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pcretest

PCRETEST(1)                                                        PCRETEST(1)



NAME
       pcretest - a program for testing Perl-compatible regular expressions.

SYNOPSIS
       pcretest [-d] [-i] [-m] [-o osize] [-p] [-t] [source] [destination]

       pcretest  was written as a test program for the PCRE regular expression
       library itself, but it can also be used for experimenting with  regular
       expressions.  This man page describes the features of the test program;
       for details of the regular expressions themselves,  see  the  pcre  man
       page.


OPTIONS
       -d        Behave  as if each regex had the /D modifier (see below); the
                 internal form is output after compilation.

       -i        Behave as if each regex  had  the  /I  modifier;  information
                 about the compiled pattern is given after compilation.

       -m        Output  the  size  of each compiled pattern after it has been
                 compiled. This is equivalent to adding  /M  to  each  regular
                 expression.   For  compatibility  with  earlier  versions  of
                 pcretest, -s is a synonym for -m.

       -o osize  Set the number of elements in the output vector that is  used
                 when calling PCRE to be osize. The default value is 45, which
                 is enough for 14 capturing subexpressions.  The  vector  size
                 can  be changed for individual matching calls by including \O
                 in the data line (see below).

       -p        Behave as if each regex has /P modifier;  the  POSIX  wrapper
                 API  is  used to call PCRE. None of the other options has any
                 effect when -p is set.

       -t        Run each compile, study, and match 20000 times with a  timer,
                 and  output resulting time per compile or match (in millisec-
                 onds). Do not set -t with -m, because you will then  get  the
                 size output 20000 times and the timing will be distorted.



DESCRIPTION
       If  pcretest  is  given two filename arguments, it reads from the first
       and writes to the second. If it is given only one filename argument, it
       reads  from  that  file  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 num-
       ber of data lines to be matched against the pattern. An empty line sig-
       nals 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 expres-
       sion may be continued over several input lines, in which case the  new-
       line  characters  are included within it. 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  fol-
       lowed 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.



PATTERN MODIFIERS
       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 differ-
       ence between /g and /G is that the former uses the startoffset argument
       to pcre_exec() to start searching at a  new  point  within  the  entire
       string  (which  is in effect what Perl does), whereas the latter passes
       over a shortened substring. This makes a  difference  to  the  matching
       process if the pattern begins with a lookbehind assertion (including \b
       or \B).

       If any call to pcre_exec() in a /g or  /G  sequence  matches  an  empty
       string,  the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
       flags set in order to search for another, non-empty, match at the  same
       point.   If  this  second  match fails, the start offset is advanced by
       one, and the normal match is retried. This imitates the way  Perl  han-
       dles 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  compil-
       ing  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  charac-
       ter,  and so on). It does this by calling pcre_fullinfo() after compil-
       ing 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 com-
       piled pattern to be output.

       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.

       The  /8 modifier causes pcretest to call PCRE with the PCRE_UTF8 option
       set. This turns on the (currently incomplete) support for UTF-8 charac-
       ter  handling  in PCRE, provided that it was compiled with this support
       enabled. This modifier also causes any non-printing characters in  out-
       put  strings  to  be  printed  using the \x{hh...} notation if they are
       valid UTF-8 sequences.



DATA LINES
       Before each data line is passed to pcre_exec(),  leading  and  trailing
       whitespace  is  removed, and it is then scanned for \ escapes. The fol-
       lowing 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)
         \x{hh...}  hexadecimal UTF-8 character

         \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()

       When \O is used, it may be higher or lower than the size set by the  -O
       option (or defaulted to 45); \O applies only to the call of pcre_exec()
       for the line in which it appears.

       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  termi-
       nates the data input.

       If  /P  was  present  on the regex, causing the POSIX wrapper API to be
       used, only  0  causing  REG_NOTBOL  and  REG_NOTEOL  to  be  passed  to
       regexec() respectively.

       The  use of \x{hh...} to represent UTF-8 characters is not dependent on
       the use of the /8 modifier on the pattern.  It  is  recognized  always.
       There  may  be  any number of hexadecimal digits inside the braces. The
       result is from one to six bytes, encoded according to the UTF-8  rules.



OUTPUT FROM PCRETEST
       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,  or  as \x{...} escapes if the /8 modifier was present on
       the pattern. If the pattern has the /+ modifier, then  the  output  for
       substring  0 is followed by the the rest of the subject string, identi-
       fied 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 the sequences \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 paren-
       theses 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 new-
       lines can be included in data by means of the \n escape.



AUTHOR
       Philip Hazel <ph10@cam.ac.uk>
       University Computing Service,
       New Museums Site,
       Cambridge CB2 3QG, England.
       Phone: +44 1223 334714

       Last updated: 15 August 2001
       Copyright (c) 1997-2001 University of Cambridge.



                                                                   PCRETEST(1)