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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        Behave  as if each data line contains the \M escape sequence;
44                     this causes PCRE to  discover  the  minimum  MATCH_LIMIT  and
45                     MATCH_LIMIT_RECURSION settings by calling pcre_exec() repeat-
46                     edly with different limits.
47    
48           -m        Output the size of each compiled pattern after  it  has  been
49                     compiled.  This  is  equivalent  to adding /M to each regular
50                     expression.  For  compatibility  with  earlier  versions   of
51                     pcretest, -s is a synonym for -m.
52    
53           -o osize  Set  the number of elements in the output vector that is used
54                     when calling pcre_exec() or pcre_dfa_exec() to be osize.  The
55                     default  value is 45, which is enough for 14 capturing subex-
56                     pressions  for  pcre_exec()  or  22  different  matches   for
57                     pcre_dfa_exec().  The vector size can be changed for individ-
58                     ual matching calls by including \O  in  the  data  line  (see
59                     below).
60    
61           -p        Behave  as if each regex has the /P modifier; the POSIX wrap-
62                     per API is used to call PCRE. None of the other  options  has
63                     any effect when -p is set.
64    
65           -q        Do  not output the version number of pcretest at the start of
66                     execution.
67    
68           -S size   On Unix-like systems, set the size of the  runtime  stack  to
69                     size megabytes.
70    
71           -t        Run  each  compile, study, and match many times with a timer,
72                     and output resulting time per compile or match (in  millisec-
73                     onds).  Do  not set -m with -t, because you will then get the
74                     size output a zillion times, and  the  timing  will  be  dis-
75                     torted.  You  can  control  the number of iterations that are
76                     used for timing by following -t with a number (as a  separate
77                     item on the command line). For example, "-t 1000" would iter-
78                     ate 1000 times. The default is to iterate 500000 times.
79    
80           -tm       This is like -t except that it times only the matching phase,
81                     not the compile or study phases.
82    
83    
84    DESCRIPTION
85    
86           If  pcretest  is  given two filename arguments, it reads from the first
87           and writes to the second. If it is given only one filename argument, it
88           reads  from  that  file  and writes to stdout. Otherwise, it reads from
89           stdin and writes to stdout, and prompts for each line of  input,  using
90           "re>" to prompt for regular expressions, and "data>" to prompt for data
91           lines.
92    
93           When pcretest is built, a configuration  option  can  specify  that  it
94           should  be  linked  with the libreadline library. When this is done, if
95           the input is from a terminal, it is read using the readline() function.
96           This  provides line-editing and history facilities. The output from the
97           -help option states whether or not readline() will be used.
98    
99           The program handles any number of sets of input on a single input file.
100           Each  set starts with a regular expression, and continues with any num-
101           ber of data lines to be matched against the pattern.
102    
103           Each data line is matched separately and independently. If you want  to
104           do multi-line matches, you have to use the \n escape sequence (or \r or
105           \r\n, etc., depending on the newline setting) in a single line of input
106           to  encode  the  newline  sequences. There is no limit on the length of
107           data lines; the input buffer is automatically extended  if  it  is  too
108           small.
109    
110           An  empty  line signals the end of the data lines, at which point a new
111           regular expression is read. The regular expressions are given  enclosed
112           in any non-alphanumeric delimiters other than backslash, for example:
113    
114             /(a|bc)x+yz/
115    
116           White  space before the initial delimiter is ignored. A regular expres-
117           sion may be continued over several input lines, in which case the  new-
118           line  characters  are included within it. It is possible to include the
119           delimiter within the pattern by escaping it, for example
120    
121             /abc\/def/
122    
123           If you do so, the escape and the delimiter form part  of  the  pattern,
124           but  since delimiters are always non-alphanumeric, this does not affect
125           its interpretation.  If the terminating delimiter is  immediately  fol-
126           lowed by a backslash, for example,
127    
128             /abc/\
129    
130           then  a  backslash  is added to the end of the pattern. This is done to
131           provide a way of testing the error condition that arises if  a  pattern
132           finishes with a backslash, because
133    
134             /abc\/
135    
136           is  interpreted as the first line of a pattern that starts with "abc/",
137           causing pcretest to read the next line as a continuation of the regular
138           expression.
139    
140    
141    PATTERN MODIFIERS
142    
143           A  pattern may be followed by any number of modifiers, which are mostly
144           single characters. Following Perl usage, these are  referred  to  below
145           as,  for  example,  "the /i modifier", even though the delimiter of the
146           pattern need not always be a slash, and no slash is used  when  writing
147           modifiers.  Whitespace  may  appear between the final pattern delimiter
148           and the first modifier, and between the modifiers themselves.
149    
150           The /i, /m, /s, and /x modifiers set the PCRE_CASELESS, PCRE_MULTILINE,
151           PCRE_DOTALL,  or  PCRE_EXTENDED  options,  respectively, when pcre_com-
152           pile() is called. These four modifier letters have the same  effect  as
153           they do in Perl. For example:
154    
155             /caseless/i
156    
157           The following table shows additional modifiers for setting PCRE options
158           that do not correspond to anything in Perl:
159    
160             /A              PCRE_ANCHORED
161             /C              PCRE_AUTO_CALLOUT
162             /E              PCRE_DOLLAR_ENDONLY
163             /f              PCRE_FIRSTLINE
164             /J              PCRE_DUPNAMES
165             /N              PCRE_NO_AUTO_CAPTURE
166             /U              PCRE_UNGREEDY
167             /X              PCRE_EXTRA
168             /<JS>           PCRE_JAVASCRIPT_COMPAT
169             /<cr>           PCRE_NEWLINE_CR
170             /<lf>           PCRE_NEWLINE_LF
171             /<crlf>         PCRE_NEWLINE_CRLF
172             /<anycrlf>      PCRE_NEWLINE_ANYCRLF
173             /<any>          PCRE_NEWLINE_ANY
174             /<bsr_anycrlf>  PCRE_BSR_ANYCRLF
175             /<bsr_unicode>  PCRE_BSR_UNICODE
176    
177           Those specifying line ending sequences are literal  strings  as  shown,
178           but  the  letters  can  be  in either case. This example sets multiline
179           matching with CRLF as the line ending sequence:
180    
181             /^abc/m<crlf>
182    
183           Details of the meanings of these PCRE options are given in the  pcreapi
184           documentation.
185    
186       Finding all matches in a string
187    
188           Searching  for  all  possible matches within each subject string can be
189           requested by the /g or /G modifier. After  finding  a  match,  PCRE  is
190           called again to search the remainder of the subject string. The differ-
191           ence between /g and /G is that the former uses the startoffset argument
192           to  pcre_exec()  to  start  searching  at a new point within the entire
193           string (which is in effect what Perl does), whereas the  latter  passes
194           over  a  shortened  substring.  This makes a difference to the matching
195           process if the pattern begins with a lookbehind assertion (including \b
196           or \B).
197    
198           If  any  call  to  pcre_exec()  in a /g or /G sequence matches an empty
199           string, the next  call  is  done  with  the  PCRE_NOTEMPTY_ATSTART  and
200           PCRE_ANCHORED  flags  set  in  order  to search for another, non-empty,
201           match at the same point. If this second match fails, the  start  offset
202           is  advanced  by  one  character, and the normal match is retried. This
203           imitates the way Perl handles such cases when using the /g modifier  or
204           the split() function.
205    
206       Other modifiers
207    
208           There are yet more modifiers for controlling the way pcretest operates.
209    
210           The  /+ modifier requests that as well as outputting the substring that
211           matched the entire pattern, pcretest  should  in  addition  output  the
212           remainder  of  the  subject  string. This is useful for tests where the
213           subject contains multiple copies of the same substring.
214    
215           The /B modifier is a debugging feature. It requests that pcretest  out-
216           put  a representation of the compiled byte code after compilation. Nor-
217           mally this information contains length and offset values;  however,  if
218           /Z  is also present, this data is replaced by spaces. This is a special
219           feature for use in the automatic test scripts; it ensures that the same
220           output is generated for different internal link sizes.
221    
222           The  /L modifier must be followed directly by the name of a locale, for
223           example,
224    
225             /pattern/Lfr_FR
226    
227           For this reason, it must be the last modifier. The given locale is set,
228           pcre_maketables()  is called to build a set of character tables for the
229           locale, and this is then passed to pcre_compile()  when  compiling  the
230           regular  expression.  Without  an  /L  modifier,  NULL is passed as the
231           tables pointer; that is, /L applies only to the expression on which  it
232           appears.
233    
234           The  /I  modifier  requests  that pcretest output information about the
235           compiled pattern (whether it is anchored, has a fixed first  character,
236           and  so  on). It does this by calling pcre_fullinfo() after compiling a
237           pattern. If the pattern is studied, the results of that are  also  out-
238           put.
239    
240           The  /D modifier is a PCRE debugging feature, and is equivalent to /BI,
241           that is, both the /B and the /I modifiers.
242    
243           The /F modifier causes pcretest to flip the byte order of the fields in
244           the  compiled  pattern  that  contain  2-byte  and 4-byte numbers. This
245           facility is for testing the feature in PCRE that allows it  to  execute
246           patterns that were compiled on a host with a different endianness. This
247           feature is not available when the POSIX  interface  to  PCRE  is  being
248           used,  that is, when the /P pattern modifier is specified. See also the
249           section about saving and reloading compiled patterns below.
250    
251           The /S modifier causes pcre_study() to be called after  the  expression
252           has been compiled, and the results used when the expression is matched.
253    
254           The  /M  modifier causes the size of memory block used to hold the com-
255           piled pattern to be output.
256    
257           The /P modifier causes pcretest to call PCRE via the POSIX wrapper  API
258           rather  than  its  native  API.  When this is done, all other modifiers
259           except /i, /m, and /+ are ignored. REG_ICASE is set if /i  is  present,
260           and  REG_NEWLINE  is  set if /m is present. The wrapper functions force
261           PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set.
262    
263           The /8 modifier causes pcretest to call PCRE with the PCRE_UTF8  option
264           set.  This  turns on support for UTF-8 character handling in PCRE, pro-
265           vided that it was compiled with this  support  enabled.  This  modifier
266           also causes any non-printing characters in output strings to be printed
267           using the \x{hh...} notation if they are valid UTF-8 sequences.
268    
269           If the /? modifier  is  used  with  /8,  it  causes  pcretest  to  call
270           pcre_compile()  with  the  PCRE_NO_UTF8_CHECK  option,  to suppress the
271           checking of the string for UTF-8 validity.
272    
273    
274    DATA LINES
275    
276           Before each data line is passed to pcre_exec(),  leading  and  trailing
277           whitespace  is  removed,  and it is then scanned for \ escapes. Some of
278           these are pretty esoteric features, intended for checking out  some  of
279           the  more  complicated features of PCRE. If you are just testing "ordi-
280           nary" regular expressions, you probably don't need any  of  these.  The
281           following escapes are recognized:
282    
283             \a         alarm (BEL, \x07)
284             \b         backspace (\x08)
285             \e         escape (\x27)
286             \f         formfeed (\x0c)
287             \n         newline (\x0a)
288             \qdd       set the PCRE_MATCH_LIMIT limit to dd
289                          (any number of digits)
290             \r         carriage return (\x0d)
291             \t         tab (\x09)
292             \v         vertical tab (\x0b)
293             \nnn       octal character (up to 3 octal digits)
294             \xhh       hexadecimal character (up to 2 hex digits)
295             \x{hh...}  hexadecimal character, any number of digits
296                          in UTF-8 mode
297             \A         pass the PCRE_ANCHORED option to pcre_exec()
298                          or pcre_dfa_exec()
299             \B         pass the PCRE_NOTBOL option to pcre_exec()
300                          or pcre_dfa_exec()
301             \Cdd       call pcre_copy_substring() for substring dd
302                          after a successful match (number less than 32)
303             \Cname     call pcre_copy_named_substring() for substring
304                          "name" after a successful match (name termin-
305                          ated by next non alphanumeric character)
306             \C+        show the current captured substrings at callout
307                          time
308             \C-        do not supply a callout function
309             \C!n       return 1 instead of 0 when callout number n is
310                          reached
311             \C!n!m     return 1 instead of 0 when callout number n is
312                          reached for the nth time
313             \C*n       pass the number n (may be negative) as callout
314                          data; this is used as the callout return value
315             \D         use the pcre_dfa_exec() match function
316             \F         only shortest match for pcre_dfa_exec()
317             \Gdd       call pcre_get_substring() for substring dd
318                          after a successful match (number less than 32)
319             \Gname     call pcre_get_named_substring() for substring
320                          "name" after a successful match (name termin-
321                          ated by next non-alphanumeric character)
322             \L         call pcre_get_substringlist() after a
323                          successful match
324             \M         discover the minimum MATCH_LIMIT and
325                          MATCH_LIMIT_RECURSION settings
326             \N         pass the PCRE_NOTEMPTY option to pcre_exec()
327                          or pcre_dfa_exec(); if used twice, pass the
328                          PCRE_NOTEMPTY_ATSTART option
329             \Odd       set the size of the output vector passed to
330                          pcre_exec() to dd (any number of digits)
331             \P         pass the PCRE_PARTIAL_SOFT option to pcre_exec()
332                          or pcre_dfa_exec(); if used twice, pass the
333                          PCRE_PARTIAL_HARD option
334             \Qdd       set the PCRE_MATCH_LIMIT_RECURSION limit to dd
335                          (any number of digits)
336             \R         pass the PCRE_DFA_RESTART option to pcre_dfa_exec()
337             \S         output details of memory get/free calls during matching
338             \Z         pass the PCRE_NOTEOL option to pcre_exec()
339                          or pcre_dfa_exec()
340             \?         pass the PCRE_NO_UTF8_CHECK option to
341                          pcre_exec() or pcre_dfa_exec()
342             \>dd       start the match at offset dd (any number of digits);
343                          this sets the startoffset argument for pcre_exec()
344                          or pcre_dfa_exec()
345             \<cr>      pass the PCRE_NEWLINE_CR option to pcre_exec()
346                          or pcre_dfa_exec()
347             \<lf>      pass the PCRE_NEWLINE_LF option to pcre_exec()
348                          or pcre_dfa_exec()
349             \<crlf>    pass the PCRE_NEWLINE_CRLF option to pcre_exec()
350                          or pcre_dfa_exec()
351             \<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to pcre_exec()
352                          or pcre_dfa_exec()
353             \<any>     pass the PCRE_NEWLINE_ANY option to pcre_exec()
354                          or pcre_dfa_exec()
355    
356           The  escapes  that  specify  line ending sequences are literal strings,
357           exactly as shown. No more than one newline setting should be present in
358           any data line.
359    
360           A  backslash  followed by anything else just escapes the anything else.
361           If the very last character is a backslash, it is ignored. This gives  a
362           way  of  passing  an empty line as data, since a real empty line termi-
363           nates the data input.
364    
365           If \M is present, pcretest calls pcre_exec() several times,  with  dif-
366           ferent  values  in  the match_limit and match_limit_recursion fields of
367           the pcre_extra data structure, until it finds the minimum  numbers  for
368           each parameter that allow pcre_exec() to complete. The match_limit num-
369           ber is a measure of the amount of backtracking that  takes  place,  and
370           checking it out can be instructive. For most simple matches, the number
371           is quite small, but for patterns with very large  numbers  of  matching
372           possibilities,  it can become large very quickly with increasing length
373           of subject string. The match_limit_recursion number is a measure of how
374           much  stack  (or,  if  PCRE is compiled with NO_RECURSE, how much heap)
375           memory is needed to complete the match attempt.
376    
377           When \O is used, the value specified may be higher or  lower  than  the
378           size set by the -O command line option (or defaulted to 45); \O applies
379           only to the call of pcre_exec() for the line in which it appears.
380    
381           If the /P modifier was present on the pattern, causing the POSIX  wrap-
382           per  API  to  be  used, the only option-setting sequences that have any
383           effect are \B and \Z, causing REG_NOTBOL and REG_NOTEOL,  respectively,
384           to be passed to regexec().
385    
386           The  use of \x{hh...} to represent UTF-8 characters is not dependent on
387           the use of the /8 modifier on the pattern.  It  is  recognized  always.
388           There  may  be  any number of hexadecimal digits inside the braces. The
389           result is from one to six bytes,  encoded  according  to  the  original
390           UTF-8  rules  of  RFC  2279.  This  allows for values in the range 0 to
391           0x7FFFFFFF. Note that not all of those are valid Unicode  code  points,
392           or  indeed  valid  UTF-8 characters according to the later rules in RFC
393           3629.
394    
395    
396    THE ALTERNATIVE MATCHING FUNCTION
397    
398           By  default,  pcretest  uses  the  standard  PCRE  matching   function,
399           pcre_exec() to match each data line. From release 6.0, PCRE supports an
400           alternative matching function, pcre_dfa_test(),  which  operates  in  a
401           different  way,  and has some restrictions. The differences between the
402           two functions are described in the pcrematching documentation.
403    
404           If a data line contains the \D escape sequence, or if the command  line
405           contains  the -dfa option, the alternative matching function is called.
406           This function finds all possible matches at a given point. If, however,
407           the  \F escape sequence is present in the data line, it stops after the
408           first match is found. This is always the shortest possible match.
409    
410    
411    DEFAULT OUTPUT FROM PCRETEST
412    
413           This section describes the output when the  normal  matching  function,
414           pcre_exec(), is being used.
415    
416           When a match succeeds, pcretest outputs the list of captured substrings
417           that pcre_exec() returns, starting with number 0 for  the  string  that
418           matched  the  whole  pattern. Otherwise, it outputs "No match" when the
419           return is PCRE_ERROR_NOMATCH, and "Partial match:" followed by the par-
420           tially  matching substring when pcre_exec() returns PCRE_ERROR_PARTIAL.
421           For any other returns, it outputs the PCRE negative error number.  Here
422           is an example of an interactive pcretest run.
423    
424             $ pcretest
425             PCRE version 7.0 30-Nov-2006
426    
427               re> /^abc(\d+)/
428             data> abc123
429              0: abc123
430              1: 123
431             data> xyz
432             No match
433    
434           Note  that unset capturing substrings that are not followed by one that
435           is set are not returned by pcre_exec(), and are not shown by  pcretest.
436           In  the following example, there are two capturing substrings, but when
437           the first data line is matched, the  second,  unset  substring  is  not
438           shown.  An "internal" unset substring is shown as "<unset>", as for the
439           second data line.
440    
441               re> /(a)|(b)/
442             data> a
443              0: a
444              1: a
445             data> b
446              0: b
447              1: <unset>
448              2: b
449    
450           If the strings contain any non-printing characters, they are output  as
451           \0x  escapes,  or  as \x{...} escapes if the /8 modifier was present on
452           the pattern. See below for the definition of  non-printing  characters.
453           If  the pattern has the /+ modifier, the output for substring 0 is fol-
454           lowed by the the rest of the subject string, identified  by  "0+"  like
455           this:
456    
457               re> /cat/+
458             data> cataract
459              0: cat
460              0+ aract
461    
462           If  the  pattern  has  the /g or /G modifier, the results of successive
463           matching attempts are output in sequence, like this:
464    
465               re> /\Bi(\w\w)/g
466             data> Mississippi
467              0: iss
468              1: ss
469              0: iss
470              1: ss
471              0: ipp
472              1: pp
473    
474           "No match" is output only if the first match attempt fails.
475    
476           If any of the sequences \C, \G, or \L are present in a data  line  that
477           is  successfully  matched,  the substrings extracted by the convenience
478           functions are output with C, G, or L after the string number instead of
479           a colon. This is in addition to the normal full list. The string length
480           (that is, the return from the extraction function) is given  in  paren-
481           theses after each string for \C and \G.
482    
483           Note that whereas patterns can be continued over several lines (a plain
484           ">" prompt is used for continuations), data lines may not. However new-
485           lines  can  be included in data by means of the \n escape (or \r, \r\n,
486           etc., depending on the newline sequence setting).
487    
488    
489    OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION
490    
491           When the alternative matching function, pcre_dfa_exec(),  is  used  (by
492           means  of  the \D escape sequence or the -dfa command line option), the
493           output consists of a list of all the matches that start  at  the  first
494           point in the subject where there is at least one match. For example:
495    
496               re> /(tang|tangerine|tan)/
497             data> yellow tangerine\D
498              0: tangerine
499              1: tang
500              2: tan
501    
502           (Using  the  normal  matching function on this data finds only "tang".)
503           The longest matching string is always given first (and numbered  zero).
504           After a PCRE_ERROR_PARTIAL return, the output is "Partial match:", fol-
505           lowed by the partially matching substring.
506    
507           If /g is present on the pattern, the search for further matches resumes
508           at the end of the longest match. For example:
509    
510               re> /(tang|tangerine|tan)/g
511             data> yellow tangerine and tangy sultana\D
512              0: tangerine
513              1: tang
514              2: tan
515              0: tang
516              1: tan
517              0: tan
518    
519           Since  the  matching  function  does not support substring capture, the
520           escape sequences that are concerned with captured  substrings  are  not
521           relevant.
522    
523    
524    RESTARTING AFTER A PARTIAL MATCH
525    
526           When the alternative matching function has given the PCRE_ERROR_PARTIAL
527           return, indicating that the subject partially matched the pattern,  you
528           can  restart  the match with additional subject data by means of the \R
529           escape sequence. For example:
530    
531               re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/
532             data> 23ja\P\D
533             Partial match: 23ja
534             data> n05\R\D
535              0: n05
536    
537           For further information about partial  matching,  see  the  pcrepartial
538           documentation.
539    
540    
541    CALLOUTS
542    
543           If  the pattern contains any callout requests, pcretest's callout func-
544           tion is called during matching. This works  with  both  matching  func-
545           tions. By default, the called function displays the callout number, the
546           start and current positions in the text at the callout  time,  and  the
547           next pattern item to be tested. For example, the output
548    
549             --->pqrabcdef
550               0    ^  ^     \d
551    
552           indicates  that  callout number 0 occurred for a match attempt starting
553           at the fourth character of the subject string, when the pointer was  at
554           the  seventh  character of the data, and when the next pattern item was
555           \d. Just one circumflex is output if the start  and  current  positions
556           are the same.
557    
558           Callouts numbered 255 are assumed to be automatic callouts, inserted as
559           a result of the /C pattern modifier. In this case, instead  of  showing
560           the  callout  number, the offset in the pattern, preceded by a plus, is
561           output. For example:
562    
563               re> /\d?[A-E]\*/C
564             data> E*
565             --->E*
566              +0 ^      \d?
567              +3 ^      [A-E]
568              +8 ^^     \*
569             +10 ^ ^
570              0: E*
571    
572           The callout function in pcretest returns zero (carry  on  matching)  by
573           default,  but you can use a \C item in a data line (as described above)
574           to change this.
575    
576           Inserting callouts can be helpful when using pcretest to check  compli-
577           cated  regular expressions. For further information about callouts, see
578           the pcrecallout documentation.
579    
580    
581    NON-PRINTING CHARACTERS
582    
583           When pcretest is outputting text in the compiled version of a  pattern,
584           bytes  other  than 32-126 are always treated as non-printing characters
585           are are therefore shown as hex escapes.
586    
587           When pcretest is outputting text that is a matched part  of  a  subject
588           string,  it behaves in the same way, unless a different locale has been
589           set for the  pattern  (using  the  /L  modifier).  In  this  case,  the
590           isprint() function to distinguish printing and non-printing characters.
591    
592    
593    SAVING AND RELOADING COMPILED PATTERNS
594    
595           The  facilities  described  in  this section are not available when the
596           POSIX inteface to PCRE is being used, that is, when the /P pattern mod-
597           ifier is specified.
598    
599           When the POSIX interface is not in use, you can cause pcretest to write
600           a compiled pattern to a file, by following the modifiers with >  and  a
601           file name.  For example:
602    
603             /pattern/im >/some/file
604    
605           See  the pcreprecompile documentation for a discussion about saving and
606           re-using compiled patterns.
607    
608           The data that is written is binary.  The  first  eight  bytes  are  the
609           length  of  the  compiled  pattern  data  followed by the length of the
610           optional study data, each written as four  bytes  in  big-endian  order
611           (most  significant  byte  first). If there is no study data (either the
612           pattern was not studied, or studying did not return any data), the sec-
613           ond  length  is  zero. The lengths are followed by an exact copy of the
614           compiled pattern. If there is additional study data, this follows imme-
615           diately  after  the  compiled pattern. After writing the file, pcretest
616           expects to read a new pattern.
617    
618           A saved pattern can be reloaded into pcretest by specifing < and a file
619           name  instead  of  a pattern. The name of the file must not contain a <
620           character, as otherwise pcretest will interpret the line as  a  pattern
621           delimited by < characters.  For example:
622    
623              re> </some/file
624             Compiled regex loaded from /some/file
625             No study data
626    
627           When  the pattern has been loaded, pcretest proceeds to read data lines
628           in the usual way.
629    
630           You can copy a file written by pcretest to a different host and  reload
631           it  there,  even  if the new host has opposite endianness to the one on
632           which the pattern was compiled. For example, you can compile on an  i86
633           machine and run on a SPARC machine.
634    
635           File  names  for  saving and reloading can be absolute or relative, but
636           note that the shell facility of expanding a file name that starts  with
637           a tilde (~) is not available.
638    
639           The  ability to save and reload files in pcretest is intended for test-
640           ing and experimentation. It is not intended for production use  because
641           only  a  single pattern can be written to a file. Furthermore, there is
642           no facility for supplying  custom  character  tables  for  use  with  a
643           reloaded  pattern.  If  the  original  pattern was compiled with custom
644           tables, an attempt to match a subject string using a  reloaded  pattern
645           is  likely to cause pcretest to crash.  Finally, if you attempt to load
646           a file that is not in the correct format, the result is undefined.
647    
648    
649    SEE ALSO
650    
651           pcre(3), pcreapi(3), pcrecallout(3),  pcrematching(3),  pcrepartial(d),
652           pcrepattern(3), pcreprecompile(3).
653    
654    
655    AUTHOR
656    
657           Philip Hazel
658           University Computing Service
659           Cambridge CB2 3QH, England.
660    
661    
662    REVISION
663    
664           Last updated: 11 September 2009
665           Copyright (c) 1997-2009 University of Cambridge.

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