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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  
4    
5    /abc\/  NAME
6           pcretest - a program for testing Perl-compatible regular expressions.
7    
8  is interpreted as the first line of a pattern that starts with "abc/", causing  SYNOPSIS
9  pcretest to read the next line as a continuation of the regular expression.  
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  PATTERN MODIFIERS
 -----------------  
110    
111  The pattern may be followed by i, m, s, or x to set the PCRE_CASELESS,         A pattern may be followed by any number of modifiers, which are  mostly
112  PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. For         single  characters.  Following  Perl usage, these are referred to below
113  example:         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    /caseless/i         modifiers. Whitespace may appear between the  final  pattern  delimiter
116           and the first modifier, and between the modifiers themselves.
117  These modifier letters have the same effect as they do in Perl. There are  
118  others which set PCRE options that do not correspond to anything in Perl: /A,         The /i, /m, /s, and /x modifiers set the PCRE_CASELESS, PCRE_MULTILINE,
119  /E, and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.         PCRE_DOTALL, or PCRE_EXTENDED  options,  respectively,  when  pcre_com-
120           pile()  is  called. These four modifier letters have the same effect as
121  Searching for all possible matches within each subject string can be requested         they do in Perl. For example:
122  by the /g or /G modifier. After finding a match, PCRE is called again to search  
123  the remainder of the subject string. The difference between /g and /G is that           /caseless/i
124  the former uses the startoffset argument to pcre_exec() to start searching at  
125  a new point within the entire string (which is in effect what Perl does),         The following table shows additional modifiers for setting PCRE options
126  whereas the latter passes over a shortened substring. This makes a difference         that do not correspond to anything in Perl:
127  to the matching process if the pattern begins with a lookbehind assertion  
128  (including \b or \B).           /A    PCRE_ANCHORED
129             /C    PCRE_AUTO_CALLOUT
130  If any call to pcre_exec() in a /g or /G sequence matches an empty string, the           /E    PCRE_DOLLAR_ENDONLY
131  next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED flags set in order           /f    PCRE_FIRSTLINE
132  to search for another, non-empty, match at the same point. If this second match           /N    PCRE_NO_AUTO_CAPTURE
133  fails, the start offset is advanced by one, and the normal match is retried.           /U    PCRE_UNGREEDY
134  This imitates the way Perl handles such cases when using the /g modifier or the           /X    PCRE_EXTRA
135  split() function.  
136           Searching  for  all  possible matches within each subject string can be
137  There are a number of other modifiers for controlling the way pcretest         requested by the /g or /G modifier. After  finding  a  match,  PCRE  is
138  operates.         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  The /+ modifier requests that as well as outputting the substring that matched         to  pcre_exec()  to  start  searching  at a new point within the entire
141  the entire pattern, pcretest should in addition output the remainder of the         string (which is in effect what Perl does), whereas the  latter  passes
142  subject string. This is useful for tests where the subject contains multiple         over  a  shortened  substring.  This makes a difference to the matching
143  copies of the same substring.         process if the pattern begins with a lookbehind assertion (including \b
144           or \B).
145  The /L modifier must be followed directly by the name of a locale, for example,  
146           If  any  call  to  pcre_exec()  in a /g or /G sequence matches an empty
147    /pattern/Lfr         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  For this reason, it must be the last modifier letter. The given locale is set,         point.  If this second match fails, the start  offset  is  advanced  by
150  pcre_maketables() is called to build a set of character tables for the locale,         one,  and  the normal match is retried. This imitates the way Perl han-
151  and this is then passed to pcre_compile() when compiling the regular         dles such cases when using the /g modifier or the split() function.
152  expression. Without an /L modifier, NULL is passed as the tables pointer; that  
153  is, /L applies only to the expression on which it appears.         There are yet more modifiers for controlling the way pcretest operates.
154    
155  The /I modifier requests that pcretest output information about the compiled         The  /+ modifier requests that as well as outputting the substring that
156  expression (whether it is anchored, has a fixed first character, and so on). It         matched the entire pattern, pcretest  should  in  addition  output  the
157  does this by calling pcre_fullinfo() after compiling an expression, and         remainder  of  the  subject  string. This is useful for tests where the
158  outputting the information it gets back. If the pattern is studied, the results         subject contains multiple copies of the same substring.
159  of that are also output.  
160           The /L modifier must be followed directly by the name of a locale,  for
161  The /D modifier is a PCRE debugging feature, which also assumes /I. It causes         example,
162  the internal form of compiled regular expressions to be output after  
163  compilation.           /pattern/Lfr_FR
164    
165  The /S modifier causes pcre_study() to be called after the expression has been         For this reason, it must be the last modifier. The given locale is set,
166  compiled, and the results used when the expression is matched.         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  The /M modifier causes the size of memory block used to hold the compiled         regular expression. Without an /L  modifier,  NULL  is  passed  as  the
169  pattern to be output.         tables  pointer; that is, /L applies only to the expression on which it
170           appears.
171  The /P modifier causes pcretest to call PCRE via the POSIX wrapper API rather  
172  than its native API. When this is done, all other modifiers except /i, /m, and         The /I modifier requests that pcretest  output  information  about  the
173  /+ are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is set if /m         compiled  pattern (whether it is anchored, has a fixed first character,
174  is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always, and         and so on). It does this by calling pcre_fullinfo() after  compiling  a
175  PCRE_DOTALL unless REG_NEWLINE is set.         pattern.  If  the pattern is studied, the results of that are also out-
176           put.
177  The /8 modifier causes pcretest to call PCRE with the PCRE_UTF8 option set.  
178  This turns on the (currently incomplete) support for UTF-8 character handling         The /D modifier is a PCRE debugging feature, which also assumes /I.  It
179  in PCRE, provided that it was compiled with this support enabled. This modifier         causes  the  internal form of compiled regular expressions to be output
180  also causes any non-printing characters in output strings to be printed using         after compilation. If the pattern was studied, the information returned
181  the \x{hh...} notation if they are valid UTF-8 sequences.         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  DATA LINES
 ----------  
   
 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:  
215    
216    \a         alarm (= BEL)         Before  each  data  line is passed to pcre_exec(), leading and trailing
217    \b         backspace         whitespace is removed, and it is then scanned for \  escapes.  Some  of
218    \e         escape         these  are  pretty esoteric features, intended for checking out some of
219    \f         formfeed         the more complicated features of PCRE. If you are just  testing  "ordi-
220    \n         newline         nary"  regular  expressions,  you probably don't need any of these. The
221    \r         carriage return         following escapes are recognized:
222    \t         tab  
223    \v         vertical tab           \a         alarm (= BEL)
224    \nnn       octal character (up to 3 octal digits)           \b         backspace
225    \xhh       hexadecimal character (up to 2 hex digits)           \e         escape
226    \x{hh...}  hexadecimal UTF-8 character           \f         formfeed
227             \n         newline
228    \A         pass the PCRE_ANCHORED option to pcre_exec()           \r         carriage return
229    \B         pass the PCRE_NOTBOL option to pcre_exec()           \t         tab
230    \Cdd       call pcre_copy_substring() for substring dd after a successful           \v         vertical tab
231                 match (any decimal number less than 32)           \nnn       octal character (up to 3 octal digits)
232    \Gdd       call pcre_get_substring() for substring dd after a successful           \xhh       hexadecimal character (up to 2 hex digits)
233                 match (any decimal number less than 32)           \x{hh...}  hexadecimal character, any number of digits
234    \L         call pcre_get_substringlist() after a successful match                        in UTF-8 mode
235    \N         pass the PCRE_NOTEMPTY option to pcre_exec()           \A         pass the PCRE_ANCHORED option to pcre_exec()
236    \Odd       set the size of the output vector passed to pcre_exec() to dd           \B         pass the PCRE_NOTBOL option to pcre_exec()
237                 (any number of decimal digits)           \Cdd       call pcre_copy_substring() for substring dd
238    \Z         pass the PCRE_NOTEOL option to pcre_exec()                        after a successful match (number less than 32)
239             \Cname     call pcre_copy_named_substring() for substring
240  A backslash followed by anything else just escapes the anything else. If the                        "name" after a successful match (name termin-
241  very last character is a backslash, it is ignored. This gives a way of passing                        ated by next non alphanumeric character)
242  an empty line as data, since a real empty line terminates the data input.           \C+        show the current captured substrings at callout
243                          time
244  If /P was present on the regex, causing the POSIX wrapper API to be used, only           \C-        do not supply a callout function
245  \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to           \C!n       return 1 instead of 0 when callout number n is
246  regexec() respectively.                        reached
247             \C!n!m     return 1 instead of 0 when callout number n is
248  The use of \x{hh...} to represent UTF-8 characters is not dependent on the use                        reached for the nth time
249  of the /8 modifier on the pattern. It is recognized always. There may be any           \C*n       pass the number n (may be negative) as callout
250  number of hexadecimal digits inside the braces. The result is from one to six                        data; this is used as the callout return value
251  bytes, encoded according to the UTF-8 rules.           \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  OUTPUT FROM PCRETEST                        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  When a match succeeds, pcretest outputs the list of captured substrings that                        ated by next non-alphanumeric character)
258  pcre_exec() returns, starting with number 0 for the string that matched the           \L         call pcre_get_substringlist() after a
259  whole pattern. Here is an example of an interactive pcretest run.                        successful match
260             \M         discover the minimum MATCH_LIMIT setting
261    $ pcretest           \N         pass the PCRE_NOTEMPTY option to pcre_exec()
262    PCRE version 2.06 08-Jun-1999           \Odd       set the size of the output vector passed to
263                          pcre_exec() to dd (any number of digits)
264      re> /^abc(\d+)/           \P         pass the PCRE_PARTIAL option to pcre_exec()
265    data> abc123                        or pcre_dfa_exec()
266     0: abc123           \R         pass the PCRE_DFA_RESTART option to pcre_dfa_exec()
267     1: 123           \S         output details of memory get/free calls during matching
268    data> xyz           \Z         pass the PCRE_NOTEOL option to pcre_exec()
269    No match           \?         pass the PCRE_NO_UTF8_CHECK option to
270                          pcre_exec()
271  If the strings contain any non-printing characters, they are output as \0x           \>dd       start the match at offset dd (any number of digits);
272  escapes, or as \x{...} escapes if the /8 modifier was present on the pattern.                        this sets the startoffset argument for pcre_exec()
273  If the pattern has the /+ modifier, then the output for substring 0 is followed  
274  by the the rest of the subject string, identified by "0+" like this:         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      re> /cat/+         way of passing an empty line as data, since a real  empty  line  termi-
277    data> cataract         nates the data input.
278     0: cat  
279     0+ aract         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  If the pattern has the /g or /G modifier, the results of successive matching         ture,  until it finds the minimum number that is needed for pcre_exec()
282  attempts are output in sequence, like this:         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      re> /\Bi(\w\w)/g         For most simple matches, the number is quite small,  but  for  patterns
285    data> Mississippi         with  very large numbers of matching possibilities, it can become large
286     0: iss         very quickly with increasing length of subject string.
287     1: ss  
288     0: iss         When \O is used, the value specified may be higher or  lower  than  the
289     1: ss         size set by the -O command line option (or defaulted to 45); \O applies
290     0: ipp         only to the call of pcre_exec() for the line in which it appears.
291     1: pp  
292           If the /P modifier was present on the pattern, causing the POSIX  wrap-
293  "No match" is output only if the first match attempt fails.         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  If any of \C, \G, or \L are present in a data line that is successfully  
296  matched, the substrings extracted by the convenience functions are output with         The use of \x{hh...} to represent UTF-8 characters is not dependent  on
297  C, G, or L after the string number instead of a colon. This is in addition to         the  use  of  the  /8 modifier on the pattern. It is recognized always.
298  the normal full list. The string length (that is, the return from the         There may be any number of hexadecimal digits inside  the  braces.  The
299  extraction function) is given in parentheses after each string for \C and \G.         result  is from one to six bytes, encoded according to the UTF-8 rules.
300    
301  Note that while patterns can be continued over several lines (a plain ">"  
302  prompt is used for continuations), data lines may not. However newlines can be  THE ALTERNATIVE MATCHING FUNCTION
303  included in data by means of the \n escape.  
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  COMMAND LINE OPTIONS         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  If the -p option is given to pcretest, it is equivalent to adding /P to each  
310  regular expression: the POSIX wrapper API is used to call PCRE. None of the         If a data line contains the \D escape sequence, or if the command  line
311  following flags has any effect in this case.         contains  the -dfa option, the alternative matching function is called.
312           This function finds all possible matches at a given point. If, however,
313  If the option -d is given to pcretest, it is equivalent to adding /D to each         the  \F escape sequence is present in the data line, it stops after the
314  regular expression: the internal form is output after compilation.         first match is found. This is always the shortest possible match.
315    
316  If the option -i is given to pcretest, it is equivalent to adding /I to each  
317  regular expression: information about the compiled pattern is given after  DEFAULT OUTPUT FROM PCRETEST
318  compilation.  
319           This section describes the output when the  normal  matching  function,
320  If the option -m is given to pcretest, it outputs the size of each compiled         pcre_exec(), is being used.
321  pattern after it has been compiled. It is equivalent to adding /M to each  
322  regular expression. For compatibility with earlier versions of pcretest, -s is         When a match succeeds, pcretest outputs the list of captured substrings
323  a synonym for -m.         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  If the -t option is given, each compile, study, and match is run 20000 times         match" when pcre_exec() returns PCRE_ERROR_NOMATCH  or  PCRE_ERROR_PAR-
326  while being timed, and the resulting time per compile or match is output in         TIAL,  respectively, and otherwise the PCRE negative error number. Here
327  milliseconds. Do not set -t with -m, because you will then get the size output         is an example of an interactive pcretest run.
328  20000 times and the timing will be distorted. If you want to change the number  
329  of repetitions used for timing, edit the definition of LOOPREPEAT at the top of           $ pcretest
330  pcretest.c           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  Philip Hazel <ph10@cam.ac.uk>  Last updated: 28 February 2005
529  August 2000  Copyright (c) 1997-2005 University of Cambridge.

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