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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    
4  If it is given two filename arguments, it reads from the first and writes to  NAME
5  the second. If it is given only one filename argument, it reads from that file         pcretest - a program for testing Perl-compatible regular expressions.
 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 and PCRE_ANCHORED flags set in order  
 to search for another, non-empty, match at the same point. If this second match  
 fails, the start offset is advanced by one, and the normal 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  
6    
7  Philip Hazel <ph10@cam.ac.uk>  
8  January 2000  SYNOPSIS
9    
10           pcretest [options] [source] [destination]
11    
12           pcretest  was written as a test program for the PCRE regular expression
13           library itself, but it can also be used for experimenting with  regular
14           expressions.  This document describes the features of the test program;
15           for details of the regular expressions themselves, see the  pcrepattern
16           documentation. For details of the PCRE library function calls and their
17           options, see the pcreapi documentation.
18    
19    
20    OPTIONS
21    
22           -b        Behave as if each regex has the /B (show bytecode)  modifier;
23                     the internal form is output after compilation.
24    
25           -C        Output the version number of the PCRE library, and all avail-
26                     able  information  about  the  optional  features  that   are
27                     included, and then exit.
28    
29           -d        Behave  as  if  each  regex  has the /D (debug) modifier; the
30                     internal form and information about the compiled  pattern  is
31                     output after compilation; -d is equivalent to -b -i.
32    
33           -dfa      Behave  as if each data line contains the \D escape sequence;
34                     this    causes    the    alternative    matching    function,
35                     pcre_dfa_exec(),   to   be   used  instead  of  the  standard
36                     pcre_exec() function (more detail is given below).
37    
38           -help     Output a brief summary these options and then exit.
39    
40           -i        Behave as if each regex  has  the  /I  modifier;  information
41                     about the compiled pattern is given after compilation.
42    
43           -m        Output  the  size  of each compiled pattern after it has been
44                     compiled. This is equivalent to adding  /M  to  each  regular
45                     expression.   For  compatibility  with  earlier  versions  of
46                     pcretest, -s is a synonym for -m.
47    
48           -o osize  Set the number of elements in the output vector that is  used
49                     when  calling pcre_exec() or pcre_dfa_exec() to be osize. The
50                     default value is 45, which is enough for 14 capturing  subex-
51                     pressions   for  pcre_exec()  or  22  different  matches  for
52                     pcre_dfa_exec(). The vector size can be changed for  individ-
53                     ual  matching  calls  by  including  \O in the data line (see
54                     below).
55    
56           -p        Behave as if each regex has the /P modifier; the POSIX  wrap-
57                     per  API  is used to call PCRE. None of the other options has
58                     any effect when -p is set.
59    
60           -q        Do not output the version number of pcretest at the start  of
61                     execution.
62    
63           -S size   On  Unix-like  systems,  set the size of the runtime stack to
64                     size megabytes.
65    
66           -t        Run each compile, study, and match many times with  a  timer,
67                     and  output resulting time per compile or match (in millisec-
68                     onds). Do not set -m with -t, because you will then  get  the
69                     size  output  a  zillion  times,  and the timing will be dis-
70                     torted. You can control the number  of  iterations  that  are
71                     used  for timing by following -t with a number (as a separate
72                     item on the command line). For example, "-t 1000" would iter-
73                     ate 1000 times. The default is to iterate 500000 times.
74    
75           -tm       This is like -t except that it times only the matching phase,
76                     not the compile or study phases.
77    
78    
79    DESCRIPTION
80    
81           If pcretest is given two filename arguments, it reads  from  the  first
82           and writes to the second. If it is given only one filename argument, it
83           reads from that file and writes to stdout.  Otherwise,  it  reads  from
84           stdin  and  writes to stdout, and prompts for each line of input, using
85           "re>" to prompt for regular expressions, and "data>" to prompt for data
86           lines.
87    
88           When  pcretest  is  built,  a  configuration option can specify that it
89           should be linked with the libreadline library. When this  is  done,  if
90           the input is from a terminal, it is read using the readline() function.
91           This provides line-editing and history facilities. The output from  the
92           -help option states whether or not readline() will be used.
93    
94           The program handles any number of sets of input on a single input file.
95           Each set starts with a regular expression, and continues with any  num-
96           ber of data lines to be matched against the pattern.
97    
98           Each  data line is matched separately and independently. If you want to
99           do multi-line matches, you have to use the \n escape sequence (or \r or
100           \r\n, etc., depending on the newline setting) in a single line of input
101           to encode the newline sequences. There is no limit  on  the  length  of
102           data  lines;  the  input  buffer is automatically extended if it is too
103           small.
104    
105           An empty line signals the end of the data lines, at which point  a  new
106           regular  expression is read. The regular expressions are given enclosed
107           in any non-alphanumeric delimiters other than backslash, for example:
108    
109             /(a|bc)x+yz/
110    
111           White space before the initial delimiter is ignored. A regular  expres-
112           sion  may be continued over several input lines, in which case the new-
113           line characters are included within it. It is possible to  include  the
114           delimiter within the pattern by escaping it, for example
115    
116             /abc\/def/
117    
118           If  you  do  so, the escape and the delimiter form part of the pattern,
119           but since delimiters are always non-alphanumeric, this does not  affect
120           its  interpretation.   If the terminating delimiter is immediately fol-
121           lowed by a backslash, for example,
122    
123             /abc/\
124    
125           then a backslash is added to the end of the pattern. This  is  done  to
126           provide  a  way of testing the error condition that arises if a pattern
127           finishes with a backslash, because
128    
129             /abc\/
130    
131           is interpreted as the first line of a pattern that starts with  "abc/",
132           causing pcretest to read the next line as a continuation of the regular
133           expression.
134    
135    
136    PATTERN MODIFIERS
137    
138           A pattern may be followed by any number of modifiers, which are  mostly
139           single  characters.  Following  Perl usage, these are referred to below
140           as, for example, "the /i modifier", even though the  delimiter  of  the
141           pattern  need  not always be a slash, and no slash is used when writing
142           modifiers. Whitespace may appear between the  final  pattern  delimiter
143           and the first modifier, and between the modifiers themselves.
144    
145           The /i, /m, /s, and /x modifiers set the PCRE_CASELESS, PCRE_MULTILINE,
146           PCRE_DOTALL, or PCRE_EXTENDED  options,  respectively,  when  pcre_com-
147           pile()  is  called. These four modifier letters have the same effect as
148           they do in Perl. For example:
149    
150             /caseless/i
151    
152           The following table shows additional modifiers for setting PCRE options
153           that do not correspond to anything in Perl:
154    
155             /A              PCRE_ANCHORED
156             /C              PCRE_AUTO_CALLOUT
157             /E              PCRE_DOLLAR_ENDONLY
158             /f              PCRE_FIRSTLINE
159             /J              PCRE_DUPNAMES
160             /N              PCRE_NO_AUTO_CAPTURE
161             /U              PCRE_UNGREEDY
162             /X              PCRE_EXTRA
163             /<cr>           PCRE_NEWLINE_CR
164             /<lf>           PCRE_NEWLINE_LF
165             /<crlf>         PCRE_NEWLINE_CRLF
166             /<anycrlf>      PCRE_NEWLINE_ANYCRLF
167             /<any>          PCRE_NEWLINE_ANY
168             /<bsr_anycrlf>  PCRE_BSR_ANYCRLF
169             /<bsr_unicode>  PCRE_BSR_UNICODE
170    
171           Those  specifying  line  ending sequences are literal strings as shown,
172           but the letters can be in either  case.  This  example  sets  multiline
173           matching with CRLF as the line ending sequence:
174    
175             /^abc/m<crlf>
176    
177           Details  of the meanings of these PCRE options are given in the pcreapi
178           documentation.
179    
180       Finding all matches in a string
181    
182           Searching for all possible matches within each subject  string  can  be
183           requested  by  the  /g  or  /G modifier. After finding a match, PCRE is
184           called again to search the remainder of the subject string. The differ-
185           ence between /g and /G is that the former uses the startoffset argument
186           to pcre_exec() to start searching at a  new  point  within  the  entire
187           string  (which  is in effect what Perl does), whereas the latter passes
188           over a shortened substring. This makes a  difference  to  the  matching
189           process if the pattern begins with a lookbehind assertion (including \b
190           or \B).
191    
192           If any call to pcre_exec() in a /g or  /G  sequence  matches  an  empty
193           string,  the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
194           flags set in order to search for another, non-empty, match at the  same
195           point.   If  this  second  match fails, the start offset is advanced by
196           one, and the normal match is retried. This imitates the way  Perl  han-
197           dles such cases when using the /g modifier or the split() function.
198    
199       Other modifiers
200    
201           There are yet more modifiers for controlling the way pcretest operates.
202    
203           The /+ modifier requests that as well as outputting the substring  that
204           matched  the  entire  pattern,  pcretest  should in addition output the
205           remainder of the subject string. This is useful  for  tests  where  the
206           subject contains multiple copies of the same substring.
207    
208           The  /B modifier is a debugging feature. It requests that pcretest out-
209           put a representation of the compiled byte code after compilation.  Nor-
210           mally  this  information contains length and offset values; however, if
211           /Z is also present, this data is replaced by spaces. This is a  special
212           feature for use in the automatic test scripts; it ensures that the same
213           output is generated for different internal link sizes.
214    
215           The /L modifier must be followed directly by the name of a locale,  for
216           example,
217    
218             /pattern/Lfr_FR
219    
220           For this reason, it must be the last modifier. The given locale is set,
221           pcre_maketables() is called to build a set of character tables for  the
222           locale,  and  this  is then passed to pcre_compile() when compiling the
223           regular expression. Without an /L  modifier,  NULL  is  passed  as  the
224           tables  pointer; that is, /L applies only to the expression on which it
225           appears.
226    
227           The /I modifier requests that pcretest  output  information  about  the
228           compiled  pattern (whether it is anchored, has a fixed first character,
229           and so on). It does this by calling pcre_fullinfo() after  compiling  a
230           pattern.  If  the pattern is studied, the results of that are also out-
231           put.
232    
233           The /D modifier is a PCRE debugging feature, and is equivalent to  /BI,
234           that is, both the /B and the /I modifiers.
235    
236           The /F modifier causes pcretest to flip the byte order of the fields in
237           the compiled pattern that  contain  2-byte  and  4-byte  numbers.  This
238           facility  is  for testing the feature in PCRE that allows it to execute
239           patterns that were compiled on a host with a different endianness. This
240           feature  is  not  available  when  the POSIX interface to PCRE is being
241           used, that is, when the /P pattern modifier is specified. See also  the
242           section about saving and reloading compiled patterns below.
243    
244           The  /S  modifier causes pcre_study() to be called after the expression
245           has been compiled, and the results used when the expression is matched.
246    
247           The  /M  modifier causes the size of memory block used to hold the com-
248           piled pattern to be output.
249    
250           The /P modifier causes pcretest to call PCRE via the POSIX wrapper  API
251           rather  than  its  native  API.  When this is done, all other modifiers
252           except /i, /m, and /+ are ignored. REG_ICASE is set if /i  is  present,
253           and  REG_NEWLINE  is  set if /m is present. The wrapper functions force
254           PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is  set.
255    
256           The  /8 modifier causes pcretest to call PCRE with the PCRE_UTF8 option
257           set. This turns on support for UTF-8 character handling in  PCRE,  pro-
258           vided  that  it  was  compiled with this support enabled. This modifier
259           also causes any non-printing characters in output strings to be printed
260           using the \x{hh...} notation if they are valid UTF-8 sequences.
261    
262           If  the  /?  modifier  is  used  with  /8,  it  causes pcretest to call
263           pcre_compile() with the  PCRE_NO_UTF8_CHECK  option,  to  suppress  the
264           checking of the string for UTF-8 validity.
265    
266    
267    DATA LINES
268    
269           Before  each  data  line is passed to pcre_exec(), leading and trailing
270           whitespace is removed, and it is then scanned for \  escapes.  Some  of
271           these  are  pretty esoteric features, intended for checking out some of
272           the more complicated features of PCRE. If you are just  testing  "ordi-
273           nary"  regular  expressions,  you probably don't need any of these. The
274           following escapes are recognized:
275    
276             \a         alarm (BEL, \x07)
277             \b         backspace (\x08)
278             \e         escape (\x27)
279             \f         formfeed (\x0c)
280             \n         newline (\x0a)
281             \qdd       set the PCRE_MATCH_LIMIT limit to dd
282                          (any number of digits)
283             \r         carriage return (\x0d)
284             \t         tab (\x09)
285             \v         vertical tab (\x0b)
286             \nnn       octal character (up to 3 octal digits)
287             \xhh       hexadecimal character (up to 2 hex digits)
288             \x{hh...}  hexadecimal character, any number of digits
289                          in UTF-8 mode
290             \A         pass the PCRE_ANCHORED option to pcre_exec()
291                          or pcre_dfa_exec()
292             \B         pass the PCRE_NOTBOL option to pcre_exec()
293                          or pcre_dfa_exec()
294             \Cdd       call pcre_copy_substring() for substring dd
295                          after a successful match (number less than 32)
296             \Cname     call pcre_copy_named_substring() for substring
297                          "name" after a successful match (name termin-
298                          ated by next non alphanumeric character)
299             \C+        show the current captured substrings at callout
300                          time
301             \C-        do not supply a callout function
302             \C!n       return 1 instead of 0 when callout number n is
303                          reached
304             \C!n!m     return 1 instead of 0 when callout number n is
305                          reached for the nth time
306             \C*n       pass the number n (may be negative) as callout
307                          data; this is used as the callout return value
308             \D         use the pcre_dfa_exec() match function
309             \F         only shortest match for pcre_dfa_exec()
310             \Gdd       call pcre_get_substring() for substring dd
311                          after a successful match (number less than 32)
312             \Gname     call pcre_get_named_substring() for substring
313                          "name" after a successful match (name termin-
314                          ated by next non-alphanumeric character)
315             \L         call pcre_get_substringlist() after a
316                          successful match
317             \M         discover the minimum MATCH_LIMIT and
318                          MATCH_LIMIT_RECURSION settings
319             \N         pass the PCRE_NOTEMPTY option to pcre_exec()
320                          or pcre_dfa_exec()
321             \Odd       set the size of the output vector passed to
322                          pcre_exec() to dd (any number of digits)
323             \P         pass the PCRE_PARTIAL option to pcre_exec()
324                          or pcre_dfa_exec()
325             \Qdd       set the PCRE_MATCH_LIMIT_RECURSION limit to dd
326                          (any number of digits)
327             \R         pass the PCRE_DFA_RESTART option to pcre_dfa_exec()
328             \S         output details of memory get/free calls during matching
329             \Z         pass the PCRE_NOTEOL option to pcre_exec()
330                          or pcre_dfa_exec()
331             \?         pass the PCRE_NO_UTF8_CHECK option to
332                          pcre_exec() or pcre_dfa_exec()
333             \>dd       start the match at offset dd (any number of digits);
334                          this sets the startoffset argument for pcre_exec()
335                          or pcre_dfa_exec()
336             \<cr>      pass the PCRE_NEWLINE_CR option to pcre_exec()
337                          or pcre_dfa_exec()
338             \<lf>      pass the PCRE_NEWLINE_LF option to pcre_exec()
339                          or pcre_dfa_exec()
340             \<crlf>    pass the PCRE_NEWLINE_CRLF option to pcre_exec()
341                          or pcre_dfa_exec()
342             \<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to pcre_exec()
343                          or pcre_dfa_exec()
344             \<any>     pass the PCRE_NEWLINE_ANY option to pcre_exec()
345                          or pcre_dfa_exec()
346    
347           The escapes that specify line ending  sequences  are  literal  strings,
348           exactly as shown. No more than one newline setting should be present in
349           any data line.
350    
351           A backslash followed by anything else just escapes the  anything  else.
352           If  the very last character is a backslash, it is ignored. This gives a
353           way of passing an empty line as data, since a real  empty  line  termi-
354           nates the data input.
355    
356           If  \M  is present, pcretest calls pcre_exec() several times, with dif-
357           ferent values in the match_limit and  match_limit_recursion  fields  of
358           the  pcre_extra  data structure, until it finds the minimum numbers for
359           each parameter that allow pcre_exec() to complete. The match_limit num-
360           ber  is  a  measure of the amount of backtracking that takes place, and
361           checking it out can be instructive. For most simple matches, the number
362           is  quite  small,  but for patterns with very large numbers of matching
363           possibilities, it can become large very quickly with increasing  length
364           of subject string. The match_limit_recursion number is a measure of how
365           much stack (or, if PCRE is compiled with  NO_RECURSE,  how  much  heap)
366           memory is needed to complete the match attempt.
367    
368           When  \O  is  used, the value specified may be higher or lower than the
369           size set by the -O command line option (or defaulted to 45); \O applies
370           only to the call of pcre_exec() for the line in which it appears.
371    
372           If  the /P modifier was present on the pattern, causing the POSIX wrap-
373           per API to be used, the only option-setting  sequences  that  have  any
374           effect  are \B and \Z, causing REG_NOTBOL and REG_NOTEOL, respectively,
375           to be passed to regexec().
376    
377           The use of \x{hh...} to represent UTF-8 characters is not dependent  on
378           the  use  of  the  /8 modifier on the pattern. It is recognized always.
379           There may be any number of hexadecimal digits inside  the  braces.  The
380           result  is  from  one  to  six bytes, encoded according to the original
381           UTF-8 rules of RFC 2279. This allows for  values  in  the  range  0  to
382           0x7FFFFFFF.  Note  that not all of those are valid Unicode code points,
383           or indeed valid UTF-8 characters according to the later  rules  in  RFC
384           3629.
385    
386    
387    THE ALTERNATIVE MATCHING FUNCTION
388    
389           By   default,  pcretest  uses  the  standard  PCRE  matching  function,
390           pcre_exec() to match each data line. From release 6.0, PCRE supports an
391           alternative  matching  function,  pcre_dfa_test(),  which operates in a
392           different way, and has some restrictions. The differences  between  the
393           two functions are described in the pcrematching documentation.
394    
395           If  a data line contains the \D escape sequence, or if the command line
396           contains the -dfa option, the alternative matching function is  called.
397           This function finds all possible matches at a given point. If, however,
398           the \F escape sequence is present in the data line, it stops after  the
399           first match is found. This is always the shortest possible match.
400    
401    
402    DEFAULT OUTPUT FROM PCRETEST
403    
404           This  section  describes  the output when the normal matching function,
405           pcre_exec(), is being used.
406    
407           When a match succeeds, pcretest outputs the list of captured substrings
408           that  pcre_exec()  returns,  starting with number 0 for the string that
409           matched the whole pattern. Otherwise, it outputs "No match" or "Partial
410           match"  when  pcre_exec() returns PCRE_ERROR_NOMATCH or PCRE_ERROR_PAR-
411           TIAL, respectively, and otherwise the PCRE negative error number.  Here
412           is an example of an interactive pcretest run.
413    
414             $ pcretest
415             PCRE version 7.0 30-Nov-2006
416    
417               re> /^abc(\d+)/
418             data> abc123
419              0: abc123
420              1: 123
421             data> xyz
422             No match
423    
424           Note  that unset capturing substrings that are not followed by one that
425           is set are not returned by pcre_exec(), and are not shown by  pcretest.
426           In  the following example, there are two capturing substrings, but when
427           the first data line is matched, the  second,  unset  substring  is  not
428           shown.  An "internal" unset substring is shown as "<unset>", as for the
429           second data line.
430    
431               re> /(a)|(b)/
432             data> a
433              0: a
434              1: a
435             data> b
436              0: b
437              1: <unset>
438              2: b
439    
440           If the strings contain any non-printing characters, they are output  as
441           \0x  escapes,  or  as \x{...} escapes if the /8 modifier was present on
442           the pattern. See below for the definition of  non-printing  characters.
443           If  the pattern has the /+ modifier, the output for substring 0 is fol-
444           lowed by the the rest of the subject string, identified  by  "0+"  like
445           this:
446    
447               re> /cat/+
448             data> cataract
449              0: cat
450              0+ aract
451    
452           If  the  pattern  has  the /g or /G modifier, the results of successive
453           matching attempts are output in sequence, like this:
454    
455               re> /\Bi(\w\w)/g
456             data> Mississippi
457              0: iss
458              1: ss
459              0: iss
460              1: ss
461              0: ipp
462              1: pp
463    
464           "No match" is output only if the first match attempt fails.
465    
466           If any of the sequences \C, \G, or \L are present in a data  line  that
467           is  successfully  matched,  the substrings extracted by the convenience
468           functions are output with C, G, or L after the string number instead of
469           a colon. This is in addition to the normal full list. The string length
470           (that is, the return from the extraction function) is given  in  paren-
471           theses after each string for \C and \G.
472    
473           Note that whereas patterns can be continued over several lines (a plain
474           ">" prompt is used for continuations), data lines may not. However new-
475           lines  can  be included in data by means of the \n escape (or \r, \r\n,
476           etc., depending on the newline sequence setting).
477    
478    
479    OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION
480    
481           When the alternative matching function, pcre_dfa_exec(),  is  used  (by
482           means  of  the \D escape sequence or the -dfa command line option), the
483           output consists of a list of all the matches that start  at  the  first
484           point in the subject where there is at least one match. For example:
485    
486               re> /(tang|tangerine|tan)/
487             data> yellow tangerine\D
488              0: tangerine
489              1: tang
490              2: tan
491    
492           (Using  the  normal  matching function on this data finds only "tang".)
493           The longest matching string is always given first (and numbered  zero).
494    
495           If /g is present on the pattern, the search for further matches resumes
496           at the end of the longest match. For example:
497    
498               re> /(tang|tangerine|tan)/g
499             data> yellow tangerine and tangy sultana\D
500              0: tangerine
501              1: tang
502              2: tan
503              0: tang
504              1: tan
505              0: tan
506    
507           Since the matching function does not  support  substring  capture,  the
508           escape  sequences  that  are concerned with captured substrings are not
509           relevant.
510    
511    
512    RESTARTING AFTER A PARTIAL MATCH
513    
514           When the alternative matching function has given the PCRE_ERROR_PARTIAL
515           return,  indicating that the subject partially matched the pattern, you
516           can restart the match with additional subject data by means of  the  \R
517           escape sequence. For example:
518    
519               re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/
520             data> 23ja\P\D
521             Partial match: 23ja
522             data> n05\R\D
523              0: n05
524    
525           For  further  information  about  partial matching, see the pcrepartial
526           documentation.
527    
528    
529    CALLOUTS
530    
531           If the pattern contains any callout requests, pcretest's callout  func-
532           tion  is  called  during  matching. This works with both matching func-
533           tions. By default, the called function displays the callout number, the
534           start  and  current  positions in the text at the callout time, and the
535           next pattern item to be tested. For example, the output
536    
537             --->pqrabcdef
538               0    ^  ^     \d
539    
540           indicates that callout number 0 occurred for a match  attempt  starting
541           at  the fourth character of the subject string, when the pointer was at
542           the seventh character of the data, and when the next pattern  item  was
543           \d.  Just  one  circumflex is output if the start and current positions
544           are the same.
545    
546           Callouts numbered 255 are assumed to be automatic callouts, inserted as
547           a  result  of the /C pattern modifier. In this case, instead of showing
548           the callout number, the offset in the pattern, preceded by a  plus,  is
549           output. For example:
550    
551               re> /\d?[A-E]\*/C
552             data> E*
553             --->E*
554              +0 ^      \d?
555              +3 ^      [A-E]
556              +8 ^^     \*
557             +10 ^ ^
558              0: E*
559    
560           The  callout  function  in pcretest returns zero (carry on matching) by
561           default, but you can use a \C item in a data line (as described  above)
562           to change this.
563    
564           Inserting  callouts can be helpful when using pcretest to check compli-
565           cated regular expressions. For further information about callouts,  see
566           the pcrecallout documentation.
567    
568    
569    NON-PRINTING CHARACTERS
570    
571           When  pcretest is outputting text in the compiled version of a pattern,
572           bytes other than 32-126 are always treated as  non-printing  characters
573           are are therefore shown as hex escapes.
574    
575           When  pcretest  is  outputting text that is a matched part of a subject
576           string, it behaves in the same way, unless a different locale has  been
577           set  for  the  pattern  (using  the  /L  modifier).  In  this case, the
578           isprint() function to distinguish printing and non-printing characters.
579    
580    
581    SAVING AND RELOADING COMPILED PATTERNS
582    
583           The  facilities  described  in  this section are not available when the
584           POSIX inteface to PCRE is being used, that is, when the /P pattern mod-
585           ifier is specified.
586    
587           When the POSIX interface is not in use, you can cause pcretest to write
588           a compiled pattern to a file, by following the modifiers with >  and  a
589           file name.  For example:
590    
591             /pattern/im >/some/file
592    
593           See  the pcreprecompile documentation for a discussion about saving and
594           re-using compiled patterns.
595    
596           The data that is written is binary.  The  first  eight  bytes  are  the
597           length  of  the  compiled  pattern  data  followed by the length of the
598           optional study data, each written as four  bytes  in  big-endian  order
599           (most  significant  byte  first). If there is no study data (either the
600           pattern was not studied, or studying did not return any data), the sec-
601           ond  length  is  zero. The lengths are followed by an exact copy of the
602           compiled pattern. If there is additional study data, this follows imme-
603           diately  after  the  compiled pattern. After writing the file, pcretest
604           expects to read a new pattern.
605    
606           A saved pattern can be reloaded into pcretest by specifing < and a file
607           name  instead  of  a pattern. The name of the file must not contain a <
608           character, as otherwise pcretest will interpret the line as  a  pattern
609           delimited by < characters.  For example:
610    
611              re> </some/file
612             Compiled regex loaded from /some/file
613             No study data
614    
615           When  the pattern has been loaded, pcretest proceeds to read data lines
616           in the usual way.
617    
618           You can copy a file written by pcretest to a different host and  reload
619           it  there,  even  if the new host has opposite endianness to the one on
620           which the pattern was compiled. For example, you can compile on an  i86
621           machine and run on a SPARC machine.
622    
623           File  names  for  saving and reloading can be absolute or relative, but
624           note that the shell facility of expanding a file name that starts  with
625           a tilde (~) is not available.
626    
627           The  ability to save and reload files in pcretest is intended for test-
628           ing and experimentation. It is not intended for production use  because
629           only  a  single pattern can be written to a file. Furthermore, there is
630           no facility for supplying  custom  character  tables  for  use  with  a
631           reloaded  pattern.  If  the  original  pattern was compiled with custom
632           tables, an attempt to match a subject string using a  reloaded  pattern
633           is  likely to cause pcretest to crash.  Finally, if you attempt to load
634           a file that is not in the correct format, the result is undefined.
635    
636    
637    SEE ALSO
638    
639           pcre(3), pcreapi(3), pcrecallout(3),  pcrematching(3),  pcrepartial(d),
640           pcrepattern(3), pcreprecompile(3).
641    
642    
643    AUTHOR
644    
645           Philip Hazel
646           University Computing Service
647           Cambridge CB2 3QH, England.
648    
649    
650    REVISION
651    
652           Last updated: 18 December 2007
653           Copyright (c) 1997-2007 University of Cambridge.

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