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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             /<JS>           PCRE_JAVASCRIPT_COMPAT
164             /<cr>           PCRE_NEWLINE_CR
165             /<lf>           PCRE_NEWLINE_LF
166             /<crlf>         PCRE_NEWLINE_CRLF
167             /<anycrlf>      PCRE_NEWLINE_ANYCRLF
168             /<any>          PCRE_NEWLINE_ANY
169             /<bsr_anycrlf>  PCRE_BSR_ANYCRLF
170             /<bsr_unicode>  PCRE_BSR_UNICODE
171    
172           Those  specifying  line  ending sequences are literal strings as shown,
173           but the letters can be in either  case.  This  example  sets  multiline
174           matching with CRLF as the line ending sequence:
175    
176             /^abc/m<crlf>
177    
178           Details  of the meanings of these PCRE options are given in the pcreapi
179           documentation.
180    
181       Finding all matches in a string
182    
183           Searching for all possible matches within each subject  string  can  be
184           requested  by  the  /g  or  /G modifier. After finding a match, PCRE is
185           called again to search the remainder of the subject string. The differ-
186           ence between /g and /G is that the former uses the startoffset argument
187           to pcre_exec() to start searching at a  new  point  within  the  entire
188           string  (which  is in effect what Perl does), whereas the latter passes
189           over a shortened substring. This makes a  difference  to  the  matching
190           process if the pattern begins with a lookbehind assertion (including \b
191           or \B).
192    
193           If any call to pcre_exec() in a /g or  /G  sequence  matches  an  empty
194           string,  the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
195           flags set in order to search for another, non-empty, match at the  same
196           point.   If  this  second  match fails, the start offset is advanced by
197           one, and the normal match is retried. This imitates the way  Perl  han-
198           dles such cases when using the /g modifier or the split() function.
199    
200       Other modifiers
201    
202           There are yet more modifiers for controlling the way pcretest operates.
203    
204           The /+ modifier requests that as well as outputting the substring  that
205           matched  the  entire  pattern,  pcretest  should in addition output the
206           remainder of the subject string. This is useful  for  tests  where  the
207           subject contains multiple copies of the same substring.
208    
209           The  /B modifier is a debugging feature. It requests that pcretest out-
210           put a representation of the compiled byte code after compilation.  Nor-
211           mally  this  information contains length and offset values; however, if
212           /Z is also present, this data is replaced by spaces. This is a  special
213           feature for use in the automatic test scripts; it ensures that the same
214           output is generated for different internal link sizes.
215    
216           The /L modifier must be followed directly by the name of a locale,  for
217           example,
218    
219             /pattern/Lfr_FR
220    
221           For this reason, it must be the last modifier. The given locale is set,
222           pcre_maketables() is called to build a set of character tables for  the
223           locale,  and  this  is then passed to pcre_compile() when compiling the
224           regular expression. Without an /L  modifier,  NULL  is  passed  as  the
225           tables  pointer; that is, /L applies only to the expression on which it
226           appears.
227    
228           The /I modifier requests that pcretest  output  information  about  the
229           compiled  pattern (whether it is anchored, has a fixed first character,
230           and so on). It does this by calling pcre_fullinfo() after  compiling  a
231           pattern.  If  the pattern is studied, the results of that are also out-
232           put.
233    
234           The /D modifier is a PCRE debugging feature, and is equivalent to  /BI,
235           that is, both the /B and the /I modifiers.
236    
237           The /F modifier causes pcretest to flip the byte order of the fields in
238           the compiled pattern that  contain  2-byte  and  4-byte  numbers.  This
239           facility  is  for testing the feature in PCRE that allows it to execute
240           patterns that were compiled on a host with a different endianness. This
241           feature  is  not  available  when  the POSIX interface to PCRE is being
242           used, that is, when the /P pattern modifier is specified. See also  the
243           section about saving and reloading compiled patterns below.
244    
245           The  /S  modifier causes pcre_study() to be called after the expression
246           has been compiled, and the results used when the expression is matched.
247    
248           The  /M  modifier causes the size of memory block used to hold the com-
249           piled pattern to be output.
250    
251           The /P modifier causes pcretest to call PCRE via the POSIX wrapper  API
252           rather  than  its  native  API.  When this is done, all other modifiers
253           except /i, /m, and /+ are ignored. REG_ICASE is set if /i  is  present,
254           and  REG_NEWLINE  is  set if /m is present. The wrapper functions force
255           PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is  set.
256    
257           The  /8 modifier causes pcretest to call PCRE with the PCRE_UTF8 option
258           set. This turns on support for UTF-8 character handling in  PCRE,  pro-
259           vided  that  it  was  compiled with this support enabled. This modifier
260           also causes any non-printing characters in output strings to be printed
261           using the \x{hh...} notation if they are valid UTF-8 sequences.
262    
263           If  the  /?  modifier  is  used  with  /8,  it  causes pcretest to call
264           pcre_compile() with the  PCRE_NO_UTF8_CHECK  option,  to  suppress  the
265           checking of the string for UTF-8 validity.
266    
267    
268    DATA LINES
269    
270           Before  each  data  line is passed to pcre_exec(), leading and trailing
271           whitespace is removed, and it is then scanned for \  escapes.  Some  of
272           these  are  pretty esoteric features, intended for checking out some of
273           the more complicated features of PCRE. If you are just  testing  "ordi-
274           nary"  regular  expressions,  you probably don't need any of these. The
275           following escapes are recognized:
276    
277             \a         alarm (BEL, \x07)
278             \b         backspace (\x08)
279             \e         escape (\x27)
280             \f         formfeed (\x0c)
281             \n         newline (\x0a)
282             \qdd       set the PCRE_MATCH_LIMIT limit to dd
283                          (any number of digits)
284             \r         carriage return (\x0d)
285             \t         tab (\x09)
286             \v         vertical tab (\x0b)
287             \nnn       octal character (up to 3 octal digits)
288             \xhh       hexadecimal character (up to 2 hex digits)
289             \x{hh...}  hexadecimal character, any number of digits
290                          in UTF-8 mode
291             \A         pass the PCRE_ANCHORED option to pcre_exec()
292                          or pcre_dfa_exec()
293             \B         pass the PCRE_NOTBOL option to pcre_exec()
294                          or pcre_dfa_exec()
295             \Cdd       call pcre_copy_substring() for substring dd
296                          after a successful match (number less than 32)
297             \Cname     call pcre_copy_named_substring() for substring
298                          "name" after a successful match (name termin-
299                          ated by next non alphanumeric character)
300             \C+        show the current captured substrings at callout
301                          time
302             \C-        do not supply a callout function
303             \C!n       return 1 instead of 0 when callout number n is
304                          reached
305             \C!n!m     return 1 instead of 0 when callout number n is
306                          reached for the nth time
307             \C*n       pass the number n (may be negative) as callout
308                          data; this is used as the callout return value
309             \D         use the pcre_dfa_exec() match function
310             \F         only shortest match for pcre_dfa_exec()
311             \Gdd       call pcre_get_substring() for substring dd
312                          after a successful match (number less than 32)
313             \Gname     call pcre_get_named_substring() for substring
314                          "name" after a successful match (name termin-
315                          ated by next non-alphanumeric character)
316             \L         call pcre_get_substringlist() after a
317                          successful match
318             \M         discover the minimum MATCH_LIMIT and
319                          MATCH_LIMIT_RECURSION settings
320             \N         pass the PCRE_NOTEMPTY option to pcre_exec()
321                          or pcre_dfa_exec()
322             \Odd       set the size of the output vector passed to
323                          pcre_exec() to dd (any number of digits)
324             \P         pass the PCRE_PARTIAL option to pcre_exec()
325                          or pcre_dfa_exec()
326             \Qdd       set the PCRE_MATCH_LIMIT_RECURSION limit to dd
327                          (any number of digits)
328             \R         pass the PCRE_DFA_RESTART option to pcre_dfa_exec()
329             \S         output details of memory get/free calls during matching
330             \Z         pass the PCRE_NOTEOL option to pcre_exec()
331                          or pcre_dfa_exec()
332             \?         pass the PCRE_NO_UTF8_CHECK option to
333                          pcre_exec() or pcre_dfa_exec()
334             \>dd       start the match at offset dd (any number of digits);
335                          this sets the startoffset argument for pcre_exec()
336                          or pcre_dfa_exec()
337             \<cr>      pass the PCRE_NEWLINE_CR option to pcre_exec()
338                          or pcre_dfa_exec()
339             \<lf>      pass the PCRE_NEWLINE_LF option to pcre_exec()
340                          or pcre_dfa_exec()
341             \<crlf>    pass the PCRE_NEWLINE_CRLF option to pcre_exec()
342                          or pcre_dfa_exec()
343             \<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to pcre_exec()
344                          or pcre_dfa_exec()
345             \<any>     pass the PCRE_NEWLINE_ANY option to pcre_exec()
346                          or pcre_dfa_exec()
347    
348           The escapes that specify line ending  sequences  are  literal  strings,
349           exactly as shown. No more than one newline setting should be present in
350           any data line.
351    
352           A backslash followed by anything else just escapes the  anything  else.
353           If  the very last character is a backslash, it is ignored. This gives a
354           way of passing an empty line as data, since a real  empty  line  termi-
355           nates the data input.
356    
357           If  \M  is present, pcretest calls pcre_exec() several times, with dif-
358           ferent values in the match_limit and  match_limit_recursion  fields  of
359           the  pcre_extra  data structure, until it finds the minimum numbers for
360           each parameter that allow pcre_exec() to complete. The match_limit num-
361           ber  is  a  measure of the amount of backtracking that takes place, and
362           checking it out can be instructive. For most simple matches, the number
363           is  quite  small,  but for patterns with very large numbers of matching
364           possibilities, it can become large very quickly with increasing  length
365           of subject string. The match_limit_recursion number is a measure of how
366           much stack (or, if PCRE is compiled with  NO_RECURSE,  how  much  heap)
367           memory is needed to complete the match attempt.
368    
369           When  \O  is  used, the value specified may be higher or lower than the
370           size set by the -O command line option (or defaulted to 45); \O applies
371           only to the call of pcre_exec() for the line in which it appears.
372    
373           If  the /P modifier was present on the pattern, causing the POSIX wrap-
374           per API to be used, the only option-setting  sequences  that  have  any
375           effect  are \B and \Z, causing REG_NOTBOL and REG_NOTEOL, respectively,
376           to be passed to regexec().
377    
378           The use of \x{hh...} to represent UTF-8 characters is not dependent  on
379           the  use  of  the  /8 modifier on the pattern. It is recognized always.
380           There may be any number of hexadecimal digits inside  the  braces.  The
381           result  is  from  one  to  six bytes, encoded according to the original
382           UTF-8 rules of RFC 2279. This allows for  values  in  the  range  0  to
383           0x7FFFFFFF.  Note  that not all of those are valid Unicode code points,
384           or indeed valid UTF-8 characters according to the later  rules  in  RFC
385           3629.
386    
387    
388    THE ALTERNATIVE MATCHING FUNCTION
389    
390           By   default,  pcretest  uses  the  standard  PCRE  matching  function,
391           pcre_exec() to match each data line. From release 6.0, PCRE supports an
392           alternative  matching  function,  pcre_dfa_test(),  which operates in a
393           different way, and has some restrictions. The differences  between  the
394           two functions are described in the pcrematching documentation.
395    
396           If  a data line contains the \D escape sequence, or if the command line
397           contains the -dfa option, the alternative matching function is  called.
398           This function finds all possible matches at a given point. If, however,
399           the \F escape sequence is present in the data line, it stops after  the
400           first match is found. This is always the shortest possible match.
401    
402    
403    DEFAULT OUTPUT FROM PCRETEST
404    
405           This  section  describes  the output when the normal matching function,
406           pcre_exec(), is being used.
407    
408           When a match succeeds, pcretest outputs the list of captured substrings
409           that  pcre_exec()  returns,  starting with number 0 for the string that
410           matched the whole pattern. Otherwise, it outputs "No match" or "Partial
411           match"  when  pcre_exec() returns PCRE_ERROR_NOMATCH or PCRE_ERROR_PAR-
412           TIAL, respectively, and otherwise the PCRE negative error number.  Here
413           is an example of an interactive pcretest run.
414    
415             $ pcretest
416             PCRE version 7.0 30-Nov-2006
417    
418               re> /^abc(\d+)/
419             data> abc123
420              0: abc123
421              1: 123
422             data> xyz
423             No match
424    
425           Note  that unset capturing substrings that are not followed by one that
426           is set are not returned by pcre_exec(), and are not shown by  pcretest.
427           In  the following example, there are two capturing substrings, but when
428           the first data line is matched, the  second,  unset  substring  is  not
429           shown.  An "internal" unset substring is shown as "<unset>", as for the
430           second data line.
431    
432               re> /(a)|(b)/
433             data> a
434              0: a
435              1: a
436             data> b
437              0: b
438              1: <unset>
439              2: b
440    
441           If the strings contain any non-printing characters, they are output  as
442           \0x  escapes,  or  as \x{...} escapes if the /8 modifier was present on
443           the pattern. See below for the definition of  non-printing  characters.
444           If  the pattern has the /+ modifier, the output for substring 0 is fol-
445           lowed by the the rest of the subject string, identified  by  "0+"  like
446           this:
447    
448               re> /cat/+
449             data> cataract
450              0: cat
451              0+ aract
452    
453           If  the  pattern  has  the /g or /G modifier, the results of successive
454           matching attempts are output in sequence, like this:
455    
456               re> /\Bi(\w\w)/g
457             data> Mississippi
458              0: iss
459              1: ss
460              0: iss
461              1: ss
462              0: ipp
463              1: pp
464    
465           "No match" is output only if the first match attempt fails.
466    
467           If any of the sequences \C, \G, or \L are present in a data  line  that
468           is  successfully  matched,  the substrings extracted by the convenience
469           functions are output with C, G, or L after the string number instead of
470           a colon. This is in addition to the normal full list. The string length
471           (that is, the return from the extraction function) is given  in  paren-
472           theses after each string for \C and \G.
473    
474           Note that whereas patterns can be continued over several lines (a plain
475           ">" prompt is used for continuations), data lines may not. However new-
476           lines  can  be included in data by means of the \n escape (or \r, \r\n,
477           etc., depending on the newline sequence setting).
478    
479    
480    OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION
481    
482           When the alternative matching function, pcre_dfa_exec(),  is  used  (by
483           means  of  the \D escape sequence or the -dfa command line option), the
484           output consists of a list of all the matches that start  at  the  first
485           point in the subject where there is at least one match. For example:
486    
487               re> /(tang|tangerine|tan)/
488             data> yellow tangerine\D
489              0: tangerine
490              1: tang
491              2: tan
492    
493           (Using  the  normal  matching function on this data finds only "tang".)
494           The longest matching string is always given first (and numbered  zero).
495    
496           If /g is present on the pattern, the search for further matches resumes
497           at the end of the longest match. For example:
498    
499               re> /(tang|tangerine|tan)/g
500             data> yellow tangerine and tangy sultana\D
501              0: tangerine
502              1: tang
503              2: tan
504              0: tang
505              1: tan
506              0: tan
507    
508           Since the matching function does not  support  substring  capture,  the
509           escape  sequences  that  are concerned with captured substrings are not
510           relevant.
511    
512    
513    RESTARTING AFTER A PARTIAL MATCH
514    
515           When the alternative matching function has given the PCRE_ERROR_PARTIAL
516           return,  indicating that the subject partially matched the pattern, you
517           can restart the match with additional subject data by means of  the  \R
518           escape sequence. For example:
519    
520               re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/
521             data> 23ja\P\D
522             Partial match: 23ja
523             data> n05\R\D
524              0: n05
525    
526           For  further  information  about  partial matching, see the pcrepartial
527           documentation.
528    
529    
530    CALLOUTS
531    
532           If the pattern contains any callout requests, pcretest's callout  func-
533           tion  is  called  during  matching. This works with both matching func-
534           tions. By default, the called function displays the callout number, the
535           start  and  current  positions in the text at the callout time, and the
536           next pattern item to be tested. For example, the output
537    
538             --->pqrabcdef
539               0    ^  ^     \d
540    
541           indicates that callout number 0 occurred for a match  attempt  starting
542           at  the fourth character of the subject string, when the pointer was at
543           the seventh character of the data, and when the next pattern  item  was
544           \d.  Just  one  circumflex is output if the start and current positions
545           are the same.
546    
547           Callouts numbered 255 are assumed to be automatic callouts, inserted as
548           a  result  of the /C pattern modifier. In this case, instead of showing
549           the callout number, the offset in the pattern, preceded by a  plus,  is
550           output. For example:
551    
552               re> /\d?[A-E]\*/C
553             data> E*
554             --->E*
555              +0 ^      \d?
556              +3 ^      [A-E]
557              +8 ^^     \*
558             +10 ^ ^
559              0: E*
560    
561           The  callout  function  in pcretest returns zero (carry on matching) by
562           default, but you can use a \C item in a data line (as described  above)
563           to change this.
564    
565           Inserting  callouts can be helpful when using pcretest to check compli-
566           cated regular expressions. For further information about callouts,  see
567           the pcrecallout documentation.
568    
569    
570    NON-PRINTING CHARACTERS
571    
572           When  pcretest is outputting text in the compiled version of a pattern,
573           bytes other than 32-126 are always treated as  non-printing  characters
574           are are therefore shown as hex escapes.
575    
576           When  pcretest  is  outputting text that is a matched part of a subject
577           string, it behaves in the same way, unless a different locale has  been
578           set  for  the  pattern  (using  the  /L  modifier).  In  this case, the
579           isprint() function to distinguish printing and non-printing characters.
580    
581    
582    SAVING AND RELOADING COMPILED PATTERNS
583    
584           The  facilities  described  in  this section are not available when the
585           POSIX inteface to PCRE is being used, that is, when the /P pattern mod-
586           ifier is specified.
587    
588           When the POSIX interface is not in use, you can cause pcretest to write
589           a compiled pattern to a file, by following the modifiers with >  and  a
590           file name.  For example:
591    
592             /pattern/im >/some/file
593    
594           See  the pcreprecompile documentation for a discussion about saving and
595           re-using compiled patterns.
596    
597           The data that is written is binary.  The  first  eight  bytes  are  the
598           length  of  the  compiled  pattern  data  followed by the length of the
599           optional study data, each written as four  bytes  in  big-endian  order
600           (most  significant  byte  first). If there is no study data (either the
601           pattern was not studied, or studying did not return any data), the sec-
602           ond  length  is  zero. The lengths are followed by an exact copy of the
603           compiled pattern. If there is additional study data, this follows imme-
604           diately  after  the  compiled pattern. After writing the file, pcretest
605           expects to read a new pattern.
606    
607           A saved pattern can be reloaded into pcretest by specifing < and a file
608           name  instead  of  a pattern. The name of the file must not contain a <
609           character, as otherwise pcretest will interpret the line as  a  pattern
610           delimited by < characters.  For example:
611    
612              re> </some/file
613             Compiled regex loaded from /some/file
614             No study data
615    
616           When  the pattern has been loaded, pcretest proceeds to read data lines
617           in the usual way.
618    
619           You can copy a file written by pcretest to a different host and  reload
620           it  there,  even  if the new host has opposite endianness to the one on
621           which the pattern was compiled. For example, you can compile on an  i86
622           machine and run on a SPARC machine.
623    
624           File  names  for  saving and reloading can be absolute or relative, but
625           note that the shell facility of expanding a file name that starts  with
626           a tilde (~) is not available.
627    
628           The  ability to save and reload files in pcretest is intended for test-
629           ing and experimentation. It is not intended for production use  because
630           only  a  single pattern can be written to a file. Furthermore, there is
631           no facility for supplying  custom  character  tables  for  use  with  a
632           reloaded  pattern.  If  the  original  pattern was compiled with custom
633           tables, an attempt to match a subject string using a  reloaded  pattern
634           is  likely to cause pcretest to crash.  Finally, if you attempt to load
635           a file that is not in the correct format, the result is undefined.
636    
637    
638    SEE ALSO
639    
640           pcre(3), pcreapi(3), pcrecallout(3),  pcrematching(3),  pcrepartial(d),
641           pcrepattern(3), pcreprecompile(3).
642    
643    
644    AUTHOR
645    
646           Philip Hazel
647           University Computing Service
648           Cambridge CB2 3QH, England.
649    
650    
651    REVISION
652    
653           Last updated: 12 April 2008
654           Copyright (c) 1997-2008 University of Cambridge.

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