pcre2test(1) — Linux manual page


PCRE2TEST(1)             General Commands Manual            PCRE2TEST(1)

NAME         top

       pcre2test - a program for testing Perl-compatible regular

SYNOPSIS         top

       pcre2test [options] [input file [output file]]

       pcre2test is a test program for the PCRE2 regular expression
       libraries, 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 pcre2pattern documentation. For details of the PCRE2 library
       function calls and their options, see the pcre2api documentation.

       The input for pcre2test is a sequence of regular expression
       patterns and subject strings to be matched. There are also
       command lines for setting defaults and controlling some special
       actions. The output shows the result of each match attempt.
       Modifiers on external or internal command lines, the patterns,
       and the subject lines specify PCRE2 function options, control how
       the subject is processed, and what output is produced.

       There are many obscure modifiers, some of which are specifically
       designed for use in conjunction with the test script and data
       files that are distributed as part of PCRE2. All the modifiers
       are documented here, some without much justification, but many of
       them are unlikely to be of use except when testing the libraries.

PCRE2's 8-BIT, 16-BIT AND 32-BIT LIBRARIES         top

       Different versions of the PCRE2 library can be built to support
       character strings that are encoded in 8-bit, 16-bit, or 32-bit
       code units. One, two, or all three of these libraries may be
       simultaneously installed. The pcre2test program can be used to
       test all the libraries. However, its own input and output are
       always in 8-bit format. When testing the 16-bit or 32-bit
       libraries, patterns and subject strings are converted to 16-bit
       or 32-bit format before being passed to the library functions.
       Results are converted back to 8-bit code units for output.

       In the rest of this document, the names of library functions and
       structures are given in generic form, for example,
       pcre2_compile(). The actual names used in the libraries have a
       suffix _8, _16, or _32, as appropriate.

INPUT ENCODING         top

       Input to pcre2test is processed line by line, either by calling
       the C library's fgets() function, or via the libreadline or
       libedit library. In some Windows environments character 26 (hex
       1A) causes an immediate end of file, and no further data is read,
       so this character should be avoided unless you really want that

       The input is processed using using C's string functions, so must
       not contain binary zeros, even though in Unix-like environments,
       fgets() treats any bytes other than newline as data characters.
       An error is generated if a binary zero is encountered. By default
       subject lines are processed for backslash escapes, which makes it
       possible to include any data value in strings that are passed to
       the library for matching. For patterns, there is a facility for
       specifying some or all of the 8-bit input characters as
       hexadecimal pairs, which makes it possible to include binary

   Input for the 16-bit and 32-bit libraries

       When testing the 16-bit or 32-bit libraries, there is a need to
       be able to generate character code points greater than 255 in the
       strings that are passed to the library. For subject lines,
       backslash escapes can be used. In addition, when the utf modifier
       (see "Setting compilation options" below) is set, the pattern and
       any following subject lines are interpreted as UTF-8 strings and
       translated to UTF-16 or UTF-32 as appropriate.

       For non-UTF testing of wide characters, the utf8_input modifier
       can be used. This is mutually exclusive with utf, and is allowed
       only in 16-bit or 32-bit mode. It causes the pattern and
       following subject lines to be treated as UTF-8 according to the
       original definition (RFC 2279), which allows for character values
       up to 0x7fffffff. Each character is placed in one 16-bit or
       32-bit code unit (in the 16-bit case, values greater than 0xffff
       cause an error to occur).

       UTF-8 (in its original definition) is not capable of encoding
       values greater than 0x7fffffff, but such values can be handled by
       the 32-bit library. When testing this library in non-UTF mode
       with utf8_input set, if any character is preceded by the byte
       0xff (which is an invalid byte in UTF-8) 0x80000000 is added to
       the character's value. This is the only way of passing such code
       points in a pattern string. For subject strings, using an escape
       sequence is preferable.


       -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 the 8-bit library has not 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 no other library has been built, this is
              the default. If the 32-bit library has not been built,
              this option causes an error.

       -ac    Behave as if each pattern has the auto_callout modifier,
              that is, insert automatic callouts into every pattern that
              is compiled.

       -AC    As for -ac, but in addition behave as if each subject line
              has the callout_extra modifier, that is, show additional
              information from callouts.

       -b     Behave as if each pattern has the fullbincode modifier;
              the full internal binary form of the pattern is output
              after compilation.

       -C     Output the version number of the PCRE2 library, and all
              available information about the optional features that are
              included, and then exit with zero exit code. All other
              options are ignored. If both -C and -LM are present,
              whichever is first is recognized.

       -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
                             exit code is set to the link size
                newline    the default newline setting:
                             CR, LF, CRLF, ANYCRLF, ANY, or NUL
                             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:

                backslash-C  \C is supported (not locked out)
                ebcdic       compiled for an EBCDIC environment
                jit          just-in-time support is available
                pcre2-16     the 16-bit library was built
                pcre2-32     the 32-bit library was built
                pcre2-8      the 8-bit library was built
                unicode      Unicode 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 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 subject line has the dfa modifier;
              matching is done using the pcre2_dfa_match() function
              instead of the default pcre2_match().

       -error number[,number,...]
              Call pcre2_get_error_message() for each of the error
              numbers in the comma-separated list, display the resulting
              messages on the standard output, then exit with zero exit
              code. The numbers may be positive or negative. This is a
              convenience facility for PCRE2 maintainers.

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

       -i     Behave as if each pattern has the info modifier;
              information about the compiled pattern is given after

       -jit   Behave as if each pattern line has the jit modifier; after
              successful compilation, each pattern is passed to the
              just-in-time compiler, if available.

              Behave as if each pattern line has the jitfast modifier;
              after successful compilation, each pattern is passed to
              the just-in-time compiler, if available, and each subject
              line is passed directly to the JIT matcher via its "fast

              Behave as if each pattern line has the jitverify modifier;
              after successful compilation, each pattern is passed to
              the just-in-time compiler, if available, and the use of
              JIT for matching is verified.

       -LM    List modifiers: write a list of available pattern and
              subject modifiers to the standard output, then exit with
              zero exit code. All other options are ignored.  If both -C
              and any -Lx options are present, whichever is first is

       -LP    List properties: write a list of recognized Unicode
              properties to the standard output, then exit with zero
              exit code. All other options are ignored. If both -C and
              any -Lx options are present, whichever is first is

       -LS    List scripts: write a list of recognized Unicode script
              names to the standard output, then exit with zero exit
              code. All other options are ignored. If both -C and any
              -Lx options are present, whichever is first is recognized.

       -pattern modifier-list
              Behave as if each pattern line contains the given

       -q     Do not output the version number of pcre2test at the start
              of execution.

       -S size
              On Unix-like systems, set the size of the run-time stack
              to size mebibytes (units of 1024*1024 bytes).

       -subject modifier-list
              Behave as if each subject line contains the given

       -t     Run each compile and match many times with a timer, and
              output the resulting times per compile or match. When JIT
              is used, separate times are given for the initial compile
              and the JIT compile. 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 500,000 times.

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

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

              Output the PCRE2 version number and then exit.

DESCRIPTION         top

       If pcre2test is given two filename arguments, it reads from the
       first and writes to the second. If the first name is "-", input
       is taken from the standard input. If pcre2test is given only one
       argument, it reads from that file and writes to stdout.
       Otherwise, it reads from stdin and writes to stdout.

       When pcre2test is built, a configuration option can specify that
       it should be linked with the libreadline or libedit 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 tests, each of which consists
       of a set of input lines. Each set starts with a regular
       expression pattern, followed by any number of subject lines to be
       matched against that pattern. In between sets of test data,
       command lines that begin with # may appear. This file format,
       with some restrictions, can also be processed by the perltest.sh
       script that is distributed with PCRE2 as a means of checking that
       the behaviour of PCRE2 and Perl is the same. For a specification
       of perltest.sh, see the comments near its beginning. See also the
       #perltest command below.

       When the input is a terminal, pcre2test prompts for each line of
       input, using "re>" to prompt for regular expression patterns, and
       "data>" to prompt for subject lines. Command lines starting with
       # can be entered only in response to the "re>" prompt.

       Each subject 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 subject lines; the input buffer is
       automatically extended if it is too small. There are replication
       features that makes it possible to generate long repetitive
       pattern or subject lines without having to supply them

       An empty line or the end of the file signals the end of the
       subject lines for a test, at which point a new pattern or command
       line is expected if there is still input to be read.

COMMAND LINES         top

       In between sets of test data, a line that begins with # is
       interpreted as a command line. If the first character is followed
       by white space or an exclamation mark, the line is treated as a
       comment, and ignored. Otherwise, the following commands are


       Subsequent patterns automatically have the PCRE2_NEVER_UTF and
       PCRE2_NEVER_UCP options set, which locks out the use of the
       PCRE2_UTF and PCRE2_UCP options and the use of (*UTF) and (*UCP)
       at the start of patterns. This command also forces an error if a
       subsequent pattern contains any occurrences of \P, \p, or \X,
       which are still supported when PCRE2_UTF is not set, but which
       require Unicode property support to be included in the library.

       This is a trigger guard that is used in test files to ensure that
       UTF or Unicode property tests are not accidentally added to files
       that are used when Unicode support is not included in the
       library. Setting PCRE2_NEVER_UTF and PCRE2_NEVER_UCP as a default
       can also be obtained by the use of #pattern; the difference is
       that #forbid_utf cannot be unset, and the automatic options are
       not displayed in pattern information, to avoid cluttering up test

         #load <filename>

       This command is used to load a set of precompiled patterns from a
       file, as described in the section entitled "Saving and restoring
       compiled patterns" below.

         #loadtables <filename>

       This command is used to load a set of binary character tables
       that can be accessed by the tables=3 qualifier. Such tables can
       be created by the pcre2_dftables program with the -b option.

         #newline_default [<newline-list>]

       When PCRE2 is built, a default newline convention can be
       specified. This determines which characters and/or character
       pairs are recognized as indicating a newline in a pattern or
       subject string. The default can be overridden when a pattern is
       compiled. The standard test files contain tests of various
       newline conventions, but the majority of the tests expect a
       single linefeed to be recognized as a newline by default. Without
       special action the tests would fail when PCRE2 is compiled with
       either CR or CRLF as the default newline.

       The #newline_default command specifies a list of newline types
       that are acceptable as the default. The types must be one of CR,
       LF, CRLF, ANYCRLF, ANY, or NUL (in upper or lower case), for

         #newline_default LF Any anyCRLF

       If the default newline is in the list, this command has no
       effect. Otherwise, except when testing the POSIX API, a newline
       modifier that specifies the first newline convention in the list
       (LF in the above example) is added to any pattern that does not
       already have a newline modifier. If the newline list is empty,
       the feature is turned off. This command is present in a number of
       the standard test input files.

       When the POSIX API is being tested there is no way to override
       the default newline convention, though it is possible to set the
       newline convention from within the pattern. A warning is given if
       the posix or posix_nosub modifier is used when #newline_default
       would set a default for the non-POSIX API.

         #pattern <modifier-list>

       This command sets a default modifier list that applies to all
       subsequent patterns. Modifiers on a pattern can change these


       This line is used in test files that can also be processed by
       perltest.sh to confirm that Perl gives the same results as PCRE2.
       Subsequent tests are checked for the use of pcre2test features
       that are incompatible with the perltest.sh script.

       Patterns must use '/' as their delimiter, and only certain
       modifiers are supported. Comment lines, #pattern commands, and
       #subject commands that set or unset "mark" are recognized and
       acted on. The #perltest, #forbid_utf, and #newline_default
       commands, which are needed in the relevant pcre2test files, are
       silently ignored. All other command lines are ignored, but give a
       warning message. The #perltest command helps detect tests that
       are accidentally put in the wrong file or use the wrong
       delimiter. For more details of the perltest.sh script see the
       comments it contains.

         #pop [<modifiers>]
         #popcopy [<modifiers>]

       These commands are used to manipulate the stack of compiled
       patterns, as described in the section entitled "Saving and
       restoring compiled patterns" below.

         #save <filename>

       This command is used to save a set of compiled patterns to a
       file, as described in the section entitled "Saving and restoring
       compiled patterns" below.

         #subject <modifier-list>

       This command sets a default modifier list that applies to all
       subsequent subject lines. Modifiers on a subject line can change
       these settings.


       Modifier lists are used with both pattern and subject lines.
       Items in a list are separated by commas followed by optional
       white space. Trailing whitespace in a modifier list is ignored.
       Some modifiers may be given for both patterns and subject lines,
       whereas others are valid only for one or the other. Each modifier
       has a long name, for example "anchored", and some of them must be
       followed by an equals sign and a value, for example, "offset=12".
       Values cannot contain comma characters, but may contain spaces.
       Modifiers that do not take values may be preceded by a minus sign
       to turn off a previous setting.

       A few of the more common modifiers can also be specified as
       single letters, for example "i" for "caseless". In documentation,
       following the Perl convention, these are written with a slash
       ("the /i modifier") for clarity. Abbreviated modifiers must all
       be concatenated in the first item of a modifier list. If the
       first item is not recognized as a long modifier name, it is
       interpreted as a sequence of these abbreviations. For example:


       This is a pattern line whose modifier list starts with two one-
       letter modifiers (/i and /g). The lower-case abbreviated
       modifiers are the same as used in Perl.

PATTERN SYNTAX         top

       A pattern line must start with one of the following characters
       (common symbols, excluding pattern meta-characters):

         / ! " ' ` - = _ : ; , % & @ ~

       This is interpreted as the pattern's delimiter. 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 as a literal within the pattern
       by escaping it with a backslash, for example


       If you do this, the escape and the delimiter form part of the
       pattern, but since the delimiters are all non-alphanumeric, the
       inclusion of the backslash does not affect the pattern's
       interpretation. Note, however, that this trick does not work
       within \Q...\E literal bracketing because the backslash will
       itself be interpreted as a literal. If the terminating delimiter
       is immediately followed by a backslash, for example,


       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 pcre2test to read the next line as a continuation
       of the regular expression.

       A pattern can be followed by a modifier list (details below).


       Before each subject line is passed to pcre2_match(),
       pcre2_dfa_match(), or pcre2_jit_match(), leading and trailing
       white space is removed, and the line is scanned for backslash
       escapes, unless the subject_literal modifier was set for the
       pattern. The following provide a means of encoding non-printing
       characters in a visible way:

         \a         alarm (BEL, \x07)
         \b         backspace (\x08)
         \e         escape (\x27)
         \f         form feed (\x0c)
         \n         newline (\x0a)
         \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
         \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)

       The use of \x{hh...} is not dependent on the use of the utf
       modifier on the pattern. It is recognized always. There may be
       any number of hexadecimal digits inside the braces; invalid
       values provoke error messages.

       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 purposes.

       There is a special backslash sequence that specifies replication
       of one or more characters:


       This makes it possible to test long strings without having to
       provide them as part of the file. For example:


       is converted to "abcabcabcabc". This feature does not support
       nesting. To include a closing square bracket in the characters,
       code it as \x5D.

       A backslash followed by an equals sign marks the end of the
       subject string and the start of a modifier list. For example:


       If the subject string is empty and \= is followed by whitespace,
       the line is treated as a comment line, and is not used for
       matching. For example:

         \= This is a comment.
         abc\= This is an invalid modifier list.

       A backslash followed by any other non-alphanumeric character just
       escapes that character. A backslash followed by anything else
       causes an error. However, if the very last character in the line
       is a backslash (and there is no modifier list), it is ignored.
       This gives a way of passing an empty line as data, since a real
       empty line terminates the data input.

       If the subject_literal modifier is set for a pattern, all subject
       lines that follow are treated as literals, with no special
       treatment of backslashes.  No replication is possible, and any
       subject modifiers must be set as defaults by a #subject command.


       There are several types of modifier that can appear in pattern
       lines. Except where noted below, they may also be used in
       #pattern commands. A pattern's modifier list can add to or
       override default modifiers that were set by a previous #pattern

   Setting compilation options

       The following modifiers set options for pcre2_compile(). Most of
       them set bits in the options argument of that function, but those
       whose names start with PCRE2_EXTRA are additional options that
       are set in the compile context.  Some of these options have
       single-letter abbreviations. There is special handling for /x: if
       a second x is present, PCRE2_EXTENDED is converted into
       PCRE2_EXTENDED_MORE as in Perl. A third appearance adds
       PCRE2_EXTENDED as well, though this makes no difference to the
       way pcre2_compile() behaves. See pcre2api for a description of
       the effects of these options.

             allow_empty_class         set PCRE2_ALLOW_EMPTY_CLASS
             allow_lookaround_bsk      set
             allow_surrogate_escapes   set
             alt_bsux                  set PCRE2_ALT_BSUX
             alt_circumflex            set PCRE2_ALT_CIRCUMFLEX
             alt_verbnames             set PCRE2_ALT_VERBNAMES
             anchored                  set PCRE2_ANCHORED
         /a  ascii_all                 set all ASCII options
             ascii_bsd                 set PCRE2_EXTRA_ASCII_BSD
             ascii_bss                 set PCRE2_EXTRA_ASCII_BSS
             ascii_bsw                 set PCRE2_EXTRA_ASCII_BSW
             ascii_digit               set PCRE2_EXTRA_ASCII_DIGIT
             ascii_posix               set PCRE2_EXTRA_ASCII_POSIX
             auto_callout              set PCRE2_AUTO_CALLOUT
             bad_escape_is_literal     set
         /i  caseless                  set PCRE2_CASELESS
         /r  caseless_restrict         set PCRE2_EXTRA_CASELESS_RESTRICT
             dollar_endonly            set PCRE2_DOLLAR_ENDONLY
         /s  dotall                    set PCRE2_DOTALL
             dupnames                  set PCRE2_DUPNAMES
             endanchored               set PCRE2_ENDANCHORED
             escaped_cr_is_lf          set PCRE2_EXTRA_ESCAPED_CR_IS_LF
         /x  extended                  set PCRE2_EXTENDED
         /xx extended_more             set PCRE2_EXTENDED_MORE
             extra_alt_bsux            set PCRE2_EXTRA_ALT_BSUX
             firstline                 set PCRE2_FIRSTLINE
             literal                   set PCRE2_LITERAL
             match_line                set PCRE2_EXTRA_MATCH_LINE
             match_invalid_utf         set PCRE2_MATCH_INVALID_UTF
             match_unset_backref       set PCRE2_MATCH_UNSET_BACKREF
             match_word                set PCRE2_EXTRA_MATCH_WORD
         /m  multiline                 set PCRE2_MULTILINE
             never_backslash_c         set PCRE2_NEVER_BACKSLASH_C
             never_ucp                 set PCRE2_NEVER_UCP
             never_utf                 set PCRE2_NEVER_UTF
         /n  no_auto_capture           set PCRE2_NO_AUTO_CAPTURE
             no_auto_possess           set PCRE2_NO_AUTO_POSSESS
             no_dotstar_anchor         set PCRE2_NO_DOTSTAR_ANCHOR
             no_start_optimize         set PCRE2_NO_START_OPTIMIZE
             no_utf_check              set PCRE2_NO_UTF_CHECK
             ucp                       set PCRE2_UCP
             ungreedy                  set PCRE2_UNGREEDY
             use_offset_limit          set PCRE2_USE_OFFSET_LIMIT
             utf                       set PCRE2_UTF

       As well as turning on the PCRE2_UTF option, the utf 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. Setting utf
       in 16-bit or 32-bit mode also causes pattern and subject strings
       to be translated to UTF-16 or UTF-32, respectively, before being
       passed to library functions.

   Setting compilation controls

       The following modifiers affect the compilation process or request
       information about the pattern. There are single-letter
       abbreviations for some that are heavily used in the test files.

             bsr=[anycrlf|unicode]     specify \R handling
         /B  bincode                   show binary code without lengths
             callout_info              show callout information
             convert=<options>         request foreign pattern
             convert_glob_escape=c     set glob escape character
             convert_glob_separator=c  set glob separator character
             convert_length            set convert buffer length
             debug                     same as info,fullbincode
             framesize                 show matching frame size
             fullbincode               show binary code with lengths
         /I  info                      show info about compiled pattern
             hex                       unquoted characters are
             jit[=<number>]            use JIT
             jitfast                   use JIT fast path
             jitverify                 verify JIT use
             locale=<name>             use this locale
             max_pattern_length=<n>    set maximum pattern length
             max_varlookbehind=<n>     set maximum variable lookbehind
             memory                    show memory used
             newline=<type>            set newline type
             null_context              compile with a NULL context
             null_pattern              pass pattern as NULL
             parens_nest_limit=<n>     set maximum parentheses depth
             posix                     use the POSIX API
             posix_nosub               use the POSIX API with REG_NOSUB
             push                      push compiled pattern onto the
             pushcopy                  push a copy onto the stack
             stackguard=<number>       test the stackguard feature
             subject_literal           treat all subject lines as
             tables=[0|1|2|3]          select internal tables
             use_length                do not zero-terminate the pattern
             utf8_input                treat input as UTF-8

       The effects of these modifiers are described in the following

   Newline and \R handling

       The bsr modifier specifies what \R in a pattern should match. If
       it is set to "anycrlf", \R matches CR, LF, or CRLF only. If it is
       set to "unicode", \R matches any Unicode newline sequence. The
       default can be specified when PCRE2 is built; if it is not, the
       default is set to Unicode.

       The newline modifier specifies which characters are to be
       interpreted as newlines, both in the pattern and in subject
       lines. The type must be one of CR, LF, CRLF, ANYCRLF, ANY, or NUL
       (in upper or lower case).

   Information about a pattern

       The debug modifier is a shorthand for info,fullbincode,
       requesting all available information.

       The bincode modifier causes a representation of the compiled code
       to be output after compilation. This information does not contain
       length and offset values, which ensures that the same output is
       generated for different internal link sizes and different code
       unit widths. By using bincode, the same regression tests can be
       used in different environments.

       The fullbincode modifier, by contrast, does include length and
       offset values. This is used in a few special tests that run only
       for specific code unit widths and link sizes, and is also useful
       for one-off tests.

       The info modifier requests information about the compiled pattern
       (whether it is anchored, has a fixed first character, and so on).
       The information is obtained from the pcre2_pattern_info()
       function. Here are some typical examples:

           re> /(?i)(^a|^b)/m,info
         Capture group count = 1
         Compile options: multiline
         Overall options: caseless multiline
         First code unit at start or follows newline
         Subject length lower bound = 1

           re> /(?i)abc/info
         Capture group count = 0
         Compile options: <none>
         Overall options: caseless
         First code unit = 'a' (caseless)
         Last code unit = 'c' (caseless)
         Subject length lower bound = 3

       "Compile options" are those specified by modifiers; "overall
       options" have added options that are taken or deduced from the
       pattern. If both sets of options are the same, just a single
       "options" line is output; if there are no options, the line is
       omitted. "First code unit" is where any match must start; if
       there is more than one they are listed as "starting code units".
       "Last code unit" is the last literal code unit that must be
       present in any match. This is not necessarily the last character.
       These lines are omitted if no starting or ending code units are
       recorded. The subject length line is omitted when
       no_start_optimize is set because the minimum length is not
       calculated when it can never be used.

       The framesize modifier shows the size, in bytes, of each storage
       frame used by pcre2_match() for handling backtracking. The size
       depends on the number of capturing parentheses in the pattern. A
       vector of these frames is used at matching time; its overall size
       is shown when the heaframes_size subject modifier is set.

       The callout_info modifier requests information about all the
       callouts in the pattern. A list of them is output at the end of
       any other information that is requested. For each callout, either
       its number or string is given, followed by the item that follows
       it in the pattern.

   Passing a NULL context

       Normally, pcre2test passes a context block to pcre2_compile(). If
       the null_context modifier is set, however, NULL is passed. This
       is for testing that pcre2_compile() behaves correctly in this
       case (it uses default values).

   Passing a NULL pattern

       The null_pattern modifier is for testing the behaviour of
       pcre2_compile() when the pattern argument is NULL. The length
       value passed is the default PCRE2_ZERO_TERMINATED unless
       use_length is set.  Any length other than zero causes an error.

   Specifying pattern characters in hexadecimal

       The hex modifier specifies that the characters of the pattern,
       except for substrings enclosed in single or double quotes, are to
       be interpreted as pairs of hexadecimal digits. This feature is
       provided as a way of creating patterns that contain binary zeros
       and other non-printing characters. White space is permitted
       between pairs of digits. For example, this pattern contains three

         /ab 32 59/hex

       Parts of such a pattern are taken literally if quoted. This
       pattern contains nine characters, only two of which are specified
       in hexadecimal:

         /ab "literal" 32/hex

       Either single or double quotes may be used. There is no way of
       including the delimiter within a substring. The hex and expand
       modifiers are mutually exclusive.

   Specifying the pattern's length

       By default, patterns are passed to the compiling functions as
       zero-terminated strings but can be passed by length instead of
       being zero-terminated. The use_length modifier causes this to
       happen. Using a length happens automatically (whether or not
       use_length is set) when hex is set, because patterns specified in
       hexadecimal may contain binary zeros.

       If hex or use_length is used with the POSIX wrapper API (see
       "Using the POSIX wrapper API" below), the REG_PEND extension is
       used to pass the pattern's length.

   Specifying a maximum for variable lookbehinds

       Variable lookbehind assertions are supported only if, for each
       one, there is a maximum length (in characters) that it can match.
       There is a limit on this, whose default can be set at build time,
       with an ultimate default of 255. The max_varlookbehind modifier
       uses the pcre2_set_max_varlookbehind() function to change the
       limit. Lookbehinds whose branches each match a fixed length are
       limited to 65535 characters per branch.

   Specifying wide characters in 16-bit and 32-bit modes

       In 16-bit and 32-bit modes, all input is automatically treated as
       UTF-8 and translated to UTF-16 or UTF-32 when the utf modifier is
       set. For testing the 16-bit and 32-bit libraries in non-UTF mode,
       the utf8_input modifier can be used. It is mutually exclusive
       with utf. Input lines are interpreted as UTF-8 as a means of
       specifying wide characters. More details are given in "Input
       encoding" above.

   Generating long repetitive patterns

       Some tests use long patterns that are very repetitive. Instead of
       creating a very long input line for such a pattern, you can use a
       special repetition feature, similar to the one described for
       subject lines above. If the expand modifier is present on a
       pattern, parts of the pattern that have the form


       are expanded before the pattern is passed to pcre2_compile(). For
       example, \[AB]{6000} is expanded to "ABAB..." 6000 times. This
       construction cannot be nested. An initial "\[" sequence is
       recognized only if "]{" followed by decimal digits and "}" is
       found later in the pattern. If not, the characters remain in the
       pattern unaltered. The expand and hex modifiers are mutually

       If part of an expanded pattern looks like an expansion, but is
       really part of the actual pattern, unwanted expansion can be
       avoided by giving two values in the quantifier. For example,
       \[AB]{6000,6000} is not recognized as an expansion item.

       If the info modifier is set on an expanded pattern, the result of
       the expansion is included in the information that is output.

   JIT compilation

       Just-in-time (JIT) compiling is a heavyweight optimization that
       can greatly speed up pattern matching. See the pcre2jit
       documentation for details. JIT compiling happens, optionally,
       after a pattern has been successfully compiled into an internal
       form. The JIT compiler converts this to optimized machine code.
       It needs to know whether the match-time options
       PCRE2_PARTIAL_HARD and PCRE2_PARTIAL_SOFT are going to be used,
       because different code is generated for the different cases. See
       the partial modifier in "Subject Modifiers" below for details of
       how these options are specified for each match attempt.

       JIT compilation is requested by the jit pattern modifier, which
       may optionally be followed by an equals sign and a number in the
       range 0 to 7.  The three bits that make up the number specify
       which of the three JIT operating modes are to be compiled:

         1  compile JIT code for non-partial matching
         2  compile JIT code for soft partial matching
         4  compile JIT code for hard partial matching

       The possible values for the jit modifier are therefore:

         0  disable JIT
         1  normal matching only
         2  soft partial matching only
         3  normal and soft partial matching
         4  hard partial matching only
         6  soft and hard partial matching only
         7  all three modes

       If no number is given, 7 is assumed. The phrase "partial
       matching" means a call to pcre2_match() with either the
       PCRE2_PARTIAL_SOFT or the PCRE2_PARTIAL_HARD option set. Note
       that such a call may return a complete match; the options enable
       the possibility of a partial match, but do not require it. Note
       also that if you request JIT compilation only for partial
       matching (for example, jit=2) but do not set the partial modifier
       on a subject line, that match will not use JIT code because none
       was compiled for non-partial matching.

       If JIT compilation is successful, the compiled JIT code will
       automatically be used when an appropriate type of match is run,
       except when incompatible run-time options are specified. For more
       details, see the pcre2jit documentation. See also the jitstack
       modifier below for a way of setting the size of the JIT stack.

       If the jitfast modifier is specified, matching is done using the
       JIT "fast path" interface, pcre2_jit_match(), which skips some of
       the sanity checks that are done by pcre2_match(), and of course
       does not work when JIT is not supported. If jitfast is specified
       without jit, jit=7 is assumed.

       If the jitverify modifier is specified, information about the
       compiled pattern shows whether JIT compilation was or was not
       successful. If jitverify is specified without jit, jit=7 is
       assumed. If JIT compilation is successful when jitverify is set,
       the text "(JIT)" is added to the first output line after a match
       or non match when JIT-compiled code was actually used in the

   Setting a locale

       The locale modifier must specify the name of a locale, for


       The given locale is set, pcre2_maketables() is called to build a
       set of character tables for the locale, and this is then passed
       to pcre2_compile() when compiling the regular expression. The
       same tables are used when matching the following subject lines.
       The locale modifier applies only to the pattern on which it
       appears, but can be given in a #pattern command if a default is
       needed. Setting a locale and alternate character tables are
       mutually exclusive.

   Showing pattern memory

       The memory modifier causes the size in bytes of the memory used
       to hold the compiled pattern to be output. This does not include
       the size of the pcre2_code block; it is just the actual compiled
       data. If the pattern is subsequently passed to the JIT compiler,
       the size of the JIT compiled code is also output. Here is an

           re> /a(b)c/jit,memory
         Memory allocation (code space): 21
         Memory allocation (JIT code): 1910

   Limiting nested parentheses

       The parens_nest_limit modifier sets a limit on the depth of
       nested parentheses in a pattern. Breaching the limit causes a
       compilation error.  The default for the library is set when PCRE2
       is built, but pcre2test sets its own default of 220, which is
       required for running the standard test suite.

   Limiting the pattern length

       The max_pattern_length modifier sets a limit, in code units, to
       the length of pattern that pcre2_compile() will accept. Breaching
       the limit causes a compilation error. The default is the largest
       number a PCRE2_SIZE variable can hold (essentially unlimited).

   Using the POSIX wrapper API

       The posix and posix_nosub modifiers cause pcre2test to call PCRE2
       via the POSIX wrapper API rather than its native API. When
       posix_nosub is used, the POSIX option REG_NOSUB is passed to
       regcomp(). The POSIX wrapper supports only the 8-bit library.
       Note that it does not imply POSIX matching semantics; for more
       detail see the pcre2posix documentation. The following pattern
       modifiers set options for the regcomp() function:

         caseless           REG_ICASE
         multiline          REG_NEWLINE
         dotall             REG_DOTALL     )
         ungreedy           REG_UNGREEDY   ) These options are not part
         ucp                REG_UCP        )   the POSIX standard
         utf                REG_UTF8       )

       The regerror_buffsize modifier specifies a size for the error
       buffer that is passed to regerror() in the event of a compilation
       error. For example:


       This provides a means of testing the behaviour of regerror() when
       the buffer is too small for the error message. If this modifier
       has not been set, a large buffer is used.

       The aftertext and allaftertext subject modifiers work as
       described below. All other modifiers are either ignored, with a
       warning message, or cause an error.

       The pattern is passed to regcomp() as a zero-terminated string by
       default, but if the use_length or hex modifiers are set, the
       REG_PEND extension is used to pass it by length.

   Testing the stack guard feature

       The stackguard modifier is used to test the use of
       pcre2_set_compile_recursion_guard(), a function that is provided
       to enable stack availability to be checked during compilation
       (see the pcre2api documentation for details). If the number
       specified by the modifier is greater than zero,
       pcre2_set_compile_recursion_guard() is called to set up callback
       from pcre2_compile() to a local function. The argument it
       receives is the current nesting parenthesis depth; if this is
       greater than the value given by the modifier, non-zero is
       returned, causing the compilation to be aborted.

   Using alternative character tables

       The value specified for the tables modifier must be one of the
       digits 0, 1, 2, or 3. It causes a specific set of built-in
       character tables to be passed to pcre2_compile(). This is used in
       the PCRE2 tests to check behaviour with different character
       tables. The digit specifies the tables as follows:

         0   do not pass any special character tables
         1   the default ASCII tables, as distributed in
         2   a set of tables defining ISO 8859 characters
         3   a set of tables loaded by the #loadtables command

       In tables 2, some characters whose codes are greater than 128 are
       identified as letters, digits, spaces, etc. Tables 3 can be used
       only after a #loadtables command has loaded them from a binary
       file. Setting alternate character tables and a locale are
       mutually exclusive.

   Setting certain match controls

       The following modifiers are really subject modifiers, and are
       described under "Subject Modifiers" below. However, they may be
       included in a pattern's modifier list, in which case they are
       applied to every subject line that is processed with that
       pattern. These modifiers do not affect the compilation process.

             aftertext                   show text after match
             allaftertext                show text after captures
             allcaptures                 show all captures
             allvector                   show the entire ovector
             allusedtext                 show all consulted text
             altglobal                   alternative global matching
         /g  global                      global matching
             heapframes_size             show match data heapframes size
             jitstack=<n>                set size of JIT stack
             mark                        show mark values
             replace=<string>            specify a replacement string
             startchar                   show starting character when
             substitute_callout          use substitution callouts
             substitute_extended         use PCRE2_SUBSTITUTE_EXTENDED
             substitute_literal          use PCRE2_SUBSTITUTE_LITERAL
             substitute_matched          use PCRE2_SUBSTITUTE_MATCHED
             substitute_overflow_length  use
             substitute_replacement_only use
             substitute_skip=<n>         skip substitution <n>
             substitute_stop=<n>         skip substitution <n> and
             substitute_unknown_unset    use
             substitute_unset_empty      use

       These modifiers may not appear in a #pattern command. If you want
       them as defaults, set them in a #subject command.

   Specifying literal subject lines

       If the subject_literal modifier is present on a pattern, all the
       subject lines that it matches are taken as literal strings, with
       no interpretation of backslashes. It is not possible to set
       subject modifiers on such lines, but any that are set as defaults
       by a #subject command are recognized.

   Saving a compiled pattern

       When a pattern with the push modifier is successfully compiled,
       it is pushed onto a stack of compiled patterns, and pcre2test
       expects the next line to contain a new pattern (or a command)
       instead of a subject line. This facility is used when saving
       compiled patterns to a file, as described in the section entitled
       "Saving and restoring compiled patterns" below.  If pushcopy is
       used instead of push, a copy of the compiled pattern is stacked,
       leaving the original as current, ready to match the following
       input lines. This provides a way of testing the pcre2_code_copy()
       function.  The push and pushcopy  modifiers are incompatible with
       compilation modifiers such as global that act at match time. Any
       that are specified are ignored (for the stacked copy), with a
       warning message, except for replace, which causes an error. Note
       that jitverify, which is allowed, does not carry through to any
       subsequent matching that uses a stacked pattern.

   Testing foreign pattern conversion

       The experimental foreign pattern conversion functions in PCRE2
       can be tested by setting the convert modifier. Its argument is a
       colon-separated list of options, which set the equivalent option
       for the pcre2_pattern_convert() function:

         glob                    PCRE2_CONVERT_GLOB
         glob_no_starstar        PCRE2_CONVERT_GLOB_NO_STARSTAR
         glob_no_wild_separator  PCRE2_CONVERT_GLOB_NO_WILD_SEPARATOR
         posix_basic             PCRE2_CONVERT_POSIX_BASIC
         posix_extended          PCRE2_CONVERT_POSIX_EXTENDED
         unset                   Unset all options

       The "unset" value is useful for turning off a default that has
       been set by a #pattern command. When one of these options is set,
       the input pattern is passed to pcre2_pattern_convert(). If the
       conversion is successful, the result is reflected in the output
       and then passed to pcre2_compile(). The normal utf and
       no_utf_check options, if set, cause the PCRE2_CONVERT_UTF and
       PCRE2_CONVERT_NO_UTF_CHECK options to be passed to

       By default, the conversion function is allowed to allocate a
       buffer for its output. However, if the convert_length modifier is
       set to a value greater than zero, pcre2test passes a buffer of
       the given length. This makes it possible to test the length

       The convert_glob_escape and convert_glob_separator modifiers can
       be used to specify the escape and separator characters for glob
       processing, overriding the defaults, which are operating-system


       The modifiers that can appear in subject lines and the #subject
       command are of two types.

   Setting match options

       The following modifiers set options for pcre2_match() or
       pcre2_dfa_match(). See pcreapi for a description of their

             anchored                  set PCRE2_ANCHORED
             endanchored               set PCRE2_ENDANCHORED
             dfa_restart               set PCRE2_DFA_RESTART
             dfa_shortest              set PCRE2_DFA_SHORTEST
             no_jit                    set PCRE2_NO_JIT
             no_utf_check              set PCRE2_NO_UTF_CHECK
             notbol                    set PCRE2_NOTBOL
             notempty                  set PCRE2_NOTEMPTY
             notempty_atstart          set PCRE2_NOTEMPTY_ATSTART
             noteol                    set PCRE2_NOTEOL
             partial_hard (or ph)      set PCRE2_PARTIAL_HARD
             partial_soft (or ps)      set PCRE2_PARTIAL_SOFT

       The partial matching modifiers are provided with abbreviations
       because they appear frequently in tests.

       If the posix or posix_nosub modifier was present on the pattern,
       causing the POSIX wrapper API to be used, the only option-setting
       modifiers that have any effect are notbol, notempty, and noteol,
       causing REG_NOTBOL, REG_NOTEMPTY, and REG_NOTEOL, respectively,
       to be passed to regexec(). The other modifiers are ignored, with
       a warning message.

       There is one additional modifier that can be used with the POSIX
       wrapper. It is ignored (with a warning) if used for non-POSIX


       This causes the subject string to be passed to regexec() using
       the REG_STARTEND option, which uses offsets to specify which part
       of the string is searched. If only one number is given, the end
       offset is passed as the end of the subject string. For more
       detail of REG_STARTEND, see the pcre2posix documentation. If the
       subject string contains binary zeros (coded as escapes such as
       \x{00} because pcre2test does not support actual binary zeros in
       its input), you must use posix_startend to specify its length.

   Setting match controls

       The following modifiers affect the matching process or request
       additional information. Some of them may also be specified on a
       pattern line (see above), in which case they apply to every
       subject line that is matched against that pattern, but can be
       overridden by modifiers on the subject.

             aftertext                  show text after match
             allaftertext               show text after captures
             allcaptures                show all captures
             allvector                  show the entire ovector
             allusedtext                show all consulted text (non-JIT
             altglobal                  alternative global matching
             callout_capture            show captures at callout time
             callout_data=<n>           set a value to pass via callouts
             callout_error=<n>[:<m>]    control callout error
             callout_extra              show extra callout information
             callout_fail=<n>[:<m>]     control callout failure
             callout_no_where           do not show position of a
             callout_none               do not supply a callout function
             copy=<number or name>      copy captured substring
             depth_limit=<n>            set a depth limit
             dfa                        use pcre2_dfa_match()
             find_limits                find heap, match and depth
             find_limits_noheap         find match and depth limits
             get=<number or name>       extract captured substring
             getall                     extract all captured substrings
         /g  global                     global matching
             heapframes_size            show match data heapframes size
             heap_limit=<n>             set a limit on heap memory
             jitstack=<n>               set size of JIT stack
             mark                       show mark values
             match_limit=<n>            set a match limit
             memory                     show heap memory usage
             null_context               match with a NULL context
             null_replacement           substitute with NULL replacement
             null_subject               match with NULL subject
             offset=<n>                 set starting offset
             offset_limit=<n>           set offset limit
             ovector=<n>                set size of output vector
             recursion_limit=<n>        obsolete synonym for depth_limit
             replace=<string>           specify a replacement string
             startchar                  show startchar when relevant
             startoffset=<n>            same as offset=<n>
             substitute_callout         use substitution callouts
             substitute_extedded        use PCRE2_SUBSTITUTE_EXTENDED
             substitute_literal         use PCRE2_SUBSTITUTE_LITERAL
             substitute_matched         use PCRE2_SUBSTITUTE_MATCHED
             substitute_overflow_length use
             substitute_replacement_only use
             substitute_skip=<n>        skip substitution number n
             substitute_stop=<n>        skip substitution number n and
             substitute_unknown_unset   use
             substitute_unset_empty     use PCRE2_SUBSTITUTE_UNSET_EMPTY
             zero_terminate             pass the subject as zero-

       The effects of these modifiers are described in the following
       sections. When matching via the POSIX wrapper API, the aftertext,
       allaftertext, and ovector subject modifiers work as described
       below. All other modifiers are either ignored, with a warning
       message, or cause an error.

   Showing more text

       The aftertext modifier requests that as well as outputting the
       part of the subject string that matched the entire pattern,
       pcre2test should in addition output the remainder of the subject
       string. This is useful for tests where the subject contains
       multiple copies of the same substring. The allaftertext modifier
       requests the same action for captured substrings as well as the
       main matched substring. In each case the remainder is output on
       the following line with a plus character following the capture

       The allusedtext modifier requests that all the text that was
       consulted during a successful pattern match by the interpreter
       should be shown, for both full and partial matches. This feature
       is not supported for JIT matching, and if requested with JIT it
       is ignored (with a warning message). Setting this modifier
       affects the output if there is a lookbehind at the start of a
       match, or, for a complete match, a lookahead at the end, or if \K
       is used in the pattern. Characters that precede or follow the
       start and end of the actual match are indicated in the output by
       '<' or '>' characters underneath them.  Here is an example:

           re> /(?<=pqr)abc(?=xyz)/
         data> 123pqrabcxyz456\=allusedtext
          0: pqrabcxyz
             <<<   >>>
         data> 123pqrabcxy\=ph,allusedtext
         Partial match: pqrabcxy

       The first, complete match shows that the matched string is "abc",
       with the preceding and following strings "pqr" and "xyz" having
       been consulted during the match (when processing the assertions).
       The partial match can indicate only the preceding string.

       The startchar modifier requests that the starting character for
       the match be indicated, if it is different to the start of the
       matched string. The only time when this occurs is when \K has
       been processed as part of the match. In this situation, the
       output for the matched string is displayed from the starting
       character instead of from the match point, with circumflex
       characters under the earlier characters. For example:

           re> /abc\Kxyz/
         data> abcxyz\=startchar
          0: abcxyz

       Unlike allusedtext, the startchar modifier can be used with JIT.
       However, these two modifiers are mutually exclusive.

   Showing the value of all capture groups

       The allcaptures 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
       pcre2_match()). Groups that did not take part in the match are
       output as "<unset>". This modifier is not relevant for DFA
       matching (which does no capturing) and does not apply when
       replace is specified; it is ignored, with a warning message, if

   Showing the entire ovector, for all outcomes

       The allvector modifier requests that the entire ovector be shown,
       whatever the outcome of the match. Compare allcaptures, which
       shows only up to the maximum number of capture groups for the
       pattern, and then only for a successful complete non-DFA match.
       This modifier, which acts after any match result, and also for
       DFA matching, provides a means of checking that there are no
       unexpected modifications to ovector fields. Before each match
       attempt, the ovector is filled with a special value, and if this
       is found in both elements of a capturing pair, "<unchanged>" is
       output. After a successful match, this applies to all groups
       after the maximum capture group for the pattern. In other cases
       it applies to the entire ovector. After a partial match, the
       first two elements are the only ones that should be set. After a
       DFA match, the amount of ovector that is used depends on the
       number of matches that were found.

   Testing pattern callouts

       A callout function is supplied when pcre2test calls the library
       matching functions, unless callout_none is specified. Its
       behaviour can be controlled by various modifiers listed above
       whose names begin with callout_. Details are given in the section
       entitled "Callouts" below.  Testing callouts from
       pcre2_substitute() is described separately in "Testing the
       substitution function" below.

   Finding all matches in a string

       Searching for all possible matches within a subject can be
       requested by the global or altglobal modifier. After finding a
       match, the matching function is called again to search the
       remainder of the subject. The difference between global and
       altglobal is that the former uses the start_offset argument to
       pcre2_match() or pcre2_dfa_match() to start searching at a new
       point within the entire string (which is what Perl does), whereas
       the latter passes over a shortened subject. This makes a
       difference to the matching process if the pattern begins with a
       lookbehind assertion (including \b or \B).

       If an empty string is matched, the next match is done with the
       PCRE2_NOTEMPTY_ATSTART and PCRE2_ANCHORED flags set, in order to
       search for another, non-empty, match at the same point in the
       subject. If this 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
       characters occurs.

   Testing substring extraction functions

       The copy and get modifiers can be used to test the
       pcre2_substring_copy_xxx() and pcre2_substring_get_xxx()
       functions.  They can be given more than once, and each can
       specify a capture group name or number, for example:


       If the #subject command is used to set default copy and/or get
       lists, these can be unset by specifying a negative number to
       cancel all numbered groups and an empty name to cancel all named

       The getall modifier tests pcre2_substring_list_get(), which
       extracts all captured substrings.

       If the subject line 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
       substring, followed by the name when the extraction was by name.

   Testing the substitution function

       If the replace modifier is set, the pcre2_substitute() function
       is called instead of one of the matching functions (or after one
       call of pcre2_match() in the case of PCRE2_SUBSTITUTE_MATCHED).
       Note that replacement strings cannot contain commas, because a
       comma signifies the end of a modifier. This is not thought to be
       an issue in a test program.

       Specifying a completely empty replacement string disables this
       modifier.  However, it is possible to specify an empty
       replacement by providing a buffer length, as described below, for
       an otherwise empty replacement.

       Unlike subject strings, pcre2test does not process replacement
       strings for escape sequences. In UTF mode, a replacement string
       is checked to see if it is a valid UTF-8 string. If so, it is
       correctly converted to a UTF string of the appropriate code unit
       width. If it is not a valid UTF-8 string, the individual code
       units are copied directly. This provides a means of passing an
       invalid UTF-8 string for testing purposes.

       The following modifiers set options (in additional to the normal
       match options) for pcre2_substitute():

         global                      PCRE2_SUBSTITUTE_GLOBAL
         substitute_extended         PCRE2_SUBSTITUTE_EXTENDED
         substitute_literal          PCRE2_SUBSTITUTE_LITERAL
         substitute_matched          PCRE2_SUBSTITUTE_MATCHED
         substitute_overflow_length  PCRE2_SUBSTITUTE_OVERFLOW_LENGTH
         substitute_replacement_only PCRE2_SUBSTITUTE_REPLACEMENT_ONLY
         substitute_unknown_unset    PCRE2_SUBSTITUTE_UNKNOWN_UNSET
         substitute_unset_empty      PCRE2_SUBSTITUTE_UNSET_EMPTY

       See the pcre2api documentation for details of these options.

       After a successful substitution, the modified string is output,
       preceded by the number of replacements. This may be zero if there
       were no matches. Here is a simple example of a substitution test:

          1: =xxx=abc=
          2: =xxx=xxx=

       Subject and replacement strings should be kept relatively short
       (fewer than 256 characters) for substitution tests, as fixed-size
       buffers are used. To make it easy to test for buffer overflow, if
       the replacement string starts with a number in square brackets,
       that number is passed to pcre2_substitute() as the size of the
       output buffer, with the replacement string starting at the next
       character. Here is an example that tests the edge case:

          1: 123XYZ123
         Failed: error -47: no more memory

       The default action of pcre2_substitute() is to return
       PCRE2_ERROR_NOMEMORY when the output buffer is too small.
       However, if the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set
       (by using the substitute_overflow_length modifier),
       pcre2_substitute() continues to go through the motions of
       matching and substituting (but not doing any callouts), in order
       to compute the size of buffer that is required. When this
       happens, pcre2test shows the required buffer length (which
       includes space for the trailing zero) as part of the error
       message. For example:

         Failed: error -47: no more memory: 10 code units are needed

       A replacement string is ignored with POSIX and DFA matching.
       Specifying partial matching provokes an error return ("bad option
       value") from pcre2_substitute().

   Testing substitute callouts

       If the substitute_callout modifier is set, a substitution callout
       function is set up. The null_context modifier must not be set,
       because the address of the callout function is passed in a match
       context. When the callout function is called (after each
       substitution), details of the the input and output strings are
       output. For example:

          1(1) Old 0 3 "abc" New 0 5 "<abc>"
          2(1) Old 6 9 "abc" New 8 13 "<abc>"
          2: <abc>def<abc>pqr

       The first number on each callout line is the count of matches.
       The parenthesized number is the number of pairs that are set in
       the ovector (that is, one more than the number of capturing
       groups that were set). Then are listed the offsets of the old
       substring, its contents, and the same for the replacement.

       By default, the substitution callout function returns zero, which
       accepts the replacement and causes matching to continue if /g was
       used. Two further modifiers can be used to test other return
       values. If substitute_skip is set to a value greater than zero
       the callout function returns +1 for the match of that number, and
       similarly substitute_stop returns -1. These cause the replacement
       to be rejected, and -1 causes no further matching to take place.
       If either of them are set, substitute_callout is assumed. For

          1(1) Old 0 3 "abc" New 0 5 "<abc> SKIPPED"
          2(1) Old 6 9 "abc" New 6 11 "<abc>"
          2: abcdef<abc>pqr
          1(1) Old 0 3 "abc" New 0 5 "<abc> STOPPED"
          1: abcdefabcpqr

       If both are set for the same number, stop takes precedence. Only
       a single skip or stop is supported, which is sufficient for
       testing that the feature works.

   Setting the JIT stack size

       The jitstack modifier 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. The value is a
       number of kibibytes (units of 1024 bytes). Setting zero reverts
       to the default of 32KiB. Providing a stack that is larger than
       the default is necessary only for very complicated patterns. If
       jitstack is set non-zero on a subject line it overrides any value
       that was set on the pattern.

   Setting heap, match, and depth limits

       The heap_limit, match_limit, and depth_limit modifiers set the
       appropriate limits in the match context. These values are ignored
       when the find_limits or find_limits_noheap modifier is specified.

   Finding minimum limits

       If the find_limits modifier is present on a subject line,
       pcre2test calls the relevant matching function several times,
       setting different values in the match context via
       pcre2_set_heap_limit(), pcre2_set_match_limit(), or
       pcre2_set_depth_limit() until it finds the smallest value for
       each parameter that allows the match to complete without a "limit
       exceeded" error. The match itself may succeed or fail. An
       alternative modifier, find_limits_noheap, omits the heap limit.
       This is used in the standard tests, because the minimum heap
       limit varies between systems. If JIT is being used, only the
       match limit is relevant, and the other two are automatically

       When using this modifier, the pattern should not contain any
       limit settings such as (*LIMIT_MATCH=...) within it. If such a
       setting is present and is lower than the minimum matching value,
       the minimum value cannot be found because pcre2_set_match_limit()
       etc. are only able to reduce the value of an in-pattern limit;
       they cannot increase it.

       For non-DFA matching, the minimum depth_limit number is a measure
       of how much nested backtracking happens (that is, how deeply the
       pattern's tree is searched). In the case of DFA matching,
       depth_limit controls the depth of recursive calls of the internal
       function that is used for handling pattern recursion, lookaround
       assertions, and atomic groups.

       For non-DFA matching, the match_limit number is a measure of the
       amount of backtracking that takes place, and learning the minimum
       value 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. In the case of DFA matching,
       match_limit controls the total number of calls, both recursive
       and non-recursive, to the internal matching function, thus
       controlling the overall amount of computing resource that is

       For both kinds of matching, the heap_limit number, which is in
       kibibytes (units of 1024 bytes), limits the amount of heap memory
       used for matching.

   Showing MARK names

       The mark modifier causes the names from backtracking control
       verbs that are returned from calls to pcre2_match() to be
       displayed. If a mark is returned for a match, non-match, or
       partial match, pcre2test shows it.  For a match, it is on a line
       by itself, tagged with "MK:". Otherwise, it is added to the non-
       match message.

   Showing memory usage

       The memory modifier causes pcre2test to log the sizes of all heap
       memory allocation and freeing calls that occur during a call to
       pcre2_match() or pcre2_dfa_match(). In the latter case, heap
       memory is used only when a match requires more internal workspace
       that the default allocation on the stack, so in many cases there
       will be no output. No heap memory is allocated during matching
       with JIT. For this modifier to work, the null_context modifier
       must not be set on both the pattern and the subject, though it
       can be set on one or the other.

   Showing the heap frame overall vector size

       The heapframes_size modifier is relevant for matches using
       pcre2_match() without JIT. After a match has run (whether
       successful or not) the size, in bytes, of the allocated heap
       frames vector that is left attached to the match data block is
       shown. If the matching action involved several calls to
       pcre2_match() (for example, global matching or for timing) only
       the final value is shown.

       This modifier is ignored, with a warning, for POSIX or DFA
       matching. JIT matching does not use the heap frames vector, so
       the size is always zero, unless there was a previous non-JIT
       match. Note that specifing a size of zero for the output vector
       (see below) causes pcre2test to free its match data block (and
       associated heap frames vector) and allocate a new one.

   Setting a starting offset

       The offset modifier sets an offset in the subject string at which
       matching starts. Its value is a number of code units, not

   Setting an offset limit

       The offset_limit modifier sets a limit for unanchored matches. If
       a match cannot be found starting at or before this offset in the
       subject, a "no match" return is given. The data value is a number
       of code units, not characters. When this modifier is used, the
       use_offset_limit modifier must have been set for the pattern; if
       not, an error is generated.

   Setting the size of the output vector

       The ovector modifier applies only to the subject line in which it
       appears, though of course it can also be used to set a default in
       a #subject command. It specifies the number of pairs of offsets
       that are available for storing matching information. The default
       is 15.

       A value of zero is useful when testing the POSIX API because it
       causes regexec() to be called with a NULL capture vector. When
       not testing the POSIX API, a value of zero is used to cause
       pcre2_match_data_create_from_pattern() to be called, in order to
       create a new match block of exactly the right size for the
       pattern. (It is not possible to create a match block with a zero-
       length ovector; there is always at least one pair of offsets.)
       The old match data block is freed.

   Passing the subject as zero-terminated

       By default, the subject string is passed to a native API matching
       function with its correct length. In order to test the facility
       for passing a zero-terminated string, the zero_terminate modifier
       is provided. It causes the length to be passed as
       PCRE2_ZERO_TERMINATED. When matching via the POSIX interface,
       this modifier is ignored, with a warning.

       When testing pcre2_substitute(), this modifier also has the
       effect of passing the replacement string as zero-terminated.

   Passing a NULL context, subject, or replacement

       Normally, pcre2test passes a context block to pcre2_match(),
       pcre2_dfa_match(), pcre2_jit_match() or pcre2_substitute().  If
       the null_context modifier is set, however, NULL is passed. This
       is for testing that the matching and substitution functions
       behave correctly in this case (they use default values). This
       modifier cannot be used with the find_limits, find_limits_noheap,
       or substitute_callout modifiers.

       Similarly, for testing purposes, if the null_subject or
       null_replacement modifier is set, the subject or replacement
       string pointers are passed as NULL, respectively, to the relevant


       By default, pcre2test uses the standard PCRE2 matching function,
       pcre2_match() to match each subject line. PCRE2 also supports an
       alternative matching function, pcre2_dfa_match(), which operates
       in a different way, and has some restrictions. The differences
       between the two functions are described in the pcre2matching

       If the dfa modifier is set, the alternative matching function is
       used.  This function finds all possible matches at a given point
       in the subject. If, however, the dfa_shortest modifier is set,
       processing stops after the first match is found. This is always
       the shortest possible match.

DEFAULT OUTPUT FROM pcre2test         top

       This section describes the output when the normal matching
       function, pcre2_match(), is being used.

       When a match succeeds, pcre2test outputs the list of captured
       substrings, starting with number 0 for the string that matched
       the whole pattern.  Otherwise, it outputs "No match" when the
       return is PCRE2_ERROR_NOMATCH, or "Partial match:" followed by
       the partially matching substring when the return is
       PCRE2_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, pcre2test outputs the PCRE2 negative error
       number and a short descriptive phrase. If the error is a failed
       UTF string check, the code unit offset of the start of the
       failing character is also output. Here is an example of an
       interactive pcre2test run.

         $ pcre2test
         PCRE2 version 10.22 2016-07-29

           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 shown by pcre2test unless the allcaptures modifier is
       specified. 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
       aftertext modifier is set, the output for substring 0 is followed
       by the the rest of the subject string, identified by "0+" like

           re> /cat/aftertext
         data> cataract
          0: cat
          0+ aract

       If global matching is requested, 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 the offset modifier is past the end of the subject

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

       Note that whereas patterns can be continued over several lines (a
       plain ">" prompt is used for continuations), subject lines may
       not. However newlines can be included in a subject by means of
       the \n escape (or \r, \r\n, etc., depending on the newline
       sequence setting).


       When the alternative matching function, pcre2_dfa_match(), is
       used, 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\=dfa
          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 PCRE2_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, \b, or \B was involved.
       (\K is not supported for DFA matching.)

       If global matching is requested, 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\=dfa
          0: tangerine
          1: tang
          2: tan
          0: tang
          1: tan
          0: tan

       The alternative matching function does not support substring
       capture, so the modifiers that are concerned with captured
       substrings are not relevant.


       When the alternative matching function has given the
       PCRE2_ERROR_PARTIAL return, indicating that the subject partially
       matched the pattern, you can restart the match with additional
       subject data by means of the dfa_restart modifier. For example:

         data> 23ja\=ps,dfa
         Partial match: 23ja
         data> n05\=dfa,dfa_restart
          0: n05

       For further information about partial matching, see the
       pcre2partial documentation.

CALLOUTS         top

       If the pattern contains any callout requests, pcre2test's callout
       function is called during matching unless callout_none is
       specified. This works with both matching functions, and with JIT,
       though there are some differences in behaviour. The output for
       callouts with numerical arguments and those with string arguments
       is slightly different.

   Callouts with numerical arguments

       By default, the callout function displays the callout number, the
       start and current positions in the subject 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, and when the next
       pattern item was \d. Just one circumflex is output if the start
       and current positions are the same, or if the current position
       precedes the start position, which can happen if the callout is
       in a lookbehind assertion.

       Callouts numbered 255 are assumed to be automatic callouts,
       inserted as a result of the auto_callout 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]\*/auto_callout
         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/auto_callout
         data> abc
          +0 ^       a
          +1 ^^      (*MARK:X)
         +10 ^^      b
         Latest Mark: X
         +11 ^ ^     c
         +12 ^  ^
          0: abc

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

   Callouts with string arguments

       The output for a callout with a string argument is similar,
       except that instead of outputting a callout number before the
       position indicators, the callout string and its offset in the
       pattern string are output before the reflection of the subject
       string, and the subject string is reflected for each callout. For

           re> /^ab(?C'first')cd(?C"second")ef/
         data> abcdefg
         Callout (7): 'first'
             ^ ^         c
         Callout (20): "second"
             ^   ^       e
          0: abcdef

   Callout modifiers

       The callout function in pcre2test returns zero (carry on
       matching) by default, but you can use a callout_fail modifier in
       a subject line to change this and other parameters of the callout
       (see below).

       If the callout_capture modifier is set, the current captured
       groups are output when a callout occurs. This is useful only for
       non-DFA matching, as pcre2_dfa_match() does not support
       capturing, so no captures are ever shown.

       The normal callout output, showing the callout number or pattern
       offset (as described above) is suppressed if the callout_no_where
       modifier is set.

       When using the interpretive matching function pcre2_match()
       without JIT, setting the callout_extra modifier causes additional
       output from pcre2test's callout function to be generated. For the
       first callout in a match attempt at a new starting position in
       the subject, "New match attempt" is output. If there has been a
       backtrack since the last callout (or start of matching if this is
       the first callout), "Backtrack" is output, followed by "No other
       matching paths" if the backtrack ended the previous match
       attempt. For example:

          re> /(a+)b/auto_callout,no_start_optimize,no_auto_possess
         data> aac\=callout_extra
         New match attempt
          +0 ^       (
          +1 ^       a+
          +3 ^ ^     )
          +4 ^ ^     b
          +3 ^^      )
          +4 ^^      b
         No other matching paths
         New match attempt
          +0  ^      (
          +1  ^      a+
          +3  ^^     )
          +4  ^^     b
         No other matching paths
         New match attempt
          +0   ^     (
          +1   ^     a+
         No other matching paths
         New match attempt
          +0    ^    (
          +1    ^    a+
         No match

       Notice that various optimizations must be turned off if you want
       all possible matching paths to be scanned. If no_start_optimize
       is not used, there is an immediate "no match", without any
       callouts, because the starting optimization fails to find "b" in
       the subject, which it knows must be present for any match. If
       no_auto_possess is not used, the "a+" item is turned into "a++",
       which reduces the number of backtracks.

       The callout_extra modifier has no effect if used with the DFA
       matching function, or with JIT.

   Return values from callouts

       The default return from the callout function is zero, which
       allows matching to continue. The callout_fail modifier can be
       given one or two numbers. If there is only one number, 1 is
       returned instead of 0 (causing matching to backtrack) when a
       callout of that number is reached. If two numbers (<n>:<m>) are
       given, 1 is returned when callout <n> is reached and there have
       been at least <m> callouts. The callout_error modifier is
       similar, except that PCRE2_ERROR_CALLOUT is returned, causing the
       entire matching process to be aborted. If both these modifiers
       are set for the same callout number, callout_error takes
       precedence. Note that callouts with string arguments are always
       given the number zero.

       The callout_data modifier can be given an unsigned or a negative
       number.  This is set as the "user data" that is passed to the
       matching function, and passed back when the callout function is
       invoked. Any value other than zero is used as a return from
       pcre2test's callout function.

       Inserting callouts can be helpful when using pcre2test to check
       complicated regular expressions. For further information about
       callouts, see the pcre2callout documentation.


       When pcre2test is outputting text in the compiled version of a
       pattern, bytes other than 32-126 are always treated as non-
       printing characters and are therefore shown as hex escapes.

       When pcre2test 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 locale modifier).
       In this case, the isprint() function is used to distinguish
       printing and non-printing characters.


       It is possible to save compiled patterns on disc or elsewhere,
       and reload them later, subject to a number of restrictions. JIT
       data cannot be saved. The host on which the patterns are reloaded
       must be running the same version of PCRE2, with the same code
       unit width, and must also have the same endianness, pointer width
       and PCRE2_SIZE type. Before compiled patterns can be saved they
       must be serialized, that is, converted to a stream of bytes. A
       single byte stream may contain any number of compiled patterns,
       but they must all use the same character tables. A single copy of
       the tables is included in the byte stream (its size is 1088

       The functions whose names begin with pcre2_serialize_ are used
       for serializing and de-serializing. They are described in the
       pcre2serialize documentation. In this section we describe the
       features of pcre2test that can be used to test these functions.

       Note that "serialization" in PCRE2 does not convert compiled
       patterns to an abstract format like Java or .NET. It just makes a
       reloadable byte code stream.  Hence the restrictions on reloading
       mentioned above.

       In pcre2test, when a pattern with push modifier is successfully
       compiled, it is pushed onto a stack of compiled patterns, and
       pcre2test expects the next line to contain a new pattern (or
       command) instead of a subject line. By contrast, the pushcopy
       modifier causes a copy of the compiled pattern to be stacked,
       leaving the original available for immediate matching. By using
       push and/or pushcopy, a number of patterns can be compiled and
       retained. These modifiers are incompatible with posix, and
       control modifiers that act at match time are ignored (with a
       message) for the stacked patterns. The jitverify modifier applies
       only at compile time.

       The command

         #save <filename>

       causes all the stacked patterns to be serialized and the result
       written to the named file. Afterwards, all the stacked patterns
       are freed. The command

         #load <filename>

       reads the data in the file, and then arranges for it to be de-
       serialized, with the resulting compiled patterns added to the
       pattern stack. The pattern on the top of the stack can be
       retrieved by the #pop command, which must be followed by lines of
       subjects that are to be matched with the pattern, terminated as
       usual by an empty line or end of file. This command may be
       followed by a modifier list containing only control modifiers
       that act after a pattern has been compiled. In particular, hex,
       posix, posix_nosub, push, and pushcopy are not allowed, nor are
       any option-setting modifiers.  The JIT modifiers are, however
       permitted. Here is an example that saves and reloads two

         #save tempfile
         #load tempfile
         #pop info

         #pop jit,bincode

       If jitverify is used with #pop, it does not automatically imply
       jit, which is different behaviour from when it is used on a

       The #popcopy command is analogous to the pushcopy modifier in
       that it makes current a copy of the topmost stack pattern,
       leaving the original still on the stack.

SEE ALSO         top

       pcre2(3), pcre2api(3), pcre2callout(3), pcre2jit,
       pcre2matching(3), pcre2partial(d), pcre2pattern(3),

AUTHOR         top

       Philip Hazel
       Retired from University Computing Service
       Cambridge, England.

REVISION         top

       Last updated: 11 August 2023
       Copyright (c) 1997-2023 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 fetched from
       ⟨https://github.com/PhilipHazel/pcre2.git⟩ on 2023-12-22.  If you
       discover any rendering problems in this HTML version 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
       manual page), send a mail to man-pages@man7.org

PCRE 10.43                      11 August                   PCRE2TEST(1)