pcretest(1) — Linux manual page


PCRETEST(1)                General Commands Manual               PCRETEST(1)

NAME         top

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

SYNOPSIS         top

       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

       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


       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.

PCRE's 8-BIT, 16-BIT AND 32-BIT LIBRARIES         top

       From release 8.30, two separate PCRE libraries can be built. The
       original 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


       -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)
                 modifier; the internal form is output after compilation.

       -C        Output the version number of the PCRE library, and all
                 available 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
                                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
                 disable 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 different 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 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,
                 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 follows:

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

                 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 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 separate item on the command line). For example, "-t
                 1000" iterates 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.

DESCRIPTION         top

       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

       The program handles any number of sets of input on a single input
       file. Each set starts with a regular expression, and continues with
       any number of data lines to be matched against 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 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


       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 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 expression.


       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 modifiers. White space may appear between the final pattern
       delimiter and the first modifier, and between the modifiers
       themselves. For reference, 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
       compile-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
       output in hex without the curly brackets.

       Full details of the PCRE options are given in the pcreapi

   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[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() function. 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

       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 +
       modifier 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 meanings.

       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 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 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 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 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[16|32]_fullinfo()
       after compiling 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
       control 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 example,


       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

       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

       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

       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 documentation. 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
       specific set of built-in character tables to be passed to
       pcre[16|32]_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. This supports only the 8-bit library.
       When /P is set, the following modifiers set options for the regcomp()

         /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 mistake; 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 modifiers. 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 Unicode 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 example:

         < 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.

DATA LINES         top

       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
         \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
                      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
       hexadecimal digits inside the braces; invalid values provoke error

       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

       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
       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[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 numbers for each parameter that allow pcre[16|32]_exec() to
       complete without error. Because this is testing a specific feature of
       the normal interpretive pcre[16|32]_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[16|32]_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().


       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

       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


       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 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[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 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 function) 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[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 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 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:

         data> 23ja\P\D
         Partial match: 23ja
         data> n05\R\D
          0: n05

       For further information about partial matching, see the pcrepartial

CALLOUTS         top

       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 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
       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

       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


       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

       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 additional study data, this
       (excluding any JIT data) follows immediately after the compiled
       pattern. After writing the file, pcretest expects to read a new

       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 <
       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 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 reloaded.

       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 undefined.

SEE ALSO         top

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

AUTHOR         top

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

REVISION         top

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

COLOPHON         top

       This page is part of the PCRE (Perl Compatible Regular Expressions)
       project.  Information about the project can be found at 
       ⟨http://www.pcre.org/⟩.  If you have a bug report for this manual
       page, see ⟨http://bugs.exim.org/enter_bug.cgi?product=PCRE⟩.  This
       page was obtained from the tarball pcre-8.44.tar.gz fetched from
       ⟨ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/⟩ on
       2020-11-01.  If you discover any rendering problems in this HTML ver‐
       sion of the page, or you believe there is a better or more up-to-date
       source for the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original man‐
       ual page), send a mail to man-pages@man7.org

PCRE 8.44                     10 February 2020                   PCRETEST(1)

Pages that refer to this page: pcregrep(1)