PCRETEST(1)                                                        PCRETEST(1)


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


SYNOPSIS

       pcretest [options] [input file [output file]]

       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 the PCRE library function calls and their
       options, see the pcreapi documentation. The input  for  pcretest  is  a
       sequence  of  regular expression patterns and strings to be matched, as
       described below. The output shows the result of each match. Options  on
       the command line and the patterns control PCRE options and exactly what
       is output.


COMMAND LINE OPTIONS

       -b        Behave as if each pattern has the /B (show byte  code)  modi-
                 fier; the internal form is output after compilation.

       -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 pattern has the /D (debug) modifier; the
                 internal form and information about the compiled  pattern  is
                 output after compilation; -d is equivalent to -b -i.

       -dfa      Behave  as if each data line contains the \D escape sequence;
                 this    causes    the    alternative    matching    function,
                 pcre_dfa_exec(),   to   be   used  instead  of  the  standard
                 pcre_exec() function (more detail is given below).

       -help     Output a brief summary these options and then exit.

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

       -M        Behave  as if each data line contains the \M escape sequence;
                 this causes PCRE to  discover  the  minimum  MATCH_LIMIT  and
                 MATCH_LIMIT_RECURSION settings by calling pcre_exec() repeat-
                 edly with different limits.

       -m        Output the size of each compiled pattern after  it  has  been
                 compiled.  This  is  equivalent  to adding /M to each regular
                 expression.

       -o osize  Set the number of elements in the output vector that is  used
                 when  calling pcre_exec() or pcre_dfa_exec() to be osize. The
                 default value is 45, which is enough for 14 capturing  subex-
                 pressions   for  pcre_exec()  or  22  different  matches  for
                 pcre_dfa_exec(). The vector size can be changed for  individ-
                 ual  matching  calls  by  including  \O in the data line (see
                 below).

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

       -q        Do not output the version number of pcretest at the start  of
                 execution.

       -S size   On  Unix-like  systems, set the size of the run-time stack to
                 size megabytes.

       -s        Behave as if each pattern  has  the  /S  modifier;  in  other
                 words,  force  each  pattern  to  be studied. If the /I or /D
                 option is present on a pattern (requesting output  about  the
                 compiled  pattern),  information about the result of studying
                 is not included when studying is caused only by -s  and  nei-
                 ther -i nor -d is present on the command line. This behaviour
                 means that the output from tests that are run with and  with-
                 out  -s  should be identical, except when options that output
                 information about the actual running of a match are set.  The
                 -M,  -t,  and  -tm  options,  which  give  information  about
                 resources used, are likely to produce different  output  with
                 and  without  -s.  Output may also differ if the /C option is
                 present on an individual pattern. This uses callouts to trace
                 the  the  matching process, and this may be different between
                 studied and non-studied patterns.  If  the  pattern  contains
                 (*MARK)  items  there  may  also be differences, for the same
                 reason. The -s command line option can be overridden for spe-
                 cific  patterns  that  should  never  be  studied (see the /S
                 option below).

       -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 -m with -t, because you will then  get  the
                 size  output  a  zillion  times,  and the timing will be dis-
                 torted. You can control the number  of  iterations  that  are
                 used  for timing by following -t with a number (as a separate
                 item on the command line). For example, "-t 1000" would iter-
                 ate 1000 times. The default is to iterate 500000 times.

       -tm       This is like -t except that it times only the matching phase,
                 not the compile or study phases.


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.

       When  pcretest  is  built,  a  configuration option can specify that it
       should be linked with the libreadline library. When this  is  done,  if
       the input is from a terminal, it is read using the readline() function.
       This provides line-editing and history facilities. The output from  the
       -help option states whether or not readline() will be used.

       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  data line is matched separately and independently. If you want to
       do multi-line matches, you have to use the \n escape sequence (or \r or
       \r\n, etc., depending on the newline setting) in a single line of input
       to encode the newline sequences. There is no limit  on  the  length  of
       data  lines;  the  input  buffer is automatically extended if it is too
       small.

       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-alphanumeric 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-alphanumeric, 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

       A pattern may be followed by any number of modifiers, which are  mostly
       single  characters.  Following  Perl usage, these are referred to below
       as, for example, "the /i modifier", even though the  delimiter  of  the
       pattern  need  not always be a slash, and no slash is used when writing
       modifiers. White space may appear between the final  pattern  delimiter
       and the first modifier, and between the modifiers themselves.

       The /i, /m, /s, and /x modifiers set the PCRE_CASELESS, PCRE_MULTILINE,
       PCRE_DOTALL, or PCRE_EXTENDED  options,  respectively,  when  pcre_com-
       pile()  is  called. These four modifier letters have the same effect as
       they do in Perl. For example:

         /caseless/i

       The following table shows additional modifiers for  setting  PCRE  com-
       pile-time options that do not correspond to anything in Perl:

         /8              PCRE_UTF8
         /?              PCRE_NO_UTF8_CHECK
         /A              PCRE_ANCHORED
         /C              PCRE_AUTO_CALLOUT
         /E              PCRE_DOLLAR_ENDONLY
         /f              PCRE_FIRSTLINE
         /J              PCRE_DUPNAMES
         /N              PCRE_NO_AUTO_CAPTURE
         /U              PCRE_UNGREEDY
         /W              PCRE_UCP
         /X              PCRE_EXTRA
         /Y              PCRE_NO_START_OPTIMIZE
         /<JS>           PCRE_JAVASCRIPT_COMPAT
         /<cr>           PCRE_NEWLINE_CR
         /<lf>           PCRE_NEWLINE_LF
         /<crlf>         PCRE_NEWLINE_CRLF
         /<anycrlf>      PCRE_NEWLINE_ANYCRLF
         /<any>          PCRE_NEWLINE_ANY
         /<bsr_anycrlf>  PCRE_BSR_ANYCRLF
         /<bsr_unicode>  PCRE_BSR_UNICODE

       The  modifiers  that are enclosed in angle brackets are literal strings
       as shown, including the angle brackets, but the letters within  can  be
       in  either case.  This example sets multiline matching with CRLF as the
       line ending sequence:

         /^abc/m<CRLF>

       As well as turning on the PCRE_UTF8 option, the /8 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. Full  details  of
       the PCRE options are given in the pcreapi documentation.

   Finding all matches in a string

       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_ATSTART  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,  and  the  normal match is retried. This imitates the way
       Perl handles such cases when using the /g modifier or the split() func-
       tion.  Normally,  the start offset is advanced by one character, but if
       the newline convention recognizes CRLF as a newline,  and  the  current
       character is CR followed by LF, an advance of two is used.

   Other modifiers

       There are yet more 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. If the +  modi-
       fier  appears  twice, the same action is taken for captured substrings.
       In each case the remainder is output on the following line with a  plus
       character following the capture number.

       The  /=  modifier  requests  that  the values of all potential captured
       parentheses be output after a match by pcre_exec().  By  default,  only
       those up to the highest one actually used in the match are output (cor-
       responding to the return code from pcre_exec()). Values in the  offsets
       vector  corresponding  to higher numbers should be set to -1, and these
       are output as "<unset>". This modifier gives a  way  of  checking  that
       this is happening.

       The  /B modifier is a debugging feature. It requests that pcretest out-
       put a representation of the compiled byte code after compilation.  Nor-
       mally  this  information contains length and offset values; however, if
       /Z is also present, this data is replaced by spaces. This is a  special
       feature for use in the automatic test scripts; it ensures that the same
       output is generated for different internal link sizes.

       The /D modifier is a PCRE debugging feature, and is equivalent to  /BI,
       that is, both the /B and the /I modifiers.

       The /F modifier causes pcretest to flip the byte order of the fields in
       the compiled pattern that  contain  2-byte  and  4-byte  numbers.  This
       facility  is  for testing the feature in PCRE that allows it to execute
       patterns that were compiled on a host with a different endianness. This
       feature  is  not  available  when  the POSIX interface to PCRE is being
       used, that is, when the /P pattern modifier is specified. See also  the
       section about saving and reloading compiled patterns below.

       The  /I  modifier  requests  that pcretest output information about the
       compiled pattern (whether it is anchored, has a fixed first  character,
       and  so  on). It does this by calling pcre_fullinfo() after compiling a
       pattern. If the pattern is studied, the results of that are  also  out-
       put.

       The  /K modifier requests pcretest to show names from backtracking con-
       trol verbs that are returned  from  calls  to  pcre_exec().  It  causes
       pcretest  to create a pcre_extra block if one has not already been cre-
       ated by a call to pcre_study(), and to set the PCRE_EXTRA_MARK flag and
       the mark field within it, every time that pcre_exec() is called. If the
       variable that the mark field points to is non-NULL for  a  match,  non-
       match, or partial match, pcretest prints the string to which it points.
       For a match, this is shown on a line by itself, tagged with "MK:".  For
       a non-match it is added to the message.

       The  /L modifier must be followed directly by the name of a locale, for
       example,

         /pattern/Lfr_FR

       For this reason, it must be the last modifier. 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 (or /T) modifier, NULL is passed as
       the tables pointer; that is, /L applies only to the expression on which
       it appears.

       The  /M  modifier causes the size of memory block used to hold the com-
       piled pattern to be output.

       If the /S modifier appears once, it causes pcre_study()  to  be  called
       after  the  expression has been compiled, and the results used when the
       expression is matched. If /S appears  twice,  it  suppresses  studying,
       even if it was requested externally by the -s command line option. This
       makes it possible to specify that certain patterns are always  studied,
       and others are never studied, independently of -s. This feature is used
       in the test files in a few cases where the output is different when the
       pattern is studied.

       The  /T  modifier  must be followed by a single digit. It causes a spe-
       cific set of built-in character tables to be passed to  pcre_compile().
       It is used in the standard PCRE tests to check behaviour with different
       character tables. The digit specifies the tables as follows:

         0   the default ASCII tables, as distributed in
               pcre_chartables.c.dist
         1   a set of tables defining ISO 8859 characters

       In table 1, some characters whose codes are greater than 128 are  iden-
       tified as letters, digits, spaces, etc.

   Using the POSIX wrapper API

       The  /P modifier causes pcretest to call PCRE via the POSIX wrapper API
       rather than its native API. When /P is set, the following modifiers set
       options for the regcomp() function:

         /i    REG_ICASE
         /m    REG_NEWLINE
         /N    REG_NOSUB
         /s    REG_DOTALL     )
         /U    REG_UNGREEDY   ) These options are not part of
         /W    REG_UCP        )   the POSIX standard
         /8    REG_UTF8       )

       The  /+  modifier  works  as  described  above. All other modifiers are
       ignored.


DATA LINES

       Before each data line is passed to pcre_exec(),  leading  and  trailing
       white  space  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, \x07)
         \b         backspace (\x08)
         \e         escape (\x27)
         \f         form feed (\x0c)
         \n         newline (\x0a)
         \qdd       set the PCRE_MATCH_LIMIT limit to dd
                      (any number of digits)
         \r         carriage return (\x0d)
         \t         tab (\x09)
         \v         vertical tab (\x0b)
         \nnn       octal character (up to 3 octal digits)
                      always a byte unless > 255 in UTF-8 mode
         \xhh       hexadecimal byte (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()
                      or pcre_dfa_exec()
         \B         pass the PCRE_NOTBOL option to pcre_exec()
                      or pcre_dfa_exec()
         \Cdd       call pcre_copy_substring() for substring dd
                      after a successful match (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; this is used as the callout return value
         \D         use the pcre_dfa_exec() match function
         \F         only shortest match for pcre_dfa_exec()
         \Gdd       call pcre_get_substring() for substring dd
                      after a successful match (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 and
                      MATCH_LIMIT_RECURSION settings
         \N         pass the PCRE_NOTEMPTY option to pcre_exec()
                      or pcre_dfa_exec(); if used twice, pass the
                      PCRE_NOTEMPTY_ATSTART option
         \Odd       set the size of the output vector passed to
                      pcre_exec() to dd (any number of digits)
         \P         pass the PCRE_PARTIAL_SOFT option to pcre_exec()
                      or pcre_dfa_exec(); if used twice, pass the
                      PCRE_PARTIAL_HARD option
         \Qdd       set the PCRE_MATCH_LIMIT_RECURSION limit to dd
                      (any number of digits)
         \R         pass the PCRE_DFA_RESTART option to pcre_dfa_exec()
         \S         output details of memory get/free calls during matching
         \Y         pass the PCRE_NO_START_OPTIMIZE option to pcre_exec()
                      or pcre_dfa_exec()
         \Z         pass the PCRE_NOTEOL option to pcre_exec()
                      or pcre_dfa_exec()
         \?         pass the PCRE_NO_UTF8_CHECK option to
                      pcre_exec() or pcre_dfa_exec()
         \>dd       start the match at offset dd (optional "-"; then
                      any number of digits); this sets the startoffset
                      argument for pcre_exec() or pcre_dfa_exec()
         \<cr>      pass the PCRE_NEWLINE_CR option to pcre_exec()
                      or pcre_dfa_exec()
         \<lf>      pass the PCRE_NEWLINE_LF option to pcre_exec()
                      or pcre_dfa_exec()
         \<crlf>    pass the PCRE_NEWLINE_CRLF option to pcre_exec()
                      or pcre_dfa_exec()
         \<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to pcre_exec()
                      or pcre_dfa_exec()
         \<any>     pass the PCRE_NEWLINE_ANY option to pcre_exec()
                      or pcre_dfa_exec()

       Note  that  \xhh  always  specifies  one byte, even in UTF-8 mode; this
       makes it possible to construct invalid UTF-8 sequences for testing pur-
       poses. On the other hand, \x{hh} is interpreted as a UTF-8 character in
       UTF-8 mode, generating more than one byte if the value is greater  than
       127. When not in UTF-8 mode, it generates one byte for values less than
       256, and causes an error for greater values.

       The escapes that specify line ending  sequences  are  literal  strings,
       exactly as shown. No more than one newline setting should be present in
       any data line.

       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  \M  is present, pcretest calls pcre_exec() several times, with dif-
       ferent values in the match_limit and  match_limit_recursion  fields  of
       the  pcre_extra  data structure, until it finds the minimum numbers for
       each parameter that allow pcre_exec() to complete. The match_limit num-
       ber  is  a  measure of the amount of 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. The match_limit_recursion number is a measure of how
       much stack (or, if PCRE is compiled with  NO_RECURSE,  how  much  heap)
       memory is needed to complete the match attempt.

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

       If  the /P modifier was present on the pattern, causing the POSIX wrap-
       per API to be used, the only option-setting  sequences  that  have  any
       effect  are  \B,  \N,  and  \Z,  causing  REG_NOTBOL, REG_NOTEMPTY, and
       REG_NOTEOL, respectively, to be passed to regexec().

       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 original
       UTF-8 rules of RFC 2279. This allows for  values  in  the  range  0  to
       0x7FFFFFFF.  Note  that not all of those are valid Unicode code points,
       or indeed valid UTF-8 characters according to the later  rules  in  RFC
       3629.


THE ALTERNATIVE MATCHING FUNCTION

       By   default,  pcretest  uses  the  standard  PCRE  matching  function,
       pcre_exec() to match each data line. From release 6.0, PCRE supports an
       alternative  matching  function,  pcre_dfa_test(),  which operates in a
       different way, and has some restrictions. The differences  between  the
       two functions are described in the pcrematching documentation.

       If  a data line contains the \D escape sequence, or if the command line
       contains the -dfa option, the alternative matching function is  called.
       This function finds all possible matches at a given point. If, however,
       the \F escape sequence is present in the data line, it stops after  the
       first match is found. This is always the shortest possible match.


DEFAULT OUTPUT FROM PCRETEST

       This  section  describes  the output when the normal matching function,
       pcre_exec(), is being used.

       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. Otherwise, it outputs "No  match"  when  the
       return is PCRE_ERROR_NOMATCH, and "Partial match:" followed by the par-
       tially matching substring when pcre_exec() returns  PCRE_ERROR_PARTIAL.
       (Note  that  this is the entire substring that was inspected during the
       partial match; it may include characters before the actual match  start
       if  a  lookbehind assertion, \K, \b, or \B was involved.) For any other
       return, pcretest outputs the PCRE negative error  number  and  a  short
       descriptive  phrase.  If  the error is a failed UTF-8 string check, the
       byte offset of the start of the failing character and the  reason  code
       are  also  output,  provided  that  the size of the output vector is at
       least two. Here is an example of an interactive pcretest run.

         $ pcretest
         PCRE version 8.13 2011-04-30

           re> /^abc(\d+)/
         data> abc123
          0: abc123
          1: 123
         data> xyz
         No match

       Unset capturing substrings that are not followed by one that is set are
       not returned by pcre_exec(), and are not shown by pcretest. In the fol-
       lowing example, there are two capturing substrings, but when the  first
       data  line  is  matched,  the  second, unset substring is not shown. An
       "internal" unset substring is shown as "<unset>",  as  for  the  second
       data line.

           re> /(a)|(b)/
         data> a
          0: a
          1: a
         data> b
          0: b
          1: <unset>
          2: b

       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.  See below for the definition of non-printing characters.
       If the pattern has the /+ modifier, the output for substring 0 is  fol-
       lowed  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. Here is an
       example of a failure message (the offset 4 that is specified by \>4  is
       past the end of the subject string):

           re> /xyz/
         data> xyz\>4
         Error -24 (bad offset value)

       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 whereas 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 (or  \r,  \r\n,
       etc., depending on the newline sequence setting).


OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION

       When  the  alternative  matching function, pcre_dfa_exec(), is used (by
       means of the \D escape sequence or the -dfa command line  option),  the
       output  consists  of  a list of all the matches that start at the first
       point in the subject where there is at least one match. For example:

           re> /(tang|tangerine|tan)/
         data> yellow tangerine\D
          0: tangerine
          1: tang
          2: tan

       (Using the normal matching function on this data  finds  only  "tang".)
       The  longest matching string is always given first (and numbered zero).
       After a PCRE_ERROR_PARTIAL return, the output is "Partial match:", fol-
       lowed  by  the  partially  matching  substring.  (Note that this is the
       entire substring that was inspected during the partial  match;  it  may
       include characters before the actual match start if a lookbehind asser-
       tion, \K, \b, or \B was involved.)

       If /g is present on the pattern, the search for further matches resumes
       at the end of the longest match. For example:

           re> /(tang|tangerine|tan)/g
         data> yellow tangerine and tangy sultana\D
          0: tangerine
          1: tang
          2: tan
          0: tang
          1: tan
          0: tan

       Since  the  matching  function  does not support substring capture, the
       escape sequences that are concerned with captured  substrings  are  not
       relevant.


RESTARTING AFTER A PARTIAL MATCH

       When the alternative matching function has given the PCRE_ERROR_PARTIAL
       return, indicating that the subject partially matched the pattern,  you
       can  restart  the match with additional subject data by means of the \R
       escape sequence. For example:

           re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/
         data> 23ja\P\D
         Partial match: 23ja
         data> n05\R\D
          0: n05

       For further information about partial  matching,  see  the  pcrepartial
       documentation.


CALLOUTS

       If  the pattern contains any callout requests, pcretest's callout func-
       tion is called during matching. This works  with  both  matching  func-
       tions. By default, the called function displays the callout number, the
       start and current positions in the text at the callout  time,  and  the
       next pattern item to be tested. For example, the output

         --->pqrabcdef
           0    ^  ^     \d

       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 of the data, and when the next pattern item was
       \d. Just one circumflex is output if the start  and  current  positions
       are the same.

       Callouts numbered 255 are assumed to be automatic callouts, inserted as
       a result of the /C pattern modifier. In this case, instead  of  showing
       the  callout  number, the offset in the pattern, preceded by a plus, is
       output. For example:

           re> /\d?[A-E]\*/C
         data> E*
         --->E*
          +0 ^      \d?
          +3 ^      [A-E]
          +8 ^^     \*
         +10 ^ ^
          0: E*

       If a pattern contains (*MARK) items, an additional line is output when-
       ever  a  change  of  latest mark is passed to the callout function. For
       example:

           re> /a(*MARK:X)bc/C
         data> abc
         --->abc
          +0 ^       a
          +1 ^^      (*MARK:X)
         +10 ^^      b
         Latest Mark: X
         +11 ^ ^     c
         +12 ^  ^
          0: abc

       The mark changes between matching "a" and "b", but stays the  same  for
       the  rest  of  the match, so nothing more is output. If, as a result of
       backtracking, the mark reverts to being unset, the  text  "<unset>"  is
       output.

       The  callout  function  in pcretest returns zero (carry on matching) by
       default, but you can use a \C item in a data line (as described  above)
       to change this and other parameters of the callout.

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


NON-PRINTING CHARACTERS

       When  pcretest is outputting text in the compiled version of a pattern,
       bytes other than 32-126 are always treated as  non-printing  characters
       are are therefore shown as hex escapes.

       When  pcretest  is  outputting text that is a matched part of a subject
       string, it behaves in the same way, unless a different locale has  been
       set  for  the  pattern  (using  the  /L  modifier).  In  this case, the
       isprint() function to distinguish printing and non-printing characters.


SAVING AND RELOADING COMPILED PATTERNS

       The facilities described in this section are  not  available  when  the
       POSIX  interface  to  PCRE  is being used, that is, when the /P pattern
       modifier is specified.

       When the POSIX interface is not in use, you can cause pcretest to write
       a  compiled  pattern to a file, by following the modifiers with > and a
       file name.  For example:

         /pattern/im >/some/file

       See the pcreprecompile documentation for a discussion about saving  and
       re-using compiled patterns.

       The  data  that  is  written  is  binary. The first eight bytes are the
       length of the compiled pattern data  followed  by  the  length  of  the
       optional  study  data,  each  written as four bytes in big-endian order
       (most significant byte first). If there is no study  data  (either  the
       pattern was not studied, or studying did not return any data), the sec-
       ond length is zero. The lengths are followed by an exact  copy  of  the
       compiled pattern. If there is additional study data, this follows imme-
       diately after the compiled pattern. After writing  the  file,  pcretest
       expects to read a new pattern.

       A  saved  pattern  can  be reloaded into pcretest by specifying < and a
       file name instead of a pattern. The name of the file must not contain a
       < character, as otherwise pcretest will interpret the line as a pattern
       delimited by < characters.  For example:

          re> </some/file
         Compiled pattern loaded from /some/file
         No study data

       When the pattern has been loaded, pcretest proceeds to read data  lines
       in the usual way.

       You  can copy a file written by pcretest to a different host and reload
       it there, even if the new host has opposite endianness to  the  one  on
       which  the pattern was compiled. For example, you can compile on an i86
       machine and run on a SPARC machine.

       File names for saving and reloading can be absolute  or  relative,  but
       note  that the shell facility of expanding a file name that starts with
       a tilde (~) is not available.

       The ability to save and reload files in pcretest is intended for  test-
       ing  and experimentation. It is not intended for production use because
       only a single pattern can be written to a file. Furthermore,  there  is
       no  facility  for  supplying  custom  character  tables  for use with a
       reloaded pattern. If the original  pattern  was  compiled  with  custom
       tables,  an  attempt to match a subject string using a reloaded pattern
       is likely to cause pcretest to crash.  Finally, if you attempt to  load
       a file that is not in the correct format, the result is undefined.


SEE ALSO

       pcre(3),  pcreapi(3),  pcrecallout(3), pcrematching(3), pcrepartial(d),
       pcrepattern(3), pcreprecompile(3).


AUTHOR

       Philip Hazel
       University Computing Service
       Cambridge CB2 3QH, England.


REVISION

       Last updated: 01 August 2011
       Copyright (c) 1997-2011 University of Cambridge.
