the message.
273 .P
274 The \fB/L\fP modifier must be followed directly by the name of a locale, for
275 example,
276 .sp
277 /pattern/Lfr_FR
278 .sp
279 For this reason, it must be the last modifier. The given locale is set,
280 \fBpcre_maketables()\fP is called to build a set of character tables for the
281 locale, and this is then passed to \fBpcre_compile()\fP when compiling the
282 regular expression. Without an \fB/L\fP (or \fB/T\fP) modifier, NULL is passed
283 as the tables pointer; that is, \fB/L\fP applies only to the expression on
284 which it appears.
285 .P
286 The \fB/M\fP modifier causes the size of memory block used to hold the compiled
287 pattern to be output.
288 .P
289 The \fB/S\fP modifier causes \fBpcre_study()\fP to be called after the
290 expression has been compiled, and the results used when the expression is
291 matched.
292 .P
293 The \fB/T\fP modifier must be followed by a single digit. It causes a specific
294 set of built-in character tables to be passed to \fBpcre_compile()\fP. It is
295 used in the standard PCRE tests to check behaviour with different character
296 tables. The digit specifies the tables as follows:
297 .sp
298 0 the default ASCII tables, as distributed in
299 pcre_chartables.c.dist
300 1 a set of tables defining ISO 8859 characters
301 .sp
302 In table 1, some characters whose codes are greater than 128 are identified as
303 letters, digits, spaces, etc.
304 .
305 .
306 .SS "Using the POSIX wrapper API"
307 .rs
308 .sp
309 The \fB/P\fP modifier causes \fBpcretest\fP to call PCRE via the POSIX wrapper
310 API rather than its native API. When \fB/P\fP is set, the following modifiers
311 set options for the \fBregcomp()\fP function:
312 .sp
313 /i REG_ICASE
314 /m REG_NEWLINE
315 /N REG_NOSUB
316 /s REG_DOTALL )
317 /U REG_UNGREEDY ) These options are not part of
318 /W REG_UCP ) the POSIX standard
319 /8 REG_UTF8 )
320 .sp
321 The \fB/+\fP modifier works as described above. All other modifiers are
322 ignored.
323 .
324 .
325 .SH "DATA LINES"
326 .rs
327 .sp
328 Before each data line is passed to \fBpcre_exec()\fP, leading and trailing
329 whitespace is removed, and it is then scanned for \e escapes. Some of these are
330 pretty esoteric features, intended for checking out some of the more
331 complicated features of PCRE. If you are just testing "ordinary" regular
332 expressions, you probably don't need any of these. The following escapes are
333 recognized:
334 .sp
335 \ea alarm (BEL, \ex07)
336 \eb backspace (\ex08)
337 \ee escape (\ex27)
338 \ef formfeed (\ex0c)
339 \en newline (\ex0a)
340 .\" JOIN
341 \eqdd set the PCRE_MATCH_LIMIT limit to dd
342 (any number of digits)
343 \er carriage return (\ex0d)
344 \et tab (\ex09)
345 \ev vertical tab (\ex0b)
346 \ennn octal character (up to 3 octal digits)
347 always a byte unless > 255 in UTF-8 mode
348 \exhh hexadecimal byte (up to 2 hex digits)
349 .\" JOIN
350 \ex{hh...} hexadecimal character, any number of digits
351 in UTF-8 mode
352 .\" JOIN
353 \eA pass the PCRE_ANCHORED option to \fBpcre_exec()\fP
354 or \fBpcre_dfa_exec()\fP
355 .\" JOIN
356 \eB pass the PCRE_NOTBOL option to \fBpcre_exec()\fP
357 or \fBpcre_dfa_exec()\fP
358 .\" JOIN
359 \eCdd call pcre_copy_substring() for substring dd
360 after a successful match (number less than 32)
361 .\" JOIN
362 \eCname call pcre_copy_named_substring() for substring
363 "name" after a successful match (name termin-
364 ated by next non alphanumeric character)
365 .\" JOIN
366 \eC+ show the current captured substrings at callout
367 time
368 \eC- do not supply a callout function
369 .\" JOIN
370 \eC!n return 1 instead of 0 when callout number n is
371 reached
372 .\" JOIN
373 \eC!n!m return 1 instead of 0 when callout number n is
374 reached for the nth time
375 .\" JOIN
376 \eC*n pass the number n (may be negative) as callout
377 data; this is used as the callout return value
378 \eD use the \fBpcre_dfa_exec()\fP match function
379 \eF only shortest match for \fBpcre_dfa_exec()\fP
380 .\" JOIN
381 \eGdd call pcre_get_substring() for substring dd
382 after a successful match (number less than 32)
383 .\" JOIN
384 \eGname call pcre_get_named_substring() for substring
385 "name" after a successful match (name termin-
386 ated by next non-alphanumeric character)
387 .\" JOIN
388 \eL call pcre_get_substringlist() after a
389 successful match
390 .\" JOIN
391 \eM discover the minimum MATCH_LIMIT and
392 MATCH_LIMIT_RECURSION settings
393 .\" JOIN
394 \eN pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fP
395 or \fBpcre_dfa_exec()\fP; if used twice, pass the
396 PCRE_NOTEMPTY_ATSTART option
397 .\" JOIN
398 \eOdd set the size of the output vector passed to
399 \fBpcre_exec()\fP to dd (any number of digits)
400 .\" JOIN
401 \eP pass the PCRE_PARTIAL_SOFT option to \fBpcre_exec()\fP
402 or \fBpcre_dfa_exec()\fP; if used twice, pass the
403 PCRE_PARTIAL_HARD option
404 .\" JOIN
405 \eQdd set the PCRE_MATCH_LIMIT_RECURSION limit to dd
406 (any number of digits)
407 \eR pass the PCRE_DFA_RESTART option to \fBpcre_dfa_exec()\fP
408 \eS output details of memory get/free calls during matching
409 .\" JOIN
410 \eY pass the PCRE_NO_START_OPTIMIZE option to \fBpcre_exec()\fP
411 or \fBpcre_dfa_exec()\fP
412 .\" JOIN
413 \eZ pass the PCRE_NOTEOL option to \fBpcre_exec()\fP
414 or \fBpcre_dfa_exec()\fP
415 .\" JOIN
416 \e? pass the PCRE_NO_UTF8_CHECK option to
417 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP
418 .\" JOIN
419 \e>dd start the match at offset dd (optional "-"; then
420 any number of digits); this sets the \fIstartoffset\fP
421 argument for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP
422 .\" JOIN
423 \e<cr> pass the PCRE_NEWLINE_CR option to \fBpcre_exec()\fP
424 or \fBpcre_dfa_exec()\fP
425 .\" JOIN
426 \e<lf> pass the PCRE_NEWLINE_LF option to \fBpcre_exec()\fP
427 or \fBpcre_dfa_exec()\fP
428 .\" JOIN
429 \e<crlf> pass the PCRE_NEWLINE_CRLF option to \fBpcre_exec()\fP
430 or \fBpcre_dfa_exec()\fP
431 .\" JOIN
432 \e<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to \fBpcre_exec()\fP
433 or \fBpcre_dfa_exec()\fP
434 .\" JOIN
435 \e<any> pass the PCRE_NEWLINE_ANY option to \fBpcre_exec()\fP
436 or \fBpcre_dfa_exec()\fP
437 .sp
438 Note that \exhh always specifies one byte, even in UTF-8 mode; this makes it
439 possible to construct invalid UTF-8 sequences for testing purposes. On the
440 other hand, \ex{hh} is interpreted as a UTF-8 character in UTF-8 mode,
441 generating more than one byte if the value is greater than 127. When not in
442 UTF-8 mode, it generates one byte for values less than 256, and causes an error
443 for greater values.
444 .P
445 The escapes that specify line ending sequences are literal strings, exactly as
446 shown. No more than one newline setting should be present in any data line.
447 .P
448 A backslash followed by anything else just escapes the anything else. If
449 the very last character is a backslash, it is ignored. This gives a way of
450 passing an empty line as data, since a real empty line terminates the data
451 input.
452 .P
453 If \eM is present, \fBpcretest\fP calls \fBpcre_exec()\fP several times, with
454 different values in the \fImatch_limit\fP and \fImatch_limit_recursion\fP
455 fields of the \fBpcre_extra\fP data structure, until it finds the minimum
456 numbers for each parameter that allow \fBpcre_exec()\fP to complete. The
457 \fImatch_limit\fP number is a measure of the amount of backtracking that takes
458 place, and checking it out can be instructive. For most simple matches, the
459 number is quite small, but for patterns with very large numbers of matching
460 possibilities, it can become large very quickly with increasing length of
461 subject string. The \fImatch_limit_recursion\fP number is a measure of how much
462 stack (or, if PCRE is compiled with NO_RECURSE, how much heap) memory is needed
463 to complete the match attempt.
464 .P
465 When \eO is used, the value specified may be higher or lower than the size set
466 by the \fB-O\fP command line option (or defaulted to 45); \eO applies only to
467 the call of \fBpcre_exec()\fP for the line in which it appears.
468 .P
469 If the \fB/P\fP modifier was present on the pattern, causing the POSIX wrapper
470 API to be used, the only option-setting sequences that have any effect are \eB,
471 \eN, and \eZ, causing REG_NOTBOL, REG_NOTEMPTY, and REG_NOTEOL, respectively,
472 to be passed to \fBregexec()\fP.
473 .P
474 The use of \ex{hh...} to represent UTF-8 characters is not dependent on the use
475 of the \fB/8\fP modifier on the pattern. It is recognized always. There may be
476 any number of hexadecimal digits inside the braces. The result is from one to
477 six bytes, encoded according to the original UTF-8 rules of RFC 2279. This
478 allows for values in the range 0 to 0x7FFFFFFF. Note that not all of those are
479 valid Unicode code points, or indeed valid UTF-8 characters according to the
480 later rules in RFC 3629.
481 .
482 .
483 .SH "THE ALTERNATIVE MATCHING FUNCTION"
484 .rs
485 .sp
486 By default, \fBpcretest\fP uses the standard PCRE matching function,
487 \fBpcre_exec()\fP to match each data line. From release 6.0, PCRE supports an
488 alternative matching function, \fBpcre_dfa_test()\fP, which operates in a
489 different way, and has some restrictions. The differences between the two
490 functions are described in the
491 .\" HREF
492 \fBpcrematching\fP
493 .\"
494 documentation.
495 .P
496 If a data line contains the \eD escape sequence, or if the command line
497 contains the \fB-dfa\fP option, the alternative matching function is called.
498 This function finds all possible matches at a given point. If, however, the \eF
499 escape sequence is present in the data line, it stops after the first match is
500 found. This is always the shortest possible match.
501 .
502 .
503 .SH "DEFAULT OUTPUT FROM PCRETEST"
504 .rs
505 .sp
506 This section describes the output when the normal matching function,
507 \fBpcre_exec()\fP, is being used.
508 .P
509 When a match succeeds, pcretest outputs the list of captured substrings that
510 \fBpcre_exec()\fP returns, starting with number 0 for the string that matched
511 the whole pattern. Otherwise, it outputs "No match" when the return is
512 PCRE_ERROR_NOMATCH, and "Partial match:" followed by the partially matching
513 substring when \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL. (Note that this is
514 the entire substring that was inspected during the partial match; it may
515 include characters before the actual match start if a lookbehind assertion,
516 \eK, \eb, or \eB was involved.) For any other returns, it outputs the PCRE
517 negative error number. Here is an example of an interactive \fBpcretest\fP run.
518 .sp
519 $ pcretest
520 PCRE version 7.0 30-Nov-2006
521 .sp
522 re> /^abc(\ed+)/
523 data> abc123
524 0: abc123
525 1: 123
526 data> xyz
527 No match
528 .sp
529 Note that unset capturing substrings that are not followed by one that is set
530 are not returned by \fBpcre_exec()\fP, and are not shown by \fBpcretest\fP. In
531 the following example, there are two capturing substrings, but when the first
532 data line is matched, the second, unset substring is not shown. An "internal"
533 unset substring is shown as "<unset>", as for the second data line.
534 .sp
535 re> /(a)|(b)/
536 data> a
537 0: a
538 1: a
539 data> b
540 0: b
541 1: <unset>
542 2: b
543 .sp
544 If the strings contain any non-printing characters, they are output as \e0x
545 escapes, or as \ex{...} escapes if the \fB/8\fP modifier was present on the
546 pattern. See below for the definition of non-printing characters. If the
547 pattern has the \fB/+\fP modifier, the output for substring 0 is followed by
548 the the rest of the subject string, identified by "0+" like this:
549 .sp
550 re> /cat/+
551 data> cataract
552 0: cat
553 0+ aract
554 .sp
555 If the pattern has the \fB/g\fP or \fB/G\fP modifier, the results of successive
556 matching attempts are output in sequence, like this:
557 .sp
558 re> /\eBi(\ew\ew)/g
559 data> Mississippi
560 0: iss
561 1: ss
562 0: iss
563 1: ss
564 0: ipp
565 1: pp
566 .sp
567 "No match" is output only if the first match attempt fails.
568 .P
569 If any of the sequences \fB\eC\fP, \fB\eG\fP, or \fB\eL\fP are present in a
570 data line that is successfully matched, the substrings extracted by the
571 convenience functions are output with C, G, or L after the string number
572 instead of a colon. This is in addition to the normal full list. The string
573 length (that is, the return from the extraction function) is given in
574 parentheses after each string for \fB\eC\fP and \fB\eG\fP.
575 .P
576 Note that whereas patterns can be continued over several lines (a plain ">"
577 prompt is used for continuations), data lines may not. However newlines can be
578 included in data by means of the \en escape (or \er, \er\en, etc., depending on
579 the newline sequence setting).
580 .
581 .
582 .
583 .SH "OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION"
584 .rs
585 .sp
586 When the alternative matching function, \fBpcre_dfa_exec()\fP, is used (by
587 means of the \eD escape sequence or the \fB-dfa\fP command line option), the
588 output consists of a list of all the matches that start at the first point in
589 the subject where there is at least one match. For example:
590 .sp
591 re> /(tang|tangerine|tan)/
592 data> yellow tangerine\eD
593 0: tangerine
594 1: tang
595 2: tan
596 .sp
597 (Using the normal matching function on this data finds only "tang".) The
598 longest matching string is always given first (and numbered zero). After a
599 PCRE_ERROR_PARTIAL return, the output is "Partial match:", followed by the
600 partially matching substring. (Note that this is the entire substring that was
601 inspected during the partial match; it may include characters before the actual
602 match start if a lookbehind assertion, \eK, \eb, or \eB was involved.)
603 .P
604 If \fB/g\fP is present on the pattern, the search for further matches resumes
605 at the end of the longest match. For example:
606 .sp
607 re> /(tang|tangerine|tan)/g
608 data> yellow tangerine and tangy sultana\eD
609 0: tangerine
610 1: tang
611 2: tan
612 0: tang
613 1: tan
614 0: tan
615 .sp
616 Since the matching function does not support substring capture, the escape
617 sequences that are concerned with captured substrings are not relevant.
618 .
619 .
620 .SH "RESTARTING AFTER A PARTIAL MATCH"
621 .rs
622 .sp
623 When the alternative matching function has given the PCRE_ERROR_PARTIAL return,
624 indicating that the subject partially matched the pattern, you can restart the
625 match with additional subject data by means of the \eR escape sequence. For
626 example:
627 .sp
628 re> /^\ed?\ed(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\ed\ed$/
629 data> 23ja\eP\eD
630 Partial match: 23ja
631 data> n05\eR\eD
632 0: n05
633 .sp
634 For further information about partial matching, see the
635 .\" HREF
636 \fBpcrepartial\fP
637 .\"
638 documentation.
639 .
640 .
641 .SH CALLOUTS
642 .rs
643 .sp
644 If the pattern contains any callout requests, \fBpcretest\fP's callout function
645 is called during matching. This works with both matching functions. By default,
646 the called function displays the callout number, the start and current
647 positions in the text at the callout time, and the next pattern item to be
648 tested. For example, the output
649 .sp
650 --->pqrabcdef
651 0 ^ ^ \ed
652 .sp
653 indicates that callout number 0 occurred for a match attempt starting at the
654 fourth character of the subject string, when the pointer was at the seventh
655 character of the data, and when the next pattern item was \ed. Just one
656 circumflex is output if the start and current positions are the same.
657 .P
658 Callouts numbered 255 are assumed to be automatic callouts, inserted as a
659 result of the \fB/C\fP pattern modifier. In this case, instead of showing the
660 callout number, the offset in the pattern, preceded by a plus, is output. For
661 example:
662 .sp
663 re> /\ed?[A-E]\e*/C
664 data> E*
665 --->E*
666 +0 ^ \ed?
667 +3 ^ [A-E]
668 +8 ^^ \e*
669 +10 ^ ^
670 0: E*
671 .sp
672 The callout function in \fBpcretest\fP returns zero (carry on matching) by
673 default, but you can use a \eC item in a data line (as described above) to
674 change this.
675 .P
676 Inserting callouts can be helpful when using \fBpcretest\fP to check
677 complicated regular expressions. For further information about callouts, see
678 the
679 .\" HREF
680 \fBpcrecallout\fP
681 .\"
682 documentation.
683 .
684 .
685 .
686 .SH "NON-PRINTING CHARACTERS"
687 .rs
688 .sp
689 When \fBpcretest\fP is outputting text in the compiled version of a pattern,
690 bytes other than 32-126 are always treated as non-printing characters are are
691 therefore shown as hex escapes.
692 .P
693 When \fBpcretest\fP is outputting text that is a matched part of a subject
694 string, it behaves in the same way, unless a different locale has been set for
695 the pattern (using the \fB/L\fP modifier). In this case, the \fBisprint()\fP
696 function to distinguish printing and non-printing characters.
697 .
698 .
699 .
700 .SH "SAVING AND RELOADING COMPILED PATTERNS"
701 .rs
702 .sp
703 The facilities described in this section are not available when the POSIX
704 inteface to PCRE is being used, that is, when the \fB/P\fP pattern modifier is
705 specified.
706 .P
707 When the POSIX interface is not in use, you can cause \fBpcretest\fP to write a
708 compiled pattern to a file, by following the modifiers with > and a file name.
709 For example:
710 .sp
711 /pattern/im >/some/file
712 .sp
713 See the
714 .\" HREF
715 \fBpcreprecompile\fP
716 .\"
717 documentation for a discussion about saving and re-using compiled patterns.
718 .P
719 The data that is written is binary. The first eight bytes are the length of the
720 compiled pattern data followed by the length of the optional study data, each
721 written as four bytes in big-endian order (most significant byte first). If
722 there is no study data (either the pattern was not studied, or studying did not
723 return any data), the second length is zero. The lengths are followed by an
724 exact copy of the compiled pattern. If there is additional study data, this
725 follows immediately after the compiled pattern. After writing the file,
726 \fBpcretest\fP expects to read a new pattern.
727 .P
728 A saved pattern can be reloaded into \fBpcretest\fP by specifing < and a file
729 name instead of a pattern. The name of the file must not contain a < character,
730 as otherwise \fBpcretest\fP will interpret the line as a pattern delimited by <
731 characters.
732 For example:
733 .sp
734 re> </some/file
735 Compiled regex loaded from /some/file
736 No study data
737 .sp
738 When the pattern has been loaded, \fBpcretest\fP proceeds to read data lines in
739 the usual way.
740 .P
741 You can copy a file written by \fBpcretest\fP to a different host and reload it
742 there, even if the new host has opposite endianness to the one on which the
743 pattern was compiled. For example, you can compile on an i86 machine and run on
744 a SPARC machine.
745 .P
746 File names for saving and reloading can be absolute or relative, but note that
747 the shell facility of expanding a file name that starts with a tilde (~) is not
748 available.
749 .P
750 The ability to save and reload files in \fBpcretest\fP is intended for testing
751 and experimentation. It is not intended for production use because only a
752 single pattern can be written to a file. Furthermore, there is no facility for
753 supplying custom character tables for use with a reloaded pattern. If the
754 original pattern was compiled with custom tables, an attempt to match a subject
755 string using a reloaded pattern is likely to cause \fBpcretest\fP to crash.
756 Finally, if you attempt to load a file that is not in the correct format, the
757 result is undefined.
758 .
759 .
760 .SH "SEE ALSO"
761 .rs
762 .sp
763 \fBpcre\fP(3), \fBpcreapi\fP(3), \fBpcrecallout\fP(3), \fBpcrematching\fP(3),
764 \fBpcrepartial\fP(d), \fBpcrepattern\fP(3), \fBpcreprecompile\fP(3).
765 .
766 .
767 .SH AUTHOR
768 .rs
769 .sp
770 .nf
771 Philip Hazel
772 University Computing Service
773 Cambridge CB2 3QH, England.
774 .fi
775 .
776 .
777 .SH REVISION
778 .rs
779 .sp
780 .nf
781 Last updated: 07 November 2010
782 Copyright (c) 1997-2010 University of Cambridge.
783 .fi

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