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PCRETEST(1)                 General Commands Manual                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 , pcre16 and pcre32 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.

       As  PCRE has evolved, it has acquired many different features, and as a
       result, pcretest now has rather a lot of obscure  options  for  testing
       every possible feature. Some of these options are specifically designed
       for use in conjunction with the test script and  data  files  that  are
       distributed  as  part of PCRE, and are unlikely to be of use otherwise.
       They are all documented here, but without much justification.


       Input to pcretest is processed line by line, either by  calling  the  C
       library's fgets() function, or via the libreadline library (see below).
       In Unix-like environments, fgets() treats any bytes other than  newline
       as  data characters. However, in some Windows environments character 26
       (hex 1A) causes an immediate end of file, and no further data is  read.
       For  maximum  portability,  therefore,  it  is safest to use only ASCII
       characters in pcretest input files.

       The input is processed using using C's string functions,  so  must  not
       contain  binary  zeroes, even though in Unix-like environments, fgets()
       treats any bytes other than newline as data characters.


       From release 8.30, two separate PCRE libraries can be built. The origi‐
       nal  one  supports  8-bit  character  strings, whereas the newer 16-bit
       library supports  character  strings  encoded  in  16-bit  units.  From
       release  8.32,  a  third  library  can  be  built, supporting character
       strings encoded in 32-bit units. The pcretest program can  be  used  to
       test all three libraries. However, it is itself still an 8-bit program,
       reading 8-bit input and writing 8-bit output.  When testing the  16-bit
       or  32-bit  library, the patterns and data strings are converted to 16-
       or 32-bit format before being passed to  the  PCRE  library  functions.
       Results are converted to 8-bit for output.

       References to functions and structures of the form pcre[16|32]_xx below
       mean "pcre_xx when using the 8-bit library, pcre16_xx  when  using  the
       16-bit library, or pcre32_xx when using the 32-bit library".


       -8        If the 8-bit library has been built, this option causes it to
                 be used (this is the default). If the 8-bit library  has  not
                 been built, this option causes an error.

       -16       If  the  16-bit library has been built, this option causes it
                 to be used. If only the 16-bit library has been  built,  this
                 is  the  default.  If  the 16-bit library has not been built,
                 this option causes an error.

       -32       If the 32-bit library has been built, this option  causes  it
                 to  be  used. If only the 32-bit library has been built, this
                 is the default. If the 32-bit library  has  not  been  built,
                 this option causes an error.

       -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  with  zero  exit  code.  All  other
                 options are ignored.

       -C option Output  information  about a specific build-time option, then
                 exit. This functionality is intended for use in scripts  such
                 as  RunTest.  The  following options output the value and set
                 the exit code as indicated:

                   ebcdic-nl  the code for LF (= NL) in an EBCDIC environment:
                                0x15 or 0x25
                                0 if used in an ASCII environment
                                exit code is always 0
                   linksize   the configured internal link size (2, 3, or 4)
                                exit code is set to the link size
                   newline    the default newline setting:
                                CR, LF, CRLF, ANYCRLF, or ANY
                                exit code is always 0
                   bsr        the default setting for what \R matches:
                                ANYCRLF or ANY
                                exit code is always 0

                 The following options output 1 for true or 0 for  false,  and
                 set the exit code to the same value:

                   ebcdic     compiled for an EBCDIC environment
                   jit        just-in-time support is available
                   pcre16     the 16-bit library was built
                   pcre32     the 32-bit library was built
                   pcre8      the 8-bit library was built
                   ucp        Unicode property support is available
                   utf        UTF-8 and/or UTF-16 and/or UTF-32 support
                                is available

                 If  an  unknown  option is given, an error message is output;
                 the exit code is 0.

       -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[16|32]_dfa_exec(), to be used instead  of  the  standard
                 pcre[16|32]_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[16|32]_exec()
                 repeatedly 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. The size is given in bytes for both libraries.

       -O        Behave  as  if each pattern has the /O modifier, that is dis‐
                 able auto-possessification for all patterns.

       -o osize  Set the number of elements in the output vector that is  used
                 when  calling pcre[16|32]_exec() or pcre[16|32]_dfa_exec() to
                 be osize. The default value is 45, which  is  enough  for  14
                 capturing subexpressions for pcre[16|32]_exec() or 22 differ‐
                 ent matches for pcre[16|32]_dfa_exec().  The vector size  can
                 be  changed  for individual 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. This option can be  used  only
                 with the 8-bit library.

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

       -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,  all
                 the  JIT  compile  options are passed to pcre[16|32]_study(),
                 causing just-in-time optimization to  be  set  up  if  it  is
                 available,  for  both full and partial matching. Specific JIT
                 compile options can be selected by following -s+ with a digit
                 in  the  range 1 to 7, which selects the JIT compile modes as

                   1  normal match only
                   2  soft partial match only
                   3  normal match and soft partial match
                   4  hard partial match only
                   6  soft and hard partial match
                   7  all three modes (default)

                 If -s++ is used instead of -s+ (with or without  a  following
                 digit),  the  text  "(JIT)" is added to the first output line
                 after a match or no match when JIT-compiled code was actually

                 Note  that  there  are  pattern options that can override -s,
                 either specifying no studying at all, or suppressing JIT com‐

                 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 spe‐
                 cific patterns that should never be studied (see the /S  pat‐
                 tern modifier below).

       -t        Run  each  compile, study, and match many times with a timer,
                 and output the resulting times per compile, study,  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 sepa‐
                 rate  item on the command line). For example, "-t 1000" iter‐
                 ates 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.

       -T -TM    These  behave like -t and -tm, but in addition, at the end of
                 a run, the total times for all compiles, studies, and matches
                 are output.


       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

       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 that 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

       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 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


       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,


       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


       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


       A  pattern may be followed by any number of modifiers, which are mostly
       single characters, though some of these can  be  qualified  by  further
       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 modi‐
       fiers. White space may appear between the final pattern  delimiter  and
       the  first  modifier,  and between the modifiers themselves. For refer‐
       ence, here is a complete list of  modifiers.  They  fall  into  several
       groups that are described in detail in the following sections.

         /8              set UTF mode
         /9              set PCRE_NEVER_UTF (locks out UTF mode)
         /?              disable UTF validity check
         /+              show remainder of subject after match
         /=              show all captures (not just those that are set)

         /A              set PCRE_ANCHORED
         /B              show compiled code
         /C              set PCRE_AUTO_CALLOUT
         /D              same as /B plus /I
         /E              set PCRE_DOLLAR_ENDONLY
         /F              flip byte order in compiled pattern
         /f              set PCRE_FIRSTLINE
         /G              find all matches (shorten string)
         /g              find all matches (use startoffset)
         /I              show information about pattern
         /i              set PCRE_CASELESS
         /J              set PCRE_DUPNAMES
         /K              show backtracking control names
         /L              set locale
         /M              show compiled memory size
         /m              set PCRE_MULTILINE
         /N              set PCRE_NO_AUTO_CAPTURE
         /O              set PCRE_NO_AUTO_POSSESS
         /P              use the POSIX wrapper
         /Q              test external stack check function
         /S              study the pattern after compilation
         /s              set PCRE_DOTALL
         /T              select character tables
         /U              set PCRE_UNGREEDY
         /W              set PCRE_UCP
         /X              set PCRE_EXTRA
         /x              set PCRE_EXTENDED
         /Y              set PCRE_NO_START_OPTIMIZE
         /Z              don't show lengths in /B output

         /<any>          set PCRE_NEWLINE_ANY
         /<anycrlf>      set PCRE_NEWLINE_ANYCRLF
         /<cr>           set PCRE_NEWLINE_CR
         /<crlf>         set PCRE_NEWLINE_CRLF
         /<lf>           set PCRE_NEWLINE_LF
         /<bsr_anycrlf>  set PCRE_BSR_ANYCRLF
         /<bsr_unicode>  set PCRE_BSR_UNICODE
         /<JS>           set PCRE_JAVASCRIPT_COMPAT

   Perl-compatible modifiers

       The /i, /m, /s, and /x modifiers set the PCRE_CASELESS, PCRE_MULTILINE,
       PCRE_DOTALL,   or    PCRE_EXTENDED    options,    respectively,    when
       pcre[16|32]_compile()  is  called. These four modifier letters have the
       same effect as they do in Perl. For example:


   Modifiers for other PCRE options

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

         /8              PCRE_UTF8           ) when using the 8-bit
         /?              PCRE_NO_UTF8_CHECK  )   library

         /8              PCRE_UTF16          ) when using the 16-bit
         /?              PCRE_NO_UTF16_CHECK )   library

         /8              PCRE_UTF32          ) when using the 32-bit
         /?              PCRE_NO_UTF32_CHECK )   library

         /9              PCRE_NEVER_UTF
         /A              PCRE_ANCHORED
         /C              PCRE_AUTO_CALLOUT
         /E              PCRE_DOLLAR_ENDONLY
         /f              PCRE_FIRSTLINE
         /J              PCRE_DUPNAMES
         /N              PCRE_NO_AUTO_CAPTURE
         /O              PCRE_NO_AUTO_POSSESS
         /U              PCRE_UNGREEDY
         /W              PCRE_UCP
         /X              PCRE_EXTRA
         /Y              PCRE_NO_START_OPTIMIZE
         /<any>          PCRE_NEWLINE_ANY
         /<anycrlf>      PCRE_NEWLINE_ANYCRLF
         /<cr>           PCRE_NEWLINE_CR
         /<crlf>         PCRE_NEWLINE_CRLF
         /<lf>           PCRE_NEWLINE_LF
         /<bsr_anycrlf>  PCRE_BSR_ANYCRLF
         /<bsr_unicode>  PCRE_BSR_UNICODE
         /<JS>           PCRE_JAVASCRIPT_COMPAT

       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:


       As well as turning on  the  PCRE_UTF8/16/32  option,  the  /8  modifier
       causes  all  non-printing  characters  in  output strings to be printed
       using the \x{hh...} notation. Otherwise, those less than 0x100 are out‐
       put in hex without the curly brackets.

       Full  details  of  the PCRE options are given in the pcreapi documenta‐

   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[16|32]_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[16|32]_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. Note that  this  modifier  must
       not  immediately follow the /S modifier because /S+ and /S++ have other

       The /= modifier requests that the  values  of  all  potential  captured
       parentheses  be  output after a match. By default, only those up to the
       highest one actually used in the match are output (corresponding to the
       return code from pcre[16|32]_exec()). Values in the offsets vector cor‐
       responding to higher numbers should be set to -1, and these are  output
       as  "<unset>".  This modifier gives a way of checking that this is hap‐

       The /B modifier is a debugging feature. It requests that pcretest  out‐
       put  a  representation of the compiled 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 fea‐
       ture 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  2-byte
       and 4-byte fields in the compiled pattern. This facility is for testing
       the feature in PCRE that allows it to execute patterns that  were  com‐
       piled on a host with a different endianness. This feature is not avail‐
       able 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[16|32]_fullinfo()  after  com‐
       piling  a  pattern.  If the pattern is studied, the results of that are
       also output. In this output, the word "char" means a non-UTF character,
       that  is,  the  value  of a single data item (8-bit, 16-bit, or 32-bit,
       depending on the library that is being tested).

       The /K modifier requests pcretest to show names from backtracking  con‐
       trol  verbs  that  are  returned  from  calls to pcre[16|32]_exec(). It
       causes pcretest to create a pcre[16|32]_extra  block  if  one  has  not
       already  been  created by a call to pcre[16|32]_study(), and to set the
       PCRE_EXTRA_MARK flag and the mark field  within  it,  every  time  that
       pcre[16|32]_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


       For this reason, it must be the last modifier. The given locale is set,
       pcre[16|32]_maketables()  is  called to build a set of character tables
       for the locale, and this is then passed to  pcre[16|32]_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 in bytes of the memory block used to
       hold the compiled pattern to be output. This does not include the  size
       of  the  pcre[16|32] 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.

       The /Q modifier is used to test the use of pcre_stack_guard. It must be
       followed by '0' or '1', specifying the return code to be given from  an
       external  function  that  is passed to PCRE and used for stack checking
       during compilation (see the pcreapi documentation for details).

       The /S modifier causes  pcre[16|32]_study()  to  be  called  after  the
       expression  has been compiled, and the results used when the expression
       is matched. There are a number of qualifying characters that may follow
       /S.  They may appear in any order.

       If /S is followed by an exclamation mark, pcre[16|32]_study() is called
       with the PCRE_STUDY_EXTRA_NEEDED option, causing it always to return  a
       pcre_extra block, even when studying discovers no useful information.

       If /S is followed by a second S character, 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  followed  by  a  +  character,  the  call  to
       pcre[16|32]_study()  is made with all the JIT study options, requesting
       just-in-time optimization support if it is available, for  both  normal
       and  partial matching. If you want to restrict the JIT compiling modes,
       you can follow /S+ with a digit in the range 1 to 7:

         1  normal match only
         2  soft partial match only
         3  normal match and soft partial match
         4  hard partial match only
         6  soft and hard partial match
         7  all three modes (default)

       If /S++ is used instead of /S+ (with or without a following digit), the
       text  "(JIT)"  is  added  to  the first output line after a match or no
       match when JIT-compiled code was actually used.

       Note that there is also an independent /+  modifier;  it  must  not  be
       given immediately after /S or /S+ because this will be misinterpreted.

       If JIT studying is successful, the compiled JIT code will automatically
       be used when pcre[16|32]_exec() is run, except when  incompatible  run-
       time  options are specified. For more details, see the pcrejit documen‐
       tation. See also the \J escape sequence below for a way of setting  the
       size of the JIT stack.

       Finally,  if  /S  is  followed by a minus character, JIT compilation is
       suppressed, even if it was requested externally by the -s command  line
       option.  This makes it possible to specify that JIT is never to be used
       for certain patterns.

       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[16|32]_com‐
       pile(). 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 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. This supports only the 8-bit library. When
       /P is set, the following modifiers set options for the regcomp()  func‐

         /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

   Locking out certain modifiers

       PCRE can be compiled with or without support for certain features  such
       as  UTF-8/16/32  or Unicode properties. Accordingly, the standard tests
       are split up into a number of different files  that  are  selected  for
       running  depending  on  which features are available. When updating the
       tests, it is all too easy to put a new test into the wrong file by mis‐
       take;  for example, to put a test that requires UTF support into a file
       that is used when it is not available. To help detect such mistakes  as
       early  as  possible, there is a facility for locking out specific modi‐
       fiers. If an input line for pcretest starts with the string "< forbid "
       the  following  sequence  of characters is taken as a list of forbidden
       modifiers. For example, in the test files that must not use UTF or Uni‐
       code property support, this line appears:

         < forbid 8W

       This  locks out the /8 and /W modifiers. An immediate error is given if
       they are subsequently encountered. If the character string  contains  <
       but  not  >,  all  the  multi-character modifiers that begin with < are
       locked out. Otherwise, such modifiers must be  explicitly  listed,  for

         < forbid <JS><cr>

       There must be a single space between < and "forbid" for this feature to
       be recognised. If there is not, the line is  interpreted  either  as  a
       request  to  re-load  a pre-compiled pattern (see "SAVING AND RELOADING
       COMPILED PATTERNS" below) or, if there is a another < character,  as  a
       pattern that uses < as its delimiter.


       Before  each  data  line  is  passed to pcre[16|32]_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 or 16-bit or 32-bit mode
         \o{dd...}  octal character (any number of octal digits}
         \xhh       hexadecimal byte (up to 2 hex digits)
         \x{hh...}  hexadecimal character (any number of hex digits)
         \A         pass the PCRE_ANCHORED option to pcre[16|32]_exec()
                      or pcre[16|32]_dfa_exec()
         \B         pass the PCRE_NOTBOL option to pcre[16|32]_exec()
                      or pcre[16|32]_dfa_exec()
         \Cdd       call pcre[16|32]_copy_substring() for substring dd
                      after a successful match (number less than 32)
         \Cname     call pcre[16|32]_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[16|32]_dfa_exec() match function
         \F         only shortest match for pcre[16|32]_dfa_exec()
         \Gdd       call pcre[16|32]_get_substring() for substring dd
                      after a successful match (number less than 32)
         \Gname     call pcre[16|32]_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[16|32]_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[16|32]_exec()
                      or pcre[16|32]_dfa_exec(); if used twice, pass the
                      PCRE_NOTEMPTY_ATSTART option
         \Odd       set the size of the output vector passed to
                      pcre[16|32]_exec() to dd (any number of digits)
         \P         pass the PCRE_PARTIAL_SOFT option to pcre[16|32]_exec()
                      or pcre[16|32]_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[16|32]_dfa_exec()
         \S         output details of memory get/free calls during matching
         \Y            pass    the    PCRE_NO_START_OPTIMIZE     option     to
                      or pcre[16|32]_dfa_exec()
         \Z         pass the PCRE_NOTEOL option to pcre[16|32]_exec()
                      or pcre[16|32]_dfa_exec()
         \?         pass the PCRE_NO_UTF[8|16|32]_CHECK option to
                      pcre[16|32]_exec() or pcre[16|32]_dfa_exec()
         \>dd       start the match at offset dd (optional "-"; then
                      any number of digits); this sets the startoffset
                      argument         for        pcre[16|32]_exec()        or
         \<cr>      pass the PCRE_NEWLINE_CR option to pcre[16|32]_exec()
                      or pcre[16|32]_dfa_exec()
         \<lf>      pass the PCRE_NEWLINE_LF option to pcre[16|32]_exec()
                      or pcre[16|32]_dfa_exec()
         \<crlf>    pass the PCRE_NEWLINE_CRLF option to pcre[16|32]_exec()
                      or pcre[16|32]_dfa_exec()
         \<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to pcre[16|32]_exec()
                      or pcre[16|32]_dfa_exec()
         \<any>     pass the PCRE_NEWLINE_ANY option to pcre[16|32]_exec()
                      or pcre[16|32]_dfa_exec()

       The use of \x{hh...} is not dependent on the use of the /8 modifier  on
       the  pattern. It is recognized always. There may be any number of hexa‐
       decimal digits inside the braces; invalid  values  provoke  error  mes‐

       Note  that  \xhh  specifies one byte rather than one character 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 testing the 8-bit library not in UTF-8 mode,
       \x{hh} generates one byte for values less than 256, and causes an error
       for greater values.

       In UTF-16 mode, all 4-digit \x{hhhh} values are accepted. This makes it
       possible to construct invalid UTF-16 sequences for testing purposes.

       In UTF-32 mode, all 4- to 8-digit \x{...}  values  are  accepted.  This
       makes  it  possible  to  construct invalid UTF-32 sequences for testing

       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.

       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  opti‐
       mization  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[16|32]_exec() several times, with
       different values in the match_limit and match_limit_recursion fields of
       the pcre[16|32]_extra data structure, until it finds the  minimum  num‐
       bers for each parameter that allow pcre[16|32]_exec() to complete with‐
       out error. Because this is testing a specific  feature  of  the  normal
       interpretive pcre[16|32]_exec() execution, the use of any JIT optimiza‐
       tion that might have been set up by the /S+ qualifier of -s+ option  is

       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

       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[16|32]_exec()  for  the  line  in  which  it

       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().


       By  default,  pcretest  uses  the  standard  PCRE  matching   function,
       pcre[16|32]_exec()  to  match  each  data  line.  PCRE also supports an
       alternative matching function, pcre[16|32]_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 used.
       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[16|32]_exec(), is being used.

       When a match succeeds, pcretest outputs the list of captured substrings
       that pcre[16|32]_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[16|32]_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  string check, the 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

         $ 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[16|32]_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
       \xhh escapes if the value is less than 256 and UTF  mode  is  not  set.
       Otherwise they are output as \x{hh...} escapes. See below for the defi‐
       nition 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 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).


       When the alternative matching function, pcre[16|32]_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 exam‐

           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


       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


       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:

           0    ^  ^     \d

       This output 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*
          +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

           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

       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.


       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 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.  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 sec‐
       ond length is zero. The lengths are followed by an exact  copy  of  the
       compiled  pattern.  If  there is additional 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. There must be no space  between  <  and
       the  file  name,  which  must  not  contain a < character, as otherwise
       pcretest will interpret the line as a pattern delimited  by  <  charac‐
       ters. 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 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. When a pattern is reloaded on a
       host with different endianness, the confirmation message is changed to:

         Compiled pattern (byte-inverted) loaded from /some/file

       The test suite contains some saved pre-compiled patterns with different
       endianness.  These  are  reloaded  using "<!" instead of just "<". This
       suppresses the "(byte-inverted)" text so that the output is the same on
       all  hosts.  It  also forces debugging output once the pattern has been

       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.


       pcre(3),  pcre16(3),  pcre32(3),  pcreapi(3),  pcrecallout(3), pcrejit,
       pcrematching(3), pcrepartial(d), pcrepattern(3), pcreprecompile(3).


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


       Last updated: 10 February 2020
       Copyright (c) 1997-2020 University of Cambridge.

PCRE 8.44                      10 February 2020                    PCRETEST(1)
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