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1  The pcretest program  PCRETEST(1)                                                        PCRETEST(1)
 --------------------  
2    
 This program is intended for testing PCRE, but it can also be used for  
 experimenting with regular expressions.  
3    
 If it is given two filename arguments, it reads from the first and writes to  
 the second. If it is given only one filename argument, it reads from that file  
 and writes to stdout. Otherwise, it reads from stdin and writes to stdout, and  
 prompts for each line of input, using "re>" to prompt for regular expressions,  
 and "data>" to prompt for data lines.  
   
 The program handles any number of sets of input on a single input file. Each  
 set starts with a regular expression, and continues with any number of data  
 lines to be matched against the pattern. An empty line signals the end of the  
 data lines, at which point a new regular expression is read. The regular  
 expressions are given enclosed in any non-alphameric delimiters other than  
 backslash, for example  
   
   /(a|bc)x+yz/  
   
 White space before the initial delimiter is ignored. A regular expression may  
 be continued over several input lines, in which case the newline characters are  
 included within it. See the test input files in the testdata directory for many  
 examples. It is possible to include the delimiter within the pattern by  
 escaping it, for example  
   
   /abc\/def/  
   
 If you do so, the escape and the delimiter form part of the pattern, but since  
 delimiters are always non-alphameric, this does not affect its interpretation.  
 If the terminating delimiter is immediately followed by a backslash, for  
 example,  
   
   /abc/\  
   
 then a backslash is added to the end of the pattern. This is done to provide a  
 way of testing the error condition that arises if a pattern finishes with a  
 backslash, because  
   
   /abc\/  
   
 is interpreted as the first line of a pattern that starts with "abc/", causing  
 pcretest to read the next line as a continuation of the regular expression.  
   
 The pattern may be followed by i, m, s, or x to set the PCRE_CASELESS,  
 PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. For  
 example:  
   
   /caseless/i  
   
 These modifier letters have the same effect as they do in Perl. There are  
 others which set PCRE options that do not correspond to anything in Perl: /A,  
 /E, and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.  
   
 Searching for all possible matches within each subject string can be requested  
 by the /g or /G modifier. After finding a match, PCRE is called again to search  
 the remainder of the subject string. The difference between /g and /G is that  
 the former uses the startoffset argument to pcre_exec() to start searching at  
 a new point within the entire string (which is in effect what Perl does),  
 whereas the latter passes over a shortened substring. This makes a difference  
 to the matching process if the pattern begins with a lookbehind assertion  
 (including \b or \B).  
   
 If any call to pcre_exec() in a /g or /G sequence matches an empty string, the  
 next call is done with the PCRE_NOTEMPTY flag set so that it cannot match an  
 empty string again at the same point. If however, this second match fails, the  
 start offset is advanced by one, and the match is retried. This imitates the  
 way Perl handles such cases when using the /g modifier or the split() function.  
   
 There are a number of other modifiers for controlling the way pcretest  
 operates.  
   
 The /+ modifier requests that as well as outputting the substring that matched  
 the entire pattern, pcretest should in addition output the remainder of the  
 subject string. This is useful for tests where the subject contains multiple  
 copies of the same substring.  
   
 The /L modifier must be followed directly by the name of a locale, for example,  
   
   /pattern/Lfr  
   
 For this reason, it must be the last modifier letter. The given locale is set,  
 pcre_maketables() is called to build a set of character tables for the locale,  
 and this is then passed to pcre_compile() when compiling the regular  
 expression. Without an /L modifier, NULL is passed as the tables pointer; that  
 is, /L applies only to the expression on which it appears.  
   
 The /I modifier requests that pcretest output information about the compiled  
 expression (whether it is anchored, has a fixed first character, and so on). It  
 does this by calling pcre_fullinfo() after compiling an expression, and  
 outputting the information it gets back. If the pattern is studied, the results  
 of that are also output.  
   
 The /D modifier is a PCRE debugging feature, which also assumes /I. It causes  
 the internal form of compiled regular expressions to be output after  
 compilation.  
   
 The /S modifier causes pcre_study() to be called after the expression has been  
 compiled, and the results used when the expression is matched.  
   
 The /M modifier causes the size of memory block used to hold the compiled  
 pattern to be output.  
   
 Finally, the /P modifier causes pcretest to call PCRE via the POSIX wrapper API  
 rather than its native API. When this is done, all other modifiers except /i,  
 /m, and /+ are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is  
 set if /m is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always,  
 and PCRE_DOTALL unless REG_NEWLINE is set.  
   
 Before each data line is passed to pcre_exec(), leading and trailing whitespace  
 is removed, and it is then scanned for \ escapes. The following are recognized:  
   
   \a     alarm (= BEL)  
   \b     backspace  
   \e     escape  
   \f     formfeed  
   \n     newline  
   \r     carriage return  
   \t     tab  
   \v     vertical tab  
   \nnn   octal character (up to 3 octal digits)  
   \xhh   hexadecimal character (up to 2 hex digits)  
   
   \A     pass the PCRE_ANCHORED option to pcre_exec()  
   \B     pass the PCRE_NOTBOL option to pcre_exec()  
   \Cdd   call pcre_copy_substring() for substring dd after a successful match  
            (any decimal number less than 32)  
   \Gdd   call pcre_get_substring() for substring dd after a successful match  
            (any decimal number less than 32)  
   \L     call pcre_get_substringlist() after a successful match  
   \N     pass the PCRE_NOTEMPTY option to pcre_exec()  
   \Odd   set the size of the output vector passed to pcre_exec() to dd  
            (any number of decimal digits)  
   \Z     pass the PCRE_NOTEOL option to pcre_exec()  
   
 A backslash followed by anything else just escapes the anything else. If the  
 very last character is a backslash, it is ignored. This gives a way of passing  
 an empty line as data, since a real empty line terminates the data input.  
   
 If /P was present on the regex, causing the POSIX wrapper API to be used, only  
 \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to  
 regexec() respectively.  
   
 When a match succeeds, pcretest outputs the list of captured substrings that  
 pcre_exec() returns, starting with number 0 for the string that matched the  
 whole pattern. Here is an example of an interactive pcretest run.  
   
   $ pcretest  
   PCRE version 2.06 08-Jun-1999  
   
     re> /^abc(\d+)/  
   data> abc123  
    0: abc123  
    1: 123  
   data> xyz  
   No match  
   
 If the strings contain any non-printing characters, they are output as \0x  
 escapes. If the pattern has the /+ modifier, then the output for substring 0 is  
 followed by the the rest of the subject string, identified by "0+" like this:  
   
     re> /cat/+  
   data> cataract  
    0: cat  
    0+ aract  
   
 If the pattern has the /g or /G modifier, the results of successive matching  
 attempts are output in sequence, like this:  
   
     re> /\Bi(\w\w)/g  
   data> Mississippi  
    0: iss  
    1: ss  
    0: iss  
    1: ss  
    0: ipp  
    1: pp  
   
 "No match" is output only if the first match attempt fails.  
   
 If any of \C, \G, or \L are present in a data line that is successfully  
 matched, the substrings extracted by the convenience functions are output with  
 C, G, or L after the string number instead of a colon. This is in addition to  
 the normal full list. The string length (that is, the return from the  
 extraction function) is given in parentheses after each string for \C and \G.  
   
 Note that while patterns can be continued over several lines (a plain ">"  
 prompt is used for continuations), data lines may not. However newlines can be  
 included in data by means of the \n escape.  
   
 If the -p option is given to pcretest, it is equivalent to adding /P to each  
 regular expression: the POSIX wrapper API is used to call PCRE. None of the  
 following flags has any effect in this case.  
   
 If the option -d is given to pcretest, it is equivalent to adding /D to each  
 regular expression: the internal form is output after compilation.  
   
 If the option -i is given to pcretest, it is equivalent to adding /I to each  
 regular expression: information about the compiled pattern is given after  
 compilation.  
   
 If the option -m is given to pcretest, it outputs the size of each compiled  
 pattern after it has been compiled. It is equivalent to adding /M to each  
 regular expression. For compatibility with earlier versions of pcretest, -s is  
 a synonym for -m.  
   
 If the -t option is given, each compile, study, and match is run 20000 times  
 while being timed, and the resulting time per compile or match is output in  
 milliseconds. Do not set -t with -s, because you will then get the size output  
 20000 times and the timing will be distorted. If you want to change the number  
 of repetitions used for timing, edit the definition of LOOPREPEAT at the top of  
 pcretest.c  
4    
5  Philip Hazel <ph10@cam.ac.uk>  NAME
6  January 2000         pcretest - a program for testing Perl-compatible regular expressions.
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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