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PCRETEST(1)                                                        PCRETEST(1)

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


       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.


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

       -C        Output  the version number of the PCRE library, and all available information about the optional fea-
                 tures 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

       -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() repeatedly with different lim-

       -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 subexpressions
                 for pcre_exec() or 22 different matches for pcre_dfa_exec(). The vector size can be changed for indi-
                 vidual 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 or -s+ Behave  as  if each pattern has the /S modifier; in other words, force each pattern to be studied. If
                 -s+ is used, the PCRE_STUDY_JIT_COMPILE flag is passed to pcre_study(),  causing  just-in-time  opti-
                 mization  to be set up if it is available. 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 neither -i nor -d is present on the command line. This behaviour
                 means that the output from tests that are run with and without -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 specific patterns that should never be studied  (see
                 the /S pattern modifier below).

       -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 -m with -t, because you will then get the size output  a  zillion
                 times,  and  the timing will be distorted. 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 iterate 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.


       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 expres-
       sion, and continues with any number 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:


       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. It is possible to include the delimiter
       within the pattern by escaping it, for example


       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 followed by
       a backslash, for example,


       then a backslash is added to the end of the pattern. This is done to provide a way of testing the error  condi-
       tion that arises if a pattern finishes with a backslash, because


       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.


       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_compile() is called. These four modifier letters have the same effect  as  they  do  in
       Perl. For example:


       The  following table shows additional modifiers for setting PCRE compile-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 end-
       ing sequence:


       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 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_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() function. Normally, the start  offset
       is advanced by one character, but if the newline convention recognizes CRLF as a newline, and the current char-
       acter 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 con-
       tains multiple copies of the same substring. If the + modifier appears twice, the same action is taken for cap-
       tured  substrings.  In  each case the remainder is output on the following line with a plus character following
       the capture number. Note that this modifier must not immediately follow the /S modifier because /S+ has another

       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  (corresponding
       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 output a representation of the compiled  byte
       code  after  compilation.  Normally  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 modi-

       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  inter-
       face to PCRE is being used, that is, when the /P pattern modifier is specified. See also the section about sav-
       ing 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 output.

       The /K modifier requests pcretest to show names from backtracking control verbs that are returned from calls to
       pcre_exec().  It  causes pcretest to create a pcre_extra block if one has not already been created 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,


       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 compiled pattern to be output. This  does  not
       include the size of the pcre block; it is just the actual compiled data. If the pattern is successfully studied
       with the PCRE_STUDY_JIT_COMPILE option, the size of the JIT compiled code is also 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.

       If the /S modifier is immediately followed by a +  character,  the  call  to  pcre_study()  is  made  with  the
       PCRE_STUDY_JIT_COMPILE option, requesting just-in-time optimization support if it is available. Note that there
       is also a /+ modifier; it must not be given immediately after /S because this will be  misinterpreted.  If  JIT
       studying  is  successful,  it will automatically be used when pcre_exec() is run, except when incompatible run-
       time options are specified. These include the partial matching options; a complete list is given in the pcrejit
       documentation. See also the \J escape sequence below for a way of setting the size of the JIT stack.

       The /T modifier must be followed by a single digit. It causes a specific 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
         1   a set of tables defining ISO 8859 characters

       In table 1, some characters whose codes are greater than 128 are identified 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.


       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 "ordinary" 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
         \C-        do not supply a callout function
         \C!n       return 1 instead of 0 when callout number n is
         \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)
         \Jdd       set up a JIT stack of dd kilobytes maximum (any
                      number of digits)
         \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 purposes. 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 back-
       slash, it is ignored. This gives a way of passing an empty line as data, since a real empty line terminates the
       data input.

       The  \J  escape  provides a way of setting the maximum stack size that is used by the just-in-time optimization
       code. It is ignored if JIT optimization is not being used. Providing a stack that is larger  than  the  default
       32K is necessary only for very complicated patterns.

       If  \M  is  present,  pcretest  calls  pcre_exec()  several times, with different 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 without error. Because this is testing a specific feature of the
       normal interpretive pcre_exec() execution, the use of any JIT optimization that might have been set up  by  the
       /S+ qualifier of -s+ option is disabled.

       The  match_limit number 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 wrapper 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  pat-
       tern.  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 charac-
       ters according to the later rules in RFC 3629.


       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

       If  a  data line contains the \D escape sequence, or if the command line contains the -dfa option, the alterna-
       tive 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.


       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 partially 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 following 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 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. 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  func-
       tion) is given in parentheses 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 newlines can be included in data by means of the \n  escape  (or  \r,  \r\n,  etc.,
       depending on the newline sequence setting).


       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:", followed 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 assertion, \K,  \b,  or  \B  was

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

           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.


       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.


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

           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

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

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

           re> /a(*MARK:X)bc/C
         data> 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 complicated regular expressions. For further
       information about callouts, see the pcrecallout documentation.


       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.


       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  fol-
       lowing 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.  Note that
       if the pattern was successfully studied with JIT optimization, the JIT data cannot be saved.

       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 second length is zero. The lengths are followed by an exact copy of the compiled pattern. If there is addi-
       tional study data, this (excluding any JIT data) follows immediately 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

       If  the  pattern  was  previously  studied  with  the JIT optimization, the JIT information cannot be saved and
       restored, and so is lost. When the pattern has been loaded, pcretest proceeds to read data lines in  the  usual

       You can copy a file written by pcretest to a different host and reload it there, even if the new host has oppo-
       site 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  testing  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


       pcre(3),  pcreapi(3),  pcrecallout(3),  pcrejit,  pcrematching(3),  pcrepartial(d), pcrepattern(3), pcreprecom-


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


       Last updated: 02 December 2011
       Copyright (c) 1997-2011 University of Cambridge.