This file contains the PCRE man page that described the pcretest program. Note 
that not all of the features of PCRE are available in the limited version that 
is built with Exim.
-------------------------------------------------------------------------------

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 document describes the features of the test program;
       for details of the regular expressions themselves, see the  pcrepattern
       documentation.  For  details  of  PCRE and its options, see the pcreapi
       documentation.


OPTIONS


       -C        Output the version number of the PCRE library, and all avail-
                 able   information  about  the  optional  features  that  are
                 included, and then exit.

       -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 many 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.

       Each  line  is  matched separately and independently. If you want to do
       multiple-line matches, you have to use the \n escape sequence in a sin-
       gle  line of input to encode the newline characters. The maximum length
       of data line is 30,000 characters.

       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  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 that set PCRE options that do not correspond to anything in
       Perl: /A, /E, /N, /U, and /X  set  PCRE_ANCHORED,  PCRE_DOLLAR_ENDONLY,
       PCRE_NO_AUTO_CAPTURE, PCRE_UNGREEDY, 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. If the pattern was studied, the information returned
       is also output.

       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 support for UTF-8 character handling in  PCRE,  pro-
       vided  that  it  was  compiled with this support enabled. This modifier
       also causes any non-printing characters in output strings to be printed
       using the \x{hh...} notation if they are valid UTF-8 sequences.

       If  the  /?  modifier  is  used  with  /8,  it  causes pcretest to call
       pcre_compile() with the  PCRE_NO_UTF8_CHECK  option,  to  suppress  the
       checking of the string for UTF-8 validity.


CALLOUTS

       If  the pattern contains any callout requests, pcretest's callout func-
       tion will be called. By default, it displays the  callout  number,  and
       the  start  and  current positions in the text at the callout time. For
       example, the output

         --->pqrabcdef
           0    ^  ^

       indicates that callout number 0 occurred for a match  attempt  starting
       at  the fourth character of the subject string, when the pointer was at
       the seventh character. The callout  function  returns  zero  (carry  on
       matching) by default.

       Inserting  callouts may be helpful when using pcretest to check compli-
       cated regular expressions. For further information about callouts,  see
       the pcrecallout documentation.

       For  testing  the PCRE library, additional control of callout behaviour
       is available via escape sequences in the data, as described in the fol-
       lowing  section.  In  particular, it is possible to pass in a number as
       callout data (the default is zero). If the callout function receives  a
       non-zero number, it returns that value instead of zero.


DATA LINES

       Before  each  data  line is passed to pcre_exec(), leading and trailing
       whitespace is removed, and it is then scanned for \  escapes.  Some  of
       these  are  pretty esoteric features, intended for checking out some of
       the more complicated features of PCRE. If you are just  testing  "ordi-
       nary"  regular  expressions,  you probably don't need any of these. The
       following escapes 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 character, any number of digits
                      in UTF-8 mode
         \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)
         \Cname     call pcre_copy_named_substring() for substring
                      "name" after a successful match (name termin-
                      ated by next non alphanumeric character)
         \C+        show the current captured substrings at callout
                      time
         \C-        do not supply a callout function
         \C!n       return 1 instead of 0 when callout number n is
                      reached
         \C!n!m     return 1 instead of 0 when callout number n is
                      reached for the nth time
         \C*n       pass the number n (may be negative) as callout
                      data
         \Gdd       call pcre_get_substring() for substring dd
                      after a successful match (any decimal number
                      less than 32)
         \Gname     call pcre_get_named_substring() for substring
                      "name" after a successful match (name termin-
                      ated by next non-alphanumeric character)
         \L         call pcre_get_substringlist() after a
                      successful match
         \M         discover the minimum MATCH_LIMIT setting
         \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)
         \S         output details of memory get/free calls during matching
         \Z         pass the PCRE_NOTEOL option to pcre_exec()
         \?         pass the PCRE_NO_UTF8_CHECK option to
                      pcre_exec()

       If \M is present, pcretest calls pcre_exec() several times,  with  dif-
       ferent  values  in  the match_limit field of the pcre_extra data struc-
       ture, until it finds the minimum number that is needed for  pcre_exec()
       to  complete.  This  number is a measure of the amount of recursion and
       backtracking that takes place, and checking it out can be  instructive.
       For  most  simple  matches, the number is quite small, but for patterns
       with very large numbers of matching possibilities, it can become  large
       very quickly with increasing length of subject string.

       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 4.00 08-Jan-2003

           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,
       Cambridge CB2 3QG, England.

Last updated: 09 December 2003
Copyright (c) 1997-2003 University of Cambridge.
