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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] [input file [output file]]
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. The input  for  pcretest  is  a
18           sequence  of  regular expression patterns and strings to be matched, as
19           described below. The output shows the result of each match. Options  on
20           the command line and the patterns control PCRE options and exactly what
21           is output.
22    
23    
24    COMMAND LINE OPTIONS
25    
26           -b        Behave as if each pattern has the /B (show byte  code)  modi-
27                     fier; the internal form is output after compilation.
28    
29           -C        Output the version number of the PCRE library, and all avail-
30                     able  information  about  the  optional  features  that   are
31                     included, and then exit.
32    
33           -d        Behave  as  if  each pattern has the /D (debug) modifier; the
34                     internal form and information about the compiled  pattern  is
35                     output after compilation; -d is equivalent to -b -i.
36    
37           -dfa      Behave  as if each data line contains the \D escape sequence;
38                     this    causes    the    alternative    matching    function,
39                     pcre_dfa_exec(),   to   be   used  instead  of  the  standard
40                     pcre_exec() function (more detail is given below).
41    
42           -help     Output a brief summary these options and then exit.
43    
44           -i        Behave as if each pattern has the  /I  modifier;  information
45                     about the compiled pattern is given after compilation.
46    
47           -M        Behave  as if each data line contains the \M escape sequence;
48                     this causes PCRE to  discover  the  minimum  MATCH_LIMIT  and
49                     MATCH_LIMIT_RECURSION settings by calling pcre_exec() repeat-
50                     edly with different limits.
51    
52           -m        Output the size of each compiled pattern after  it  has  been
53                     compiled.  This  is  equivalent  to adding /M to each regular
54                     expression.
55    
56           -o osize  Set the number of elements in the output vector that is  used
57                     when  calling pcre_exec() or pcre_dfa_exec() to be osize. The
58                     default value is 45, which is enough for 14 capturing  subex-
59                     pressions   for  pcre_exec()  or  22  different  matches  for
60                     pcre_dfa_exec(). The vector size can be changed for  individ-
61                     ual  matching  calls  by  including  \O in the data line (see
62                     below).
63    
64           -p        Behave as if each pattern has  the  /P  modifier;  the  POSIX
65                     wrapper  API  is used to call PCRE. None of the other options
66                     has any effect when -p is set.
67    
68           -q        Do not output the version number of pcretest at the start  of
69                     execution.
70    
71           -S size   On  Unix-like  systems, set the size of the run-time stack to
72                     size megabytes.
73    
74           -s or -s+ Behave as if each pattern  has  the  /S  modifier;  in  other
75                     words,  force each pattern to be studied. If -s+ is used, the
76                     PCRE_STUDY_JIT_COMPILE flag is passed to pcre_study(),  caus-
77                     ing  just-in-time  optimization  to be set up if it is avail-
78                     able. If the  /I  or  /D  option  is  present  on  a  pattern
79                     (requesting  output  about the compiled pattern), information
80                     about the result of studying is not included when studying is
81                     caused  only  by  -s  and neither -i nor -d is present on the
82                     command line. This behaviour means that the output from tests
83                     that  are run with and without -s should be identical, except
84                     when options that output information about the actual running
85                     of  a  match are set. The -M, -t, and -tm options, which give
86                     information about resources used, are likely to produce  dif-
87                     ferent  output with and without -s. Output may also differ if
88                     the /C option is present on an individual pattern. This  uses
89                     callouts  to  trace the the matching process, and this may be
90                     different between studied and non-studied  patterns.  If  the
91                     pattern contains (*MARK) items there may also be differences,
92                     for the same reason. The -s command line option can be  over-
93                     ridden  for  specific  patterns  that should never be studied
94                     (see the /S pattern modifier below).
95    
96           -t        Run each compile, study, and match many times with  a  timer,
97                     and  output resulting time per compile or match (in millisec-
98                     onds). Do not set -m with -t, because you will then  get  the
99                     size  output  a  zillion  times,  and the timing will be dis-
100                     torted. You can control the number  of  iterations  that  are
101                     used  for timing by following -t with a number (as a separate
102                     item on the command line). For example, "-t 1000" would iter-
103                     ate 1000 times. The default is to iterate 500000 times.
104    
105           -tm       This is like -t except that it times only the matching phase,
106                     not the compile or study phases.
107    
108    
109    DESCRIPTION
110    
111           If pcretest is given two filename arguments, it reads  from  the  first
112           and writes to the second. If it is given only one filename argument, it
113           reads from that file and writes to stdout.  Otherwise,  it  reads  from
114           stdin  and  writes to stdout, and prompts for each line of input, using
115           "re>" to prompt for regular expressions, and "data>" to prompt for data
116           lines.
117    
118           When  pcretest  is  built,  a  configuration option can specify that it
119           should be linked with the libreadline library. When this  is  done,  if
120           the input is from a terminal, it is read using the readline() function.
121           This provides line-editing and history facilities. The output from  the
122           -help option states whether or not readline() will be used.
123    
124           The program handles any number of sets of input on a single input file.
125           Each set starts with a regular expression, and continues with any  num-
126           ber of data lines to be matched against the pattern.
127    
128           Each  data line is matched separately and independently. If you want to
129           do multi-line matches, you have to use the \n escape sequence (or \r or
130           \r\n, etc., depending on the newline setting) in a single line of input
131           to encode the newline sequences. There is no limit  on  the  length  of
132           data  lines;  the  input  buffer is automatically extended if it is too
133           small.
134    
135           An empty line signals the end of the data lines, at which point  a  new
136           regular  expression is read. The regular expressions are given enclosed
137           in any non-alphanumeric delimiters other than backslash, for example:
138    
139             /(a|bc)x+yz/
140    
141           White space before the initial delimiter is ignored. A regular  expres-
142           sion  may be continued over several input lines, in which case the new-
143           line characters are included within it. It is possible to  include  the
144           delimiter within the pattern by escaping it, for example
145    
146             /abc\/def/
147    
148           If  you  do  so, the escape and the delimiter form part of the pattern,
149           but since delimiters are always non-alphanumeric, this does not  affect
150           its  interpretation.   If the terminating delimiter is immediately fol-
151           lowed by a backslash, for example,
152    
153             /abc/\
154    
155           then a backslash is added to the end of the pattern. This  is  done  to
156           provide  a  way of testing the error condition that arises if a pattern
157           finishes with a backslash, because
158    
159             /abc\/
160    
161           is interpreted as the first line of a pattern that starts with  "abc/",
162           causing pcretest to read the next line as a continuation of the regular
163           expression.
164    
165    
166    PATTERN MODIFIERS
167    
168           A pattern may be followed by any number of modifiers, which are  mostly
169           single  characters.  Following  Perl usage, these are referred to below
170           as, for example, "the /i modifier", even though the  delimiter  of  the
171           pattern  need  not always be a slash, and no slash is used when writing
172           modifiers. White space may appear between the final  pattern  delimiter
173           and the first modifier, and between the modifiers themselves.
174    
175           The /i, /m, /s, and /x modifiers set the PCRE_CASELESS, PCRE_MULTILINE,
176           PCRE_DOTALL, or PCRE_EXTENDED  options,  respectively,  when  pcre_com-
177           pile()  is  called. These four modifier letters have the same effect as
178           they do in Perl. For example:
179    
180             /caseless/i
181    
182           The following table shows additional modifiers for  setting  PCRE  com-
183           pile-time options that do not correspond to anything in Perl:
184    
185             /8              PCRE_UTF8
186             /?              PCRE_NO_UTF8_CHECK
187             /A              PCRE_ANCHORED
188             /C              PCRE_AUTO_CALLOUT
189             /E              PCRE_DOLLAR_ENDONLY
190             /f              PCRE_FIRSTLINE
191             /J              PCRE_DUPNAMES
192             /N              PCRE_NO_AUTO_CAPTURE
193             /U              PCRE_UNGREEDY
194             /W              PCRE_UCP
195             /X              PCRE_EXTRA
196             /Y              PCRE_NO_START_OPTIMIZE
197             /<JS>           PCRE_JAVASCRIPT_COMPAT
198             /<cr>           PCRE_NEWLINE_CR
199             /<lf>           PCRE_NEWLINE_LF
200             /<crlf>         PCRE_NEWLINE_CRLF
201             /<anycrlf>      PCRE_NEWLINE_ANYCRLF
202             /<any>          PCRE_NEWLINE_ANY
203             /<bsr_anycrlf>  PCRE_BSR_ANYCRLF
204             /<bsr_unicode>  PCRE_BSR_UNICODE
205    
206           The  modifiers  that are enclosed in angle brackets are literal strings
207           as shown, including the angle brackets, but the letters within  can  be
208           in  either case.  This example sets multiline matching with CRLF as the
209           line ending sequence:
210    
211             /^abc/m<CRLF>
212    
213           As well as turning on the PCRE_UTF8 option, the /8 modifier also causes
214           any  non-printing  characters in output strings to be printed using the
215           \x{hh...} notation if they are valid UTF-8 sequences. Full  details  of
216           the PCRE options are given in the pcreapi documentation.
217    
218       Finding all matches in a string
219    
220           Searching  for  all  possible matches within each subject string can be
221           requested by the /g or /G modifier. After  finding  a  match,  PCRE  is
222           called again to search the remainder of the subject string. The differ-
223           ence between /g and /G is that the former uses the startoffset argument
224           to  pcre_exec()  to  start  searching  at a new point within the entire
225           string (which is in effect what Perl does), whereas the  latter  passes
226           over  a  shortened  substring.  This makes a difference to the matching
227           process if the pattern begins with a lookbehind assertion (including \b
228           or \B).
229    
230           If  any  call  to  pcre_exec()  in a /g or /G sequence matches an empty
231           string, the next  call  is  done  with  the  PCRE_NOTEMPTY_ATSTART  and
232           PCRE_ANCHORED  flags  set  in  order  to search for another, non-empty,
233           match at the same point. If this second match fails, the  start  offset
234           is  advanced,  and  the  normal match is retried. This imitates the way
235           Perl handles such cases when using the /g modifier or the split() func-
236           tion.  Normally,  the start offset is advanced by one character, but if
237           the newline convention recognizes CRLF as a newline,  and  the  current
238           character is CR followed by LF, an advance of two is used.
239    
240       Other modifiers
241    
242           There are yet more modifiers for controlling the way pcretest operates.
243    
244           The  /+ modifier requests that as well as outputting the substring that
245           matched the entire pattern, pcretest  should  in  addition  output  the
246           remainder  of  the  subject  string. This is useful for tests where the
247           subject contains multiple copies of the same substring. If the +  modi-
248           fier  appears  twice, the same action is taken for captured substrings.
249           In each case the remainder is output on the following line with a  plus
250           character  following  the  capture number. Note that this modifier must
251           not immediately follow the /S modifier because /S+ has another meaning.
252    
253           The /= modifier requests that the  values  of  all  potential  captured
254           parentheses  be  output  after a match by pcre_exec(). By default, only
255           those up to the highest one actually used in the match are output (cor-
256           responding  to the return code from pcre_exec()). Values in the offsets
257           vector corresponding to higher numbers should be set to -1,  and  these
258           are  output  as  "<unset>".  This modifier gives a way of checking that
259           this is happening.
260    
261           The /B modifier is a debugging feature. It requests that pcretest  out-
262           put  a representation of the compiled byte code after compilation. Nor-
263           mally this information contains length and offset values;  however,  if
264           /Z  is also present, this data is replaced by spaces. This is a special
265           feature for use in the automatic test scripts; it ensures that the same
266           output is generated for different internal link sizes.
267    
268           The  /D modifier is a PCRE debugging feature, and is equivalent to /BI,
269           that is, both the /B and the /I modifiers.
270    
271           The /F modifier causes pcretest to flip the byte order of the fields in
272           the  compiled  pattern  that  contain  2-byte  and 4-byte numbers. This
273           facility is for testing the feature in PCRE that allows it  to  execute
274           patterns that were compiled on a host with a different endianness. This
275           feature is not available when the POSIX  interface  to  PCRE  is  being
276           used,  that is, when the /P pattern modifier is specified. See also the
277           section about saving and reloading compiled patterns below.
278    
279           The /I modifier requests that pcretest  output  information  about  the
280           compiled  pattern (whether it is anchored, has a fixed first character,
281           and so on). It does this by calling pcre_fullinfo() after  compiling  a
282           pattern.  If  the pattern is studied, the results of that are also out-
283           put.
284    
285           The /K modifier requests pcretest to show names from backtracking  con-
286           trol  verbs  that  are  returned  from  calls to pcre_exec(). It causes
287           pcretest to create a pcre_extra block if one has not already been  cre-
288           ated by a call to pcre_study(), and to set the PCRE_EXTRA_MARK flag and
289           the mark field within it, every time that pcre_exec() is called. If the
290           variable  that  the  mark field points to is non-NULL for a match, non-
291           match, or partial match, pcretest prints the string to which it points.
292           For a match, this is shown on a line by itself, tagged with "MK:".  For
293           a non-match it is added to the message.
294    
295           The /L modifier must be followed directly by the name of a locale,  for
296           example,
297    
298             /pattern/Lfr_FR
299    
300           For this reason, it must be the last modifier. The given locale is set,
301           pcre_maketables() is called to build a set of character tables for  the
302           locale,  and  this  is then passed to pcre_compile() when compiling the
303           regular expression. Without an /L (or /T) modifier, NULL is  passed  as
304           the tables pointer; that is, /L applies only to the expression on which
305           it appears.
306    
307           The /M modifier causes the size of memory block used to hold  the  com-
308           piled pattern to be output.
309    
310           If  the  /S  modifier appears once, it causes pcre_study() to be called
311           after the expression has been compiled, and the results used  when  the
312           expression  is  matched.  If  /S appears twice, it suppresses studying,
313           even if it was requested externally by the -s command line option. This
314           makes  it possible to specify that certain patterns are always studied,
315           and others are never studied, independently of -s. This feature is used
316           in the test files in a few cases where the output is different when the
317           pattern is studied.
318    
319           If the /S modifier is immediately followed by a + character,  the  call
320           to   pcre_study()  is  made  with  the  PCRE_STUDY_JIT_COMPILE  option,
321           requesting just-in-time optimization support if it is  available.  Note
322           that  there  is  also  a  /+ modifier; it must not be given immediately
323           after /S because this will be misinterpreted. If JIT studying  is  suc-
324           cessful,  it will automatically be used when pcre_exec() is run, except
325           when incompatible run-time options are  specified.  These  include  the
326           partial matching options; a complete list is given in the pcrejit docu-
327           mentation. See also the \J escape sequence below for a way  of  setting
328           the size of the JIT stack.
329    
330           The  /T  modifier  must be followed by a single digit. It causes a spe-
331           cific set of built-in character tables to be passed to  pcre_compile().
332           It is used in the standard PCRE tests to check behaviour with different
333           character tables. The digit specifies the tables as follows:
334    
335             0   the default ASCII tables, as distributed in
336                   pcre_chartables.c.dist
337             1   a set of tables defining ISO 8859 characters
338    
339           In table 1, some characters whose codes are greater than 128 are  iden-
340           tified as letters, digits, spaces, etc.
341    
342       Using the POSIX wrapper API
343    
344           The  /P modifier causes pcretest to call PCRE via the POSIX wrapper API
345           rather than its native API. When /P is set, the following modifiers set
346           options for the regcomp() function:
347    
348             /i    REG_ICASE
349             /m    REG_NEWLINE
350             /N    REG_NOSUB
351             /s    REG_DOTALL     )
352             /U    REG_UNGREEDY   ) These options are not part of
353             /W    REG_UCP        )   the POSIX standard
354             /8    REG_UTF8       )
355    
356           The  /+  modifier  works  as  described  above. All other modifiers are
357           ignored.
358    
359    
360    DATA LINES
361    
362           Before each data line is passed to pcre_exec(),  leading  and  trailing
363           white  space  is removed, and it is then scanned for \ escapes. Some of
364           these are pretty esoteric features, intended for checking out  some  of
365           the  more  complicated features of PCRE. If you are just testing "ordi-
366           nary" regular expressions, you probably don't need any  of  these.  The
367           following escapes are recognized:
368    
369             \a         alarm (BEL, \x07)
370             \b         backspace (\x08)
371             \e         escape (\x27)
372             \f         form feed (\x0c)
373             \n         newline (\x0a)
374             \qdd       set the PCRE_MATCH_LIMIT limit to dd
375                          (any number of digits)
376             \r         carriage return (\x0d)
377             \t         tab (\x09)
378             \v         vertical tab (\x0b)
379             \nnn       octal character (up to 3 octal digits)
380                          always a byte unless > 255 in UTF-8 mode
381             \xhh       hexadecimal byte (up to 2 hex digits)
382             \x{hh...}  hexadecimal character, any number of digits
383                          in UTF-8 mode
384             \A         pass the PCRE_ANCHORED option to pcre_exec()
385                          or pcre_dfa_exec()
386             \B         pass the PCRE_NOTBOL option to pcre_exec()
387                          or pcre_dfa_exec()
388             \Cdd       call pcre_copy_substring() for substring dd
389                          after a successful match (number less than 32)
390             \Cname     call pcre_copy_named_substring() for substring
391                          "name" after a successful match (name termin-
392                          ated by next non alphanumeric character)
393             \C+        show the current captured substrings at callout
394                          time
395             \C-        do not supply a callout function
396             \C!n       return 1 instead of 0 when callout number n is
397                          reached
398             \C!n!m     return 1 instead of 0 when callout number n is
399                          reached for the nth time
400             \C*n       pass the number n (may be negative) as callout
401                          data; this is used as the callout return value
402             \D         use the pcre_dfa_exec() match function
403             \F         only shortest match for pcre_dfa_exec()
404             \Gdd       call pcre_get_substring() for substring dd
405                          after a successful match (number less than 32)
406             \Gname     call pcre_get_named_substring() for substring
407                          "name" after a successful match (name termin-
408                          ated by next non-alphanumeric character)
409             \Jdd       set up a JIT stack of dd kilobytes maximum (any
410                          number of digits)
411             \L         call pcre_get_substringlist() after a
412                          successful match
413             \M         discover the minimum MATCH_LIMIT and
414                          MATCH_LIMIT_RECURSION settings
415             \N         pass the PCRE_NOTEMPTY option to pcre_exec()
416                          or pcre_dfa_exec(); if used twice, pass the
417                          PCRE_NOTEMPTY_ATSTART option
418             \Odd       set the size of the output vector passed to
419                          pcre_exec() to dd (any number of digits)
420             \P         pass the PCRE_PARTIAL_SOFT option to pcre_exec()
421                          or pcre_dfa_exec(); if used twice, pass the
422                          PCRE_PARTIAL_HARD option
423             \Qdd       set the PCRE_MATCH_LIMIT_RECURSION limit to dd
424                          (any number of digits)
425             \R         pass the PCRE_DFA_RESTART option to pcre_dfa_exec()
426             \S         output details of memory get/free calls during matching
427             \Y         pass the PCRE_NO_START_OPTIMIZE option to pcre_exec()
428                          or pcre_dfa_exec()
429             \Z         pass the PCRE_NOTEOL option to pcre_exec()
430                          or pcre_dfa_exec()
431             \?         pass the PCRE_NO_UTF8_CHECK option to
432                          pcre_exec() or pcre_dfa_exec()
433             \>dd       start the match at offset dd (optional "-"; then
434                          any number of digits); this sets the startoffset
435                          argument for pcre_exec() or pcre_dfa_exec()
436             \<cr>      pass the PCRE_NEWLINE_CR option to pcre_exec()
437                          or pcre_dfa_exec()
438             \<lf>      pass the PCRE_NEWLINE_LF option to pcre_exec()
439                          or pcre_dfa_exec()
440             \<crlf>    pass the PCRE_NEWLINE_CRLF option to pcre_exec()
441                          or pcre_dfa_exec()
442             \<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to pcre_exec()
443                          or pcre_dfa_exec()
444             \<any>     pass the PCRE_NEWLINE_ANY option to pcre_exec()
445                          or pcre_dfa_exec()
446    
447           Note  that  \xhh  always  specifies  one byte, even in UTF-8 mode; this
448           makes it possible to construct invalid UTF-8 sequences for testing pur-
449           poses. On the other hand, \x{hh} is interpreted as a UTF-8 character in
450           UTF-8 mode, generating more than one byte if the value is greater  than
451           127. When not in UTF-8 mode, it generates one byte for values less than
452           256, and causes an error for greater values.
453    
454           The escapes that specify line ending  sequences  are  literal  strings,
455           exactly as shown. No more than one newline setting should be present in
456           any data line.
457    
458           A backslash followed by anything else just escapes the  anything  else.
459           If  the very last character is a backslash, it is ignored. This gives a
460           way of passing an empty line as data, since a real  empty  line  termi-
461           nates the data input.
462    
463           The  \J escape provides a way of setting the maximum stack size that is
464           used by the just-in-time optimization code. It is ignored if JIT  opti-
465           mization  is  not being used. Providing a stack that is larger than the
466           default 32K is necessary only for very complicated patterns.
467    
468           If \M is present, pcretest calls pcre_exec() several times,  with  dif-
469           ferent  values  in  the match_limit and match_limit_recursion fields of
470           the pcre_extra data structure, until it finds the minimum  numbers  for
471           each  parameter  that  allow  pcre_exec()  to  complete  without error.
472           Because this is testing a specific feature of the  normal  interpretive
473           pcre_exec()  execution, the use of any JIT optimization that might have
474           been set up by the /S+ qualifier of -s+ option is disabled.
475    
476           The match_limit number is a measure of the amount of backtracking  that
477           takes  place,  and  checking it out can be instructive. For most simple
478           matches, the number is quite small, but for patterns  with  very  large
479           numbers  of  matching  possibilities,  it can become large very quickly
480           with increasing length of  subject  string.  The  match_limit_recursion
481           number  is  a  measure  of how much stack (or, if PCRE is compiled with
482           NO_RECURSE, how much heap) memory  is  needed  to  complete  the  match
483           attempt.
484    
485           When  \O  is  used, the value specified may be higher or lower than the
486           size set by the -O command line option (or defaulted to 45); \O applies
487           only to the call of pcre_exec() for the line in which it appears.
488    
489           If  the /P modifier was present on the pattern, causing the POSIX wrap-
490           per API to be used, the only option-setting  sequences  that  have  any
491           effect  are  \B,  \N,  and  \Z,  causing  REG_NOTBOL, REG_NOTEMPTY, and
492           REG_NOTEOL, respectively, to be passed to regexec().
493    
494           The use of \x{hh...} to represent UTF-8 characters is not dependent  on
495           the  use  of  the  /8 modifier on the pattern. It is recognized always.
496           There may be any number of hexadecimal digits inside  the  braces.  The
497           result  is  from  one  to  six bytes, encoded according to the original
498           UTF-8 rules of RFC 2279. This allows for  values  in  the  range  0  to
499           0x7FFFFFFF.  Note  that not all of those are valid Unicode code points,
500           or indeed valid UTF-8 characters according to the later  rules  in  RFC
501           3629.
502    
503    
504    THE ALTERNATIVE MATCHING FUNCTION
505    
506           By   default,  pcretest  uses  the  standard  PCRE  matching  function,
507           pcre_exec() to match each data line. From release 6.0, PCRE supports an
508           alternative  matching  function,  pcre_dfa_test(),  which operates in a
509           different way, and has some restrictions. The differences  between  the
510           two functions are described in the pcrematching documentation.
511    
512           If  a data line contains the \D escape sequence, or if the command line
513           contains the -dfa option, the alternative matching function is  called.
514           This function finds all possible matches at a given point. If, however,
515           the \F escape sequence is present in the data line, it stops after  the
516           first match is found. This is always the shortest possible match.
517    
518    
519    DEFAULT OUTPUT FROM PCRETEST
520    
521           This  section  describes  the output when the normal matching function,
522           pcre_exec(), is being used.
523    
524           When a match succeeds, pcretest outputs the list of captured substrings
525           that  pcre_exec()  returns,  starting with number 0 for the string that
526           matched the whole pattern. Otherwise, it outputs "No  match"  when  the
527           return is PCRE_ERROR_NOMATCH, and "Partial match:" followed by the par-
528           tially matching substring when pcre_exec() returns  PCRE_ERROR_PARTIAL.
529           (Note  that  this is the entire substring that was inspected during the
530           partial match; it may include characters before the actual match  start
531           if  a  lookbehind assertion, \K, \b, or \B was involved.) For any other
532           return, pcretest outputs the PCRE negative error  number  and  a  short
533           descriptive  phrase.  If  the error is a failed UTF-8 string check, the
534           byte offset of the start of the failing character and the  reason  code
535           are  also  output,  provided  that  the size of the output vector is at
536           least two. Here is an example of an interactive pcretest run.
537    
538             $ pcretest
539             PCRE version 8.13 2011-04-30
540    
541               re> /^abc(\d+)/
542             data> abc123
543              0: abc123
544              1: 123
545             data> xyz
546             No match
547    
548           Unset capturing substrings that are not followed by one that is set are
549           not returned by pcre_exec(), and are not shown by pcretest. In the fol-
550           lowing example, there are two capturing substrings, but when the  first
551           data  line  is  matched,  the  second, unset substring is not shown. An
552           "internal" unset substring is shown as "<unset>",  as  for  the  second
553           data line.
554    
555               re> /(a)|(b)/
556             data> a
557              0: a
558              1: a
559             data> b
560              0: b
561              1: <unset>
562              2: b
563    
564           If  the strings contain any non-printing characters, they are output as
565           \0x escapes, or as \x{...} escapes if the /8 modifier  was  present  on
566           the  pattern.  See below for the definition of non-printing characters.
567           If the pattern has the /+ modifier, the output for substring 0 is  fol-
568           lowed  by  the  the rest of the subject string, identified by "0+" like
569           this:
570    
571               re> /cat/+
572             data> cataract
573              0: cat
574              0+ aract
575    
576           If the pattern has the /g or /G modifier,  the  results  of  successive
577           matching attempts are output in sequence, like this:
578    
579               re> /\Bi(\w\w)/g
580             data> Mississippi
581              0: iss
582              1: ss
583              0: iss
584              1: ss
585              0: ipp
586              1: pp
587    
588           "No  match" is output only if the first match attempt fails. Here is an
589           example of a failure message (the offset 4 that is specified by \>4  is
590           past the end of the subject string):
591    
592               re> /xyz/
593             data> xyz\>4
594             Error -24 (bad offset value)
595    
596           If  any  of the sequences \C, \G, or \L are present in a data line that
597           is successfully matched, the substrings extracted  by  the  convenience
598           functions are output with C, G, or L after the string number instead of
599           a colon. This is in addition to the normal full list. The string length
600           (that  is,  the return from the extraction function) is given in paren-
601           theses after each string for \C and \G.
602    
603           Note that whereas patterns can be continued over several lines (a plain
604           ">" prompt is used for continuations), data lines may not. However new-
605           lines can be included in data by means of the \n escape (or  \r,  \r\n,
606           etc., depending on the newline sequence setting).
607    
608    
609    OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION
610    
611           When  the  alternative  matching function, pcre_dfa_exec(), is used (by
612           means of the \D escape sequence or the -dfa command line  option),  the
613           output  consists  of  a list of all the matches that start at the first
614           point in the subject where there is at least one match. For example:
615    
616               re> /(tang|tangerine|tan)/
617             data> yellow tangerine\D
618              0: tangerine
619              1: tang
620              2: tan
621    
622           (Using the normal matching function on this data  finds  only  "tang".)
623           The  longest matching string is always given first (and numbered zero).
624           After a PCRE_ERROR_PARTIAL return, the output is "Partial match:", fol-
625           lowed  by  the  partially  matching  substring.  (Note that this is the
626           entire substring that was inspected during the partial  match;  it  may
627           include characters before the actual match start if a lookbehind asser-
628           tion, \K, \b, or \B was involved.)
629    
630           If /g is present on the pattern, the search for further matches resumes
631           at the end of the longest match. For example:
632    
633               re> /(tang|tangerine|tan)/g
634             data> yellow tangerine and tangy sultana\D
635              0: tangerine
636              1: tang
637              2: tan
638              0: tang
639              1: tan
640              0: tan
641    
642           Since  the  matching  function  does not support substring capture, the
643           escape sequences that are concerned with captured  substrings  are  not
644           relevant.
645    
646    
647    RESTARTING AFTER A PARTIAL MATCH
648    
649           When the alternative matching function has given the PCRE_ERROR_PARTIAL
650           return, indicating that the subject partially matched the pattern,  you
651           can  restart  the match with additional subject data by means of the \R
652           escape sequence. For example:
653    
654               re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/
655             data> 23ja\P\D
656             Partial match: 23ja
657             data> n05\R\D
658              0: n05
659    
660           For further information about partial  matching,  see  the  pcrepartial
661           documentation.
662    
663    
664    CALLOUTS
665    
666           If  the pattern contains any callout requests, pcretest's callout func-
667           tion is called during matching. This works  with  both  matching  func-
668           tions. By default, the called function displays the callout number, the
669           start and current positions in the text at the callout  time,  and  the
670           next pattern item to be tested. For example, the output
671    
672             --->pqrabcdef
673               0    ^  ^     \d
674    
675           indicates  that  callout number 0 occurred for a match attempt starting
676           at the fourth character of the subject string, when the pointer was  at
677           the  seventh  character of the data, and when the next pattern item was
678           \d. Just one circumflex is output if the start  and  current  positions
679           are the same.
680    
681           Callouts numbered 255 are assumed to be automatic callouts, inserted as
682           a result of the /C pattern modifier. In this case, instead  of  showing
683           the  callout  number, the offset in the pattern, preceded by a plus, is
684           output. For example:
685    
686               re> /\d?[A-E]\*/C
687             data> E*
688             --->E*
689              +0 ^      \d?
690              +3 ^      [A-E]
691              +8 ^^     \*
692             +10 ^ ^
693              0: E*
694    
695           If a pattern contains (*MARK) items, an additional line is output when-
696           ever  a  change  of  latest mark is passed to the callout function. For
697           example:
698    
699               re> /a(*MARK:X)bc/C
700             data> abc
701             --->abc
702              +0 ^       a
703              +1 ^^      (*MARK:X)
704             +10 ^^      b
705             Latest Mark: X
706             +11 ^ ^     c
707             +12 ^  ^
708              0: abc
709    
710           The mark changes between matching "a" and "b", but stays the  same  for
711           the  rest  of  the match, so nothing more is output. If, as a result of
712           backtracking, the mark reverts to being unset, the  text  "<unset>"  is
713           output.
714    
715           The  callout  function  in pcretest returns zero (carry on matching) by
716           default, but you can use a \C item in a data line (as described  above)
717           to change this and other parameters of the callout.
718    
719           Inserting  callouts can be helpful when using pcretest to check compli-
720           cated regular expressions. For further information about callouts,  see
721           the pcrecallout documentation.
722    
723    
724    NON-PRINTING CHARACTERS
725    
726           When  pcretest is outputting text in the compiled version of a pattern,
727           bytes other than 32-126 are always treated as  non-printing  characters
728           are are therefore shown as hex escapes.
729    
730           When  pcretest  is  outputting text that is a matched part of a subject
731           string, it behaves in the same way, unless a different locale has  been
732           set  for  the  pattern  (using  the  /L  modifier).  In  this case, the
733           isprint() function to distinguish printing and non-printing characters.
734    
735    
736    SAVING AND RELOADING COMPILED PATTERNS
737    
738           The facilities described in this section are  not  available  when  the
739           POSIX  interface  to  PCRE  is being used, that is, when the /P pattern
740           modifier is specified.
741    
742           When the POSIX interface is not in use, you can cause pcretest to write
743           a  compiled  pattern to a file, by following the modifiers with > and a
744           file name.  For example:
745    
746             /pattern/im >/some/file
747    
748           See the pcreprecompile documentation for a discussion about saving  and
749           re-using  compiled patterns.  Note that if the pattern was successfully
750           studied with JIT optimization, the JIT data cannot be saved.
751    
752           The data that is written is binary.  The  first  eight  bytes  are  the
753           length  of  the  compiled  pattern  data  followed by the length of the
754           optional study data, each written as four  bytes  in  big-endian  order
755           (most  significant  byte  first). If there is no study data (either the
756           pattern was not studied, or studying did not return any data), the sec-
757           ond  length  is  zero. The lengths are followed by an exact copy of the
758           compiled pattern. If there is additional study  data,  this  (excluding
759           any  JIT  data)  follows  immediately after the compiled pattern. After
760           writing the file, pcretest expects to read a new pattern.
761    
762           A saved pattern can be reloaded into pcretest by  specifying  <  and  a
763           file name instead of a pattern. The name of the file must not contain a
764           < character, as otherwise pcretest will interpret the line as a pattern
765           delimited by < characters.  For example:
766    
767              re> </some/file
768             Compiled pattern loaded from /some/file
769             No study data
770    
771           If  the  pattern  was previously studied with the JIT optimization, the
772           JIT information cannot be saved and restored, and so is lost. When  the
773           pattern  has  been  loaded, pcretest proceeds to read data lines in the
774           usual way.
775    
776           You can copy a file written by pcretest to a different host and  reload
777           it  there,  even  if the new host has opposite endianness to the one on
778           which the pattern was compiled. For example, you can compile on an  i86
779           machine and run on a SPARC machine.
780    
781           File  names  for  saving and reloading can be absolute or relative, but
782           note that the shell facility of expanding a file name that starts  with
783           a tilde (~) is not available.
784    
785           The  ability to save and reload files in pcretest is intended for test-
786           ing and experimentation. It is not intended for production use  because
787           only  a  single pattern can be written to a file. Furthermore, there is
788           no facility for supplying  custom  character  tables  for  use  with  a
789           reloaded  pattern.  If  the  original  pattern was compiled with custom
790           tables, an attempt to match a subject string using a  reloaded  pattern
791           is  likely to cause pcretest to crash.  Finally, if you attempt to load
792           a file that is not in the correct format, the result is undefined.
793    
794    
795    SEE ALSO
796    
797           pcre(3), pcreapi(3), pcrecallout(3), pcrejit, pcrematching(3), pcrepar-
798           tial(d), pcrepattern(3), pcreprecompile(3).
799    
800    
801    AUTHOR
802    
803           Philip Hazel
804           University Computing Service
805           Cambridge CB2 3QH, England.
806    
807    
808    REVISION
809    
810           Last updated: 26 August 2011
811           Copyright (c) 1997-2011 University of Cambridge.

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