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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 flag set so that it cannot match an  
 empty string again at the same point. If however, this second match fails, the  
 start offset is advanced by one, and the match is retried. This imitates the  
 way Perl handles such cases when using the /g modifier or the split() function.  
   
 There are a number of other modifiers for controlling the way pcretest  
 operates.  
   
 The /+ modifier requests that as well as outputting the substring that matched  
 the entire pattern, pcretest should in addition output the remainder of the  
 subject string. This is useful for tests where the subject contains multiple  
 copies of the same substring.  
   
 The /L modifier must be followed directly by the name of a locale, for example,  
   
   /pattern/Lfr  
   
 For this reason, it must be the last modifier letter. The given locale is set,  
 pcre_maketables() is called to build a set of character tables for the locale,  
 and this is then passed to pcre_compile() when compiling the regular  
 expression. Without an /L modifier, NULL is passed as the tables pointer; that  
 is, /L applies only to the expression on which it appears.  
   
 The /I modifier requests that pcretest output information about the compiled  
 expression (whether it is anchored, has a fixed first character, and so on). It  
 does this by calling pcre_fullinfo() after compiling an expression, and  
 outputting the information it gets back. If the pattern is studied, the results  
 of that are also output.  
   
 The /D modifier is a PCRE debugging feature, which also assumes /I. It causes  
 the internal form of compiled regular expressions to be output after  
 compilation.  
   
 The /S modifier causes pcre_study() to be called after the expression has been  
 compiled, and the results used when the expression is matched.  
   
 The /M modifier causes the size of memory block used to hold the compiled  
 pattern to be output.  
   
 Finally, the /P modifier causes pcretest to call PCRE via the POSIX wrapper API  
 rather than its native API. When this is done, all other modifiers except /i,  
 /m, and /+ are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is  
 set if /m is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always,  
 and PCRE_DOTALL unless REG_NEWLINE is set.  
   
 Before each data line is passed to pcre_exec(), leading and trailing whitespace  
 is removed, and it is then scanned for \ escapes. The following are recognized:  
   
   \a     alarm (= BEL)  
   \b     backspace  
   \e     escape  
   \f     formfeed  
   \n     newline  
   \r     carriage return  
   \t     tab  
   \v     vertical tab  
   \nnn   octal character (up to 3 octal digits)  
   \xhh   hexadecimal character (up to 2 hex digits)  
   
   \A     pass the PCRE_ANCHORED option to pcre_exec()  
   \B     pass the PCRE_NOTBOL option to pcre_exec()  
   \Cdd   call pcre_copy_substring() for substring dd after a successful match  
            (any decimal number less than 32)  
   \Gdd   call pcre_get_substring() for substring dd after a successful match  
            (any decimal number less than 32)  
   \L     call pcre_get_substringlist() after a successful match  
   \N     pass the PCRE_NOTEMPTY option to pcre_exec()  
   \Odd   set the size of the output vector passed to pcre_exec() to dd  
            (any number of decimal digits)  
   \Z     pass the PCRE_NOTEOL option to pcre_exec()  
   
 A backslash followed by anything else just escapes the anything else. If the  
 very last character is a backslash, it is ignored. This gives a way of passing  
 an empty line as data, since a real empty line terminates the data input.  
   
 If /P was present on the regex, causing the POSIX wrapper API to be used, only  
 \B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to  
 regexec() respectively.  
   
 When a match succeeds, pcretest outputs the list of captured substrings that  
 pcre_exec() returns, starting with number 0 for the string that matched the  
 whole pattern. Here is an example of an interactive pcretest run.  
   
   $ pcretest  
   PCRE version 2.06 08-Jun-1999  
   
     re> /^abc(\d+)/  
   data> abc123  
    0: abc123  
    1: 123  
   data> xyz  
   No match  
   
 If the strings contain any non-printing characters, they are output as \0x  
 escapes. If the pattern has the /+ modifier, then the output for substring 0 is  
 followed by the the rest of the subject string, identified by "0+" like this:  
   
     re> /cat/+  
   data> cataract  
    0: cat  
    0+ aract  
   
 If the pattern has the /g or /G modifier, the results of successive matching  
 attempts are output in sequence, like this:  
   
     re> /\Bi(\w\w)/g  
   data> Mississippi  
    0: iss  
    1: ss  
    0: iss  
    1: ss  
    0: ipp  
    1: pp  
   
 "No match" is output only if the first match attempt fails.  
   
 If any of \C, \G, or \L are present in a data line that is successfully  
 matched, the substrings extracted by the convenience functions are output with  
 C, G, or L after the string number instead of a colon. This is in addition to  
 the normal full list. The string length (that is, the return from the  
 extraction function) is given in parentheses after each string for \C and \G.  
   
 Note that while patterns can be continued over several lines (a plain ">"  
 prompt is used for continuations), data lines may not. However newlines can be  
 included in data by means of the \n escape.  
   
 If the -p option is given to pcretest, it is equivalent to adding /P to each  
 regular expression: the POSIX wrapper API is used to call PCRE. None of the  
 following flags has any effect in this case.  
   
 If the option -d is given to pcretest, it is equivalent to adding /D to each  
 regular expression: the internal form is output after compilation.  
   
 If the option -i is given to pcretest, it is equivalent to adding /I to each  
 regular expression: information about the compiled pattern is given after  
 compilation.  
   
 If the option -m is given to pcretest, it outputs the size of each compiled  
 pattern after it has been compiled. It is equivalent to adding /M to each  
 regular expression. For compatibility with earlier versions of pcretest, -s is  
 a synonym for -m.  
   
 If the -t option is given, each compile, study, and match is run 20000 times  
 while being timed, and the resulting time per compile or match is output in  
 milliseconds. Do not set -t with -s, because you will then get the size output  
 20000 times and the timing will be distorted. If you want to change the number  
 of repetitions used for timing, edit the definition of LOOPREPEAT at the top of  
 pcretest.c  
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           The program handles any number of sets of input on a single input file.
89           Each set starts with a regular expression, and continues with any  num-
90           ber of data lines to be matched against the pattern.
91    
92           Each  data line is matched separately and independently. If you want to
93           do multi-line matches, you have to use the \n escape sequence (or \r or
94           \r\n, etc., depending on the newline setting) in a single line of input
95           to encode the newline sequences. There is no limit  on  the  length  of
96           data  lines;  the  input  buffer is automatically extended if it is too
97           small.
98    
99           An empty line signals the end of the data lines, at which point  a  new
100           regular  expression is read. The regular expressions are given enclosed
101           in any non-alphanumeric delimiters other than backslash, for example:
102    
103             /(a|bc)x+yz/
104    
105           White space before the initial delimiter is ignored. A regular  expres-
106           sion  may be continued over several input lines, in which case the new-
107           line characters are included within it. It is possible to  include  the
108           delimiter within the pattern by escaping it, for example
109    
110             /abc\/def/
111    
112           If  you  do  so, the escape and the delimiter form part of the pattern,
113           but since delimiters are always non-alphanumeric, this does not  affect
114           its  interpretation.   If the terminating delimiter is immediately fol-
115           lowed by a backslash, for example,
116    
117             /abc/\
118    
119           then a backslash is added to the end of the pattern. This  is  done  to
120           provide  a  way of testing the error condition that arises if a pattern
121           finishes with a backslash, because
122    
123             /abc\/
124    
125           is interpreted as the first line of a pattern that starts with  "abc/",
126           causing pcretest to read the next line as a continuation of the regular
127           expression.
128    
129    
130    PATTERN MODIFIERS
131    
132           A pattern may be followed by any number of modifiers, which are  mostly
133           single  characters.  Following  Perl usage, these are referred to below
134           as, for example, "the /i modifier", even though the  delimiter  of  the
135           pattern  need  not always be a slash, and no slash is used when writing
136           modifiers. Whitespace may appear between the  final  pattern  delimiter
137           and the first modifier, and between the modifiers themselves.
138    
139           The /i, /m, /s, and /x modifiers set the PCRE_CASELESS, PCRE_MULTILINE,
140           PCRE_DOTALL, or PCRE_EXTENDED  options,  respectively,  when  pcre_com-
141           pile()  is  called. These four modifier letters have the same effect as
142           they do in Perl. For example:
143    
144             /caseless/i
145    
146           The following table shows additional modifiers for setting PCRE options
147           that do not correspond to anything in Perl:
148    
149             /A       PCRE_ANCHORED
150             /C       PCRE_AUTO_CALLOUT
151             /E       PCRE_DOLLAR_ENDONLY
152             /f       PCRE_FIRSTLINE
153             /J       PCRE_DUPNAMES
154             /N       PCRE_NO_AUTO_CAPTURE
155             /U       PCRE_UNGREEDY
156             /X       PCRE_EXTRA
157             /<cr>    PCRE_NEWLINE_CR
158             /<lf>    PCRE_NEWLINE_LF
159             /<crlf>  PCRE_NEWLINE_CRLF
160             /<any>   PCRE_NEWLINE_ANY
161    
162           Those  specifying  line ending sequencess are literal strings as shown.
163           This example sets multiline matching  with  CRLF  as  the  line  ending
164           sequence:
165    
166             /^abc/m<crlf>
167    
168           Details  of the meanings of these PCRE options are given in the pcreapi
169           documentation.
170    
171       Finding all matches in a string
172    
173           Searching for all possible matches within each subject  string  can  be
174           requested  by  the  /g  or  /G modifier. After finding a match, PCRE is
175           called again to search the remainder of the subject string. The differ-
176           ence between /g and /G is that the former uses the startoffset argument
177           to pcre_exec() to start searching at a  new  point  within  the  entire
178           string  (which  is in effect what Perl does), whereas the latter passes
179           over a shortened substring. This makes a  difference  to  the  matching
180           process if the pattern begins with a lookbehind assertion (including \b
181           or \B).
182    
183           If any call to pcre_exec() in a /g or  /G  sequence  matches  an  empty
184           string,  the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
185           flags set in order to search for another, non-empty, match at the  same
186           point.   If  this  second  match fails, the start offset is advanced by
187           one, and the normal match is retried. This imitates the way  Perl  han-
188           dles such cases when using the /g modifier or the split() function.
189    
190       Other modifiers
191    
192           There are yet more modifiers for controlling the way pcretest operates.
193    
194           The /+ modifier requests that as well as outputting the substring  that
195           matched  the  entire  pattern,  pcretest  should in addition output the
196           remainder of the subject string. This is useful  for  tests  where  the
197           subject contains multiple copies of the same substring.
198    
199           The  /B modifier is a debugging feature. It requests that pcretest out-
200           put a representation of the compiled byte code after compilation.
201    
202           The /L modifier must be followed directly by the name of a locale,  for
203           example,
204    
205             /pattern/Lfr_FR
206    
207           For this reason, it must be the last modifier. The given locale is set,
208           pcre_maketables() is called to build a set of character tables for  the
209           locale,  and  this  is then passed to pcre_compile() when compiling the
210           regular expression. Without an /L  modifier,  NULL  is  passed  as  the
211           tables  pointer; that is, /L applies only to the expression on which it
212           appears.
213    
214           The /I modifier requests that pcretest  output  information  about  the
215           compiled  pattern (whether it is anchored, has a fixed first character,
216           and so on). It does this by calling pcre_fullinfo() after  compiling  a
217           pattern.  If  the pattern is studied, the results of that are also out-
218           put.
219    
220           The /D modifier is a PCRE debugging feature, and is equivalent to  /BI,
221           that is, both the /B and the /I modifiers.
222    
223           The /F modifier causes pcretest to flip the byte order of the fields in
224           the compiled pattern that  contain  2-byte  and  4-byte  numbers.  This
225           facility  is  for testing the feature in PCRE that allows it to execute
226           patterns that were compiled on a host with a different endianness. This
227           feature  is  not  available  when  the POSIX interface to PCRE is being
228           used, that is, when the /P pattern modifier is specified. See also  the
229           section about saving and reloading compiled patterns below.
230    
231           The  /S  modifier causes pcre_study() to be called after the expression
232           has been compiled, and the results used when the expression is matched.
233    
234           The  /M  modifier causes the size of memory block used to hold the com-
235           piled pattern to be output.
236    
237           The /P modifier causes pcretest to call PCRE via the POSIX wrapper  API
238           rather  than  its  native  API.  When this is done, all other modifiers
239           except /i, /m, and /+ are ignored. REG_ICASE is set if /i  is  present,
240           and  REG_NEWLINE  is  set if /m is present. The wrapper functions force
241           PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is  set.
242    
243           The  /8 modifier causes pcretest to call PCRE with the PCRE_UTF8 option
244           set. This turns on support for UTF-8 character handling in  PCRE,  pro-
245           vided  that  it  was  compiled with this support enabled. This modifier
246           also causes any non-printing characters in output strings to be printed
247           using the \x{hh...} notation if they are valid UTF-8 sequences.
248    
249           If  the  /?  modifier  is  used  with  /8,  it  causes pcretest to call
250           pcre_compile() with the  PCRE_NO_UTF8_CHECK  option,  to  suppress  the
251           checking of the string for UTF-8 validity.
252    
253    
254    DATA LINES
255    
256           Before  each  data  line is passed to pcre_exec(), leading and trailing
257           whitespace is removed, and it is then scanned for \  escapes.  Some  of
258           these  are  pretty esoteric features, intended for checking out some of
259           the more complicated features of PCRE. If you are just  testing  "ordi-
260           nary"  regular  expressions,  you probably don't need any of these. The
261           following escapes are recognized:
262    
263             \a         alarm (BEL, \x07)
264             \b         backspace (\x08)
265             \e         escape (\x27)
266             \f         formfeed (\x0c)
267             \n         newline (\x0a)
268             \qdd       set the PCRE_MATCH_LIMIT limit to dd
269                          (any number of digits)
270             \r         carriage return (\x0d)
271             \t         tab (\x09)
272             \v         vertical tab (\x0b)
273             \nnn       octal character (up to 3 octal digits)
274             \xhh       hexadecimal character (up to 2 hex digits)
275             \x{hh...}  hexadecimal character, any number of digits
276                          in UTF-8 mode
277             \A         pass the PCRE_ANCHORED option to pcre_exec()
278                          or pcre_dfa_exec()
279             \B         pass the PCRE_NOTBOL option to pcre_exec()
280                          or pcre_dfa_exec()
281             \Cdd       call pcre_copy_substring() for substring dd
282                          after a successful match (number less than 32)
283             \Cname     call pcre_copy_named_substring() for substring
284                          "name" after a successful match (name termin-
285                          ated by next non alphanumeric character)
286             \C+        show the current captured substrings at callout
287                          time
288             \C-        do not supply a callout function
289             \C!n       return 1 instead of 0 when callout number n is
290                          reached
291             \C!n!m     return 1 instead of 0 when callout number n is
292                          reached for the nth time
293             \C*n       pass the number n (may be negative) as callout
294                          data; this is used as the callout return value
295             \D         use the pcre_dfa_exec() match function
296             \F         only shortest match for pcre_dfa_exec()
297             \Gdd       call pcre_get_substring() for substring dd
298                          after a successful match (number less than 32)
299             \Gname     call pcre_get_named_substring() for substring
300                          "name" after a successful match (name termin-
301                          ated by next non-alphanumeric character)
302             \L         call pcre_get_substringlist() after a
303                          successful match
304             \M         discover the minimum MATCH_LIMIT and
305                          MATCH_LIMIT_RECURSION settings
306             \N         pass the PCRE_NOTEMPTY option to pcre_exec()
307                          or pcre_dfa_exec()
308             \Odd       set the size of the output vector passed to
309                          pcre_exec() to dd (any number of digits)
310             \P         pass the PCRE_PARTIAL option to pcre_exec()
311                          or pcre_dfa_exec()
312             \Qdd       set the PCRE_MATCH_LIMIT_RECURSION limit to dd
313                          (any number of digits)
314             \R         pass the PCRE_DFA_RESTART option to pcre_dfa_exec()
315             \S         output details of memory get/free calls during matching
316             \Z         pass the PCRE_NOTEOL option to pcre_exec()
317                          or pcre_dfa_exec()
318             \?         pass the PCRE_NO_UTF8_CHECK option to
319                          pcre_exec() or pcre_dfa_exec()
320             \>dd       start the match at offset dd (any number of digits);
321                          this sets the startoffset argument for pcre_exec()
322                          or pcre_dfa_exec()
323             \<cr>      pass the PCRE_NEWLINE_CR option to pcre_exec()
324                          or pcre_dfa_exec()
325             \<lf>      pass the PCRE_NEWLINE_LF option to pcre_exec()
326                          or pcre_dfa_exec()
327             \<crlf>    pass the PCRE_NEWLINE_CRLF option to pcre_exec()
328                          or pcre_dfa_exec()
329             \<any>     pass the PCRE_NEWLINE_ANY option to pcre_exec()
330                          or pcre_dfa_exec()
331    
332           The escapes that specify line ending  sequences  are  literal  strings,
333           exactly as shown. No more than one newline setting should be present in
334           any data line.
335    
336           A backslash followed by anything else just escapes the  anything  else.
337           If  the very last character is a backslash, it is ignored. This gives a
338           way of passing an empty line as data, since a real  empty  line  termi-
339           nates the data input.
340    
341           If  \M  is present, pcretest calls pcre_exec() several times, with dif-
342           ferent values in the match_limit and  match_limit_recursion  fields  of
343           the  pcre_extra  data structure, until it finds the minimum numbers for
344           each parameter that allow pcre_exec() to complete. The match_limit num-
345           ber  is  a  measure of the amount of backtracking that takes place, and
346           checking it out can be instructive. For most simple matches, the number
347           is  quite  small,  but for patterns with very large numbers of matching
348           possibilities, it can become large very quickly with increasing  length
349           of subject string. The match_limit_recursion number is a measure of how
350           much stack (or, if PCRE is compiled with  NO_RECURSE,  how  much  heap)
351           memory is needed to complete the match attempt.
352    
353           When  \O  is  used, the value specified may be higher or lower than the
354           size set by the -O command line option (or defaulted to 45); \O applies
355           only to the call of pcre_exec() for the line in which it appears.
356    
357           If  the /P modifier was present on the pattern, causing the POSIX wrap-
358           per API to be used, the only option-setting  sequences  that  have  any
359           effect  are \B and \Z, causing REG_NOTBOL and REG_NOTEOL, respectively,
360           to be passed to regexec().
361    
362           The use of \x{hh...} to represent UTF-8 characters is not dependent  on
363           the  use  of  the  /8 modifier on the pattern. It is recognized always.
364           There may be any number of hexadecimal digits inside  the  braces.  The
365           result  is from one to six bytes, encoded according to the UTF-8 rules.
366    
367    
368    THE ALTERNATIVE MATCHING FUNCTION
369    
370           By  default,  pcretest  uses  the  standard  PCRE  matching   function,
371           pcre_exec() to match each data line. From release 6.0, PCRE supports an
372           alternative matching function, pcre_dfa_test(),  which  operates  in  a
373           different  way,  and has some restrictions. The differences between the
374           two functions are described in the pcrematching documentation.
375    
376           If a data line contains the \D escape sequence, or if the command  line
377           contains  the -dfa option, the alternative matching function is called.
378           This function finds all possible matches at a given point. If, however,
379           the  \F escape sequence is present in the data line, it stops after the
380           first match is found. This is always the shortest possible match.
381    
382    
383    DEFAULT OUTPUT FROM PCRETEST
384    
385           This section describes the output when the  normal  matching  function,
386           pcre_exec(), is being used.
387    
388           When a match succeeds, pcretest outputs the list of captured substrings
389           that pcre_exec() returns, starting with number 0 for  the  string  that
390           matched the whole pattern. Otherwise, it outputs "No match" or "Partial
391           match" when pcre_exec() returns PCRE_ERROR_NOMATCH  or  PCRE_ERROR_PAR-
392           TIAL,  respectively, and otherwise the PCRE negative error number. Here
393           is an example of an interactive pcretest run.
394    
395             $ pcretest
396             PCRE version 7.0 30-Nov-2006
397    
398               re> /^abc(\d+)/
399             data> abc123
400              0: abc123
401              1: 123
402             data> xyz
403             No match
404    
405           If the strings contain any non-printing characters, they are output  as
406           \0x  escapes,  or  as \x{...} escapes if the /8 modifier was present on
407           the pattern. See below for the definition of  non-printing  characters.
408           If  the pattern has the /+ modifier, the output for substring 0 is fol-
409           lowed by the the rest of the subject string, identified  by  "0+"  like
410           this:
411    
412               re> /cat/+
413             data> cataract
414              0: cat
415              0+ aract
416    
417           If  the  pattern  has  the /g or /G modifier, the results of successive
418           matching attempts are output in sequence, like this:
419    
420               re> /\Bi(\w\w)/g
421             data> Mississippi
422              0: iss
423              1: ss
424              0: iss
425              1: ss
426              0: ipp
427              1: pp
428    
429           "No match" is output only if the first match attempt fails.
430    
431           If any of the sequences \C, \G, or \L are present in a data  line  that
432           is  successfully  matched,  the substrings extracted by the convenience
433           functions are output with C, G, or L after the string number instead of
434           a colon. This is in addition to the normal full list. The string length
435           (that is, the return from the extraction function) is given  in  paren-
436           theses after each string for \C and \G.
437    
438           Note that whereas patterns can be continued over several lines (a plain
439           ">" prompt is used for continuations), data lines may not. However new-
440           lines  can  be included in data by means of the \n escape (or \r, \r\n,
441           etc., depending on the newline sequence setting).
442    
443    
444    OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION
445    
446           When the alternative matching function, pcre_dfa_exec(),  is  used  (by
447           means  of  the \D escape sequence or the -dfa command line option), the
448           output consists of a list of all the matches that start  at  the  first
449           point in the subject where there is at least one match. For example:
450    
451               re> /(tang|tangerine|tan)/
452             data> yellow tangerine\D
453              0: tangerine
454              1: tang
455              2: tan
456    
457           (Using  the  normal  matching function on this data finds only "tang".)
458           The longest matching string is always given first (and numbered  zero).
459    
460           If /g is present on the pattern, the search for further matches resumes
461           at the end of the longest match. For example:
462    
463               re> /(tang|tangerine|tan)/g
464             data> yellow tangerine and tangy sultana\D
465              0: tangerine
466              1: tang
467              2: tan
468              0: tang
469              1: tan
470              0: tan
471    
472           Since the matching function does not  support  substring  capture,  the
473           escape  sequences  that  are concerned with captured substrings are not
474           relevant.
475    
476    
477    RESTARTING AFTER A PARTIAL MATCH
478    
479           When the alternative matching function has given the PCRE_ERROR_PARTIAL
480           return,  indicating that the subject partially matched the pattern, you
481           can restart the match with additional subject data by means of  the  \R
482           escape sequence. For example:
483    
484               re> /^?(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)$/
485             data> 23ja\P\D
486             Partial match: 23ja
487             data> n05\R\D
488              0: n05
489    
490           For  further  information  about  partial matching, see the pcrepartial
491           documentation.
492    
493    
494    CALLOUTS
495    
496           If the pattern contains any callout requests, pcretest's callout  func-
497           tion  is  called  during  matching. This works with both matching func-
498           tions. By default, the called function displays the callout number, the
499           start  and  current  positions in the text at the callout time, and the
500           next pattern item to be tested. For example, the output
501    
502             --->pqrabcdef
503               0    ^  ^     \d
504    
505           indicates that callout number 0 occurred for a match  attempt  starting
506           at  the fourth character of the subject string, when the pointer was at
507           the seventh character of the data, and when the next pattern  item  was
508           \d.  Just  one  circumflex is output if the start and current positions
509           are the same.
510    
511           Callouts numbered 255 are assumed to be automatic callouts, inserted as
512           a  result  of the /C pattern modifier. In this case, instead of showing
513           the callout number, the offset in the pattern, preceded by a  plus,  is
514           output. For example:
515    
516               re> /\d?[A-E]\*/C
517             data> E*
518             --->E*
519              +0 ^      \d?
520              +3 ^      [A-E]
521              +8 ^^     \*
522             +10 ^ ^
523              0: E*
524    
525           The  callout  function  in pcretest returns zero (carry on matching) by
526           default, but you can use a \C item in a data line (as described  above)
527           to change this.
528    
529           Inserting  callouts can be helpful when using pcretest to check compli-
530           cated regular expressions. For further information about callouts,  see
531           the pcrecallout documentation.
532    
533    
534    NON-PRINTING CHARACTERS
535    
536           When  pcretest is outputting text in the compiled version of a pattern,
537           bytes other than 32-126 are always treated as  non-printing  characters
538           are are therefore shown as hex escapes.
539    
540           When  pcretest  is  outputting text that is a matched part of a subject
541           string, it behaves in the same way, unless a different locale has  been
542           set  for  the  pattern  (using  the  /L  modifier).  In  this case, the
543           isprint() function to distinguish printing and non-printing characters.
544    
545    
546    SAVING AND RELOADING COMPILED PATTERNS
547    
548           The  facilities  described  in  this section are not available when the
549           POSIX inteface to PCRE is being used, that is, when the /P pattern mod-
550           ifier is specified.
551    
552           When the POSIX interface is not in use, you can cause pcretest to write
553           a compiled pattern to a file, by following the modifiers with >  and  a
554           file name.  For example:
555    
556             /pattern/im >/some/file
557    
558           See  the pcreprecompile documentation for a discussion about saving and
559           re-using compiled patterns.
560    
561           The data that is written is binary.  The  first  eight  bytes  are  the
562           length  of  the  compiled  pattern  data  followed by the length of the
563           optional study data, each written as four  bytes  in  big-endian  order
564           (most  significant  byte  first). If there is no study data (either the
565           pattern was not studied, or studying did not return any data), the sec-
566           ond  length  is  zero. The lengths are followed by an exact copy of the
567           compiled pattern. If there is additional study data, this follows imme-
568           diately  after  the  compiled pattern. After writing the file, pcretest
569           expects to read a new pattern.
570    
571           A saved pattern can be reloaded into pcretest by specifing < and a file
572           name  instead  of  a pattern. The name of the file must not contain a <
573           character, as otherwise pcretest will interpret the line as  a  pattern
574           delimited by < characters.  For example:
575    
576              re> </some/file
577             Compiled regex loaded from /some/file
578             No study data
579    
580           When  the pattern has been loaded, pcretest proceeds to read data lines
581           in the usual way.
582    
583           You can copy a file written by pcretest to a different host and  reload
584           it  there,  even  if the new host has opposite endianness to the one on
585           which the pattern was compiled. For example, you can compile on an  i86
586           machine and run on a SPARC machine.
587    
588           File  names  for  saving and reloading can be absolute or relative, but
589           note that the shell facility of expanding a file name that starts  with
590           a tilde (~) is not available.
591    
592           The  ability to save and reload files in pcretest is intended for test-
593           ing and experimentation. It is not intended for production use  because
594           only  a  single pattern can be written to a file. Furthermore, there is
595           no facility for supplying  custom  character  tables  for  use  with  a
596           reloaded  pattern.  If  the  original  pattern was compiled with custom
597           tables, an attempt to match a subject string using a  reloaded  pattern
598           is  likely to cause pcretest to crash.  Finally, if you attempt to load
599           a file that is not in the correct format, the result is undefined.
600    
601    
602    SEE ALSO
603    
604           pcre(3), pcreapi(3), pcrecallout(3),  pcrematching(3),  pcrepartial(d),
605           pcrepattern(3), pcreprecompile(3).
606    
607    
608    AUTHOR
609    
610           Philip Hazel
611           University Computing Service,
612           Cambridge CB2 3QH, England.
613    
614    Last updated: 30 November 2006
615    Copyright (c) 1997-2006 University of Cambridge.

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