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 which 
is built with Exim.
-------------------------------------------------------------------------------

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


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

     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   available  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 compila-
               tion.

     -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  cap-
               turing  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 milliseconds). 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  number  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 single line of input to encode the new-
     line  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 expres-
     sions 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 regu-
     lar expression may be continued over several input lines, in
     which case the newline 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 followed by a backslash, for exam-
     ple,

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

     If any call to pcre_exec() in a /g or /G sequence matches an
     empty  string,  the next call is done with the PCRE_NOTEMPTY
     and PCRE_ANCHORED flags set in order to search for  another,
     non-empty,  match  at  the same point.  If this second match
     fails, the start offset is advanced by one, and  the  normal
     match  is  retried.  This imitates the way Perl handles such
     cases when using the /g modifier or the split() function.

     There are a number of other modifiers  for  controlling  the
     way pcretest operates.

     The /+ modifier requests that as well as outputting the sub-
     string  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 expres-
     sion. 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 output-
     ting the information it gets back. If the  pattern  is  stu-
     died, 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 compiled 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 char-
     acter handling in PCRE, provided 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 function 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  func-
     tion returns zero (carry on matching) by default.

     Inserting callouts may be helpful  when  using  pcretest  to
     check  complicated regular expressions. For further informa-
     tion 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 following 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 "ordinary" regular
     expressions,  you probably don't need any of these. The fol-
     lowing 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)
       \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  different  values  in  the  match_limit  field  of the
     pcre_extra data structure, 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 pat-
     terns  with very large numbers of matching possibilities, it
     can become large very quickly with increasing length of sub-
     ject 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  any-
     thing 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()  respec-
     tively.
     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, 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 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 addi-
     tion 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.


AUTHOR

     Philip Hazel <ph10@cam.ac.uk>
     University Computing Service,
     Cambridge CB2 3QG, England.

Last updated: 20 August 2003
Copyright (c) 1997-2003 University of Cambridge.
