pcre2test man page

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• SYNOPSIS
• PCRE2's 8-BIT, 16-BIT AND 32-BIT LIBRARIES
• INPUT ENCODING
• COMMAND LINE OPTIONS
• DESCRIPTION
• COMMAND LINES
• MODIFIER SYNTAX
• PATTERN SYNTAX
• SUBJECT LINE SYNTAX
• PATTERN MODIFIERS
• SUBJECT MODIFIERS
• THE ALTERNATIVE MATCHING FUNCTION
• DEFAULT OUTPUT FROM pcre2test
• OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION
• RESTARTING AFTER A PARTIAL MATCH
• CALLOUTS
• NON-PRINTING CHARACTERS
• SAVING AND RESTORING COMPILED PATTERNS
• SEE ALSO
• AUTHOR
• REVISION

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.

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 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 action.

The input is processed 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 zeros.

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 and some patterns, 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. 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 environment:
               either 0x15 or 0x25
               0 if used in an ASCII/Unicode environment
               exit code is always 0
  linksize   the configured internal link size (2, 3, or 4)
               exit code is set to the link size
  newline    the default newline setting:
               CR, LF, CRLF, ANYCRLF, ANY, or NUL
               exit code is always 0
  bsr        the default setting for what \R matches:
               ANYCRLF or ANY
               exit code is always 0

  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

  0  JIT is available and usable
  1  JIT is available but cannot allocate executable memory
  2  JIT is not available
  3  Unexpected return from test call to pcre2_jit_compile()

-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 compilation.

-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.

-jitfast 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 path".

-jitverify 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 recognized.

-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 recognized.

-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 modifiers.

-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 modifiers.

-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.

-version Output the PCRE2 version number and then exit.

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 explicitly.

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.

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 recognized:

  #forbid_utf

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 output.

  #load <filename>

  #loadtables <filename>

  #newline_default [<newline-list>]

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 example:

  #newline_default LF Any anyCRLF

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>

  #perltest

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>]

  #save <filename>

  #subject <modifier-list>

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:

  /abc/ig,newline=cr,jit=3

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

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

  /abc\/def/

  /abc/\

  /abc\/

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)
  \N{U+hh...} unicode character (any number of hex digits)
  \r          carriage return (\x0d)
  \t          tab (\x09)
  \v          vertical tab (\x0b)
  \ddd        octal number (up to 3 octal digits); represent a single
                code point unless larger than 255 with the 8-bit library
  \o{dd...}   octal number (any number of octal digits} representing a
                character in UTF mode or a code point
  \xhh        hexadecimal byte (up to 2 hex digits)
  \x{hh...}   hexadecimal number (up to 8 hex digits) representing a
                character in UTF mode or a code point

Note that even in UTF-8 mode, \xhh (and depending of how large, \ddd) describe one byte rather than one character; 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, only generating more than one byte if the value is greater than 127. To avoid the ambiguity it is preferred to use \N{U+hh...} when describing characters. When testing the 8-bit library not in UTF-8 mode, \x{hh} generates one byte for values that could fit on it, and causes an error for greater values.

When testing the 16-bit library, not 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.

When testing the 32-bit library, not 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:

  \[<characters>]{<count>}

  \[abc]{4}

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

  abc\=notbol,notempty

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

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 command.

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 PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK
      allow_surrogate_escapes   set PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES
      alt_bsux                  set PCRE2_ALT_BSUX
      alt_circumflex            set PCRE2_ALT_CIRCUMFLEX
      alt_extended_class        set PCRE2_ALT_EXTENDED_CLASS
      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 PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL
  /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_callout             set PCRE2_EXTRA_NEVER_CALLOUT
      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_bs0                    set PCRE2_EXTRA_NO_BS0
      no_dotstar_anchor         set PCRE2_NO_DOTSTAR_ANCHOR
      no_start_optimize         set PCRE2_NO_START_OPTIMIZE
      no_utf_check              set PCRE2_NO_UTF_CHECK
      python_octal              set PCRE2_EXTRA_PYTHON_OCTAL
      turkish_casing            set PCRE2_EXTRA_TURKISH_CASING
      ucp                       set PCRE2_UCP
      ungreedy                  set PCRE2_UNGREEDY
      use_offset_limit          set PCRE2_USE_OFFSET_LIMIT
      utf                       set PCRE2_UTF

      optimization_full      enable all optional optimizations
      optimization_none      disable all optional optimizations
      auto_possess           auto-possessify variable quantifiers
      auto_possess_off       don't auto-possessify variable quantifiers
      dotstar_anchor         anchor patterns starting with .*
      dotstar_anchor_off     don't anchor patterns starting with .*
      start_optimize         enable pre-scan of subject string
      start_optimize_off     disable pre-scan of subject string

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.

  /B  bincode                   show binary code without lengths
      bsr=[anycrlf|unicode]     specify \R handling
      callout_info              show callout information
      convert=<options>         request foreign pattern conversion
      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
      expand                    expand repetition syntax in pattern
      framesize                 show matching frame size
      fullbincode               show binary code with lengths
  /I  info                      show info about compiled pattern
      hex                       unquoted characters are hexadecimal
      jit[=<number>]            use JIT
      jitfast                   use JIT fast path
      jitverify                 verify JIT use
      locale=<name>             use this locale
      max_pattern_compiled      ) set maximum compiled pattern
                 _length=<n>    )   length (bytes)
      max_pattern_length=<n>    set maximum pattern length (code units)
      max_varlookbehind=<n>     set maximum variable lookbehind length
      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 stack
      pushcopy                  push a copy onto the stack
      pushtablescopy            push a copy with tables onto the stack
      stackguard=<number>       test the stackguard feature
      subject_literal           treat all subject lines as literal
      tables=[0|1|2|3]          select internal tables
      use_length                do not zero-terminate the pattern
      utf8_input                treat input as UTF-8

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).

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

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.

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).

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.

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 characters:

  /ab 32 59/hex

  /ab "literal" 32/hex

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.

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.

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.

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

  \[<characters>]{<count>}

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.

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

  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 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 match.

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

  /pattern/locale=fr_FR

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 example:

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

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.

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).

The max_pattern_compiled_length modifier sets a limit, in bytes, to the amount of memory used by a compiled pattern. Breaching the limit causes a compilation error. The default is the largest number a PCRE2_SIZE variable can hold (essentially unlimited).

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 of
  ucp                REG_UCP        )   the POSIX standard
  utf                REG_UTF8       )

  /abc/posix,regerror_buffsize=20

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.

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.

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
        pcre2_chartables.c.dist
  2   a set of tables defining ISO 8859 characters
  3   a set of tables loaded by the #loadtables command

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 relevant
      substitute_callout          use substitution callouts
      substitute_case_callout=<string> use substitution case callouts
      substitute_extended         use PCRE2_SUBSTITUTE_EXTENDED
      substitute_literal          use PCRE2_SUBSTITUTE_LITERAL
      substitute_matched          use PCRE2_SUBSTITUTE_MATCHED
      substitute_overflow_length  use PCRE2_SUBSTITUTE_OVERFLOW_LENGTH
      substitute_replacement_only use PCRE2_SUBSTITUTE_REPLACEMENT_ONLY
      substitute_skip=<n>         skip substitution <n>
      substitute_stop=<n>         skip substitution <n> and following
      substitute_unknown_unset    use PCRE2_SUBSTITUTE_UNKNOWN_UNSET
      substitute_unset_empty      use PCRE2_SUBSTITUTE_UNSET_EMPTY

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.

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.

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

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 check.

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 dependent.

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

The following modifiers set options for pcre2_match() or pcre2_dfa_match(). See pcre2api for a description of their effects.

      anchored                   set PCRE2_ANCHORED
      copy_matched_subject       set PCRE2_COPY_MATCHED_SUBJECT
      endanchored                set PCRE2_ENDANCHORED
      dfa_restart                set PCRE2_DFA_RESTART
      dfa_shortest               set PCRE2_DFA_SHORTEST
      disable_recurseloop_check  set PCRE2_DISABLE_RECURSELOOP_CHECK
      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

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 matching.

      posix_startend=<n>[:<m>]

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
      allusedtext                show all consulted text (non-JIT only)
      allvector                  show the entire ovector
      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
      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 limits
      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 (Kbytes)
      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_case_callout=<string> use substitution case callouts
      substitute_extedded        use PCRE2_SUBSTITUTE_EXTENDED
      substitute_literal         use PCRE2_SUBSTITUTE_LITERAL
      substitute_matched         use PCRE2_SUBSTITUTE_MATCHED
      substitute_overflow_length use PCRE2_SUBSTITUTE_OVERFLOW_LENGTH
      substitute_replacement_only use PCRE2_SUBSTITUTE_REPLACEMENT_ONLY
      substitute_skip=<n>        skip substitution number n
      substitute_stop=<n>        skip substitution number n and greater
      substitute_unknown_unset   use PCRE2_SUBSTITUTE_UNKNOWN_UNSET
      substitute_unset_empty     use PCRE2_SUBSTITUTE_UNSET_EMPTY
      zero_terminate             pass the subject as zero-terminated

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 number.

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 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
      ^^^

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 present.

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.

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.

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.

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:

   abcd\=copy=1,copy=3,get=G1

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.

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

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:

  /abc/replace=xxx
      =abc=abc=
   1: =xxx=abc=
      =abc=abc=\=global
   2: =xxx=xxx=

  /abc/
      123abc123\=replace=[10]XYZ
   1: 123XYZ123
      123abc123\=replace=[9]XYZ
  Failed: error -47: no more memory

  /abc/substitute_overflow_length
      123abc123\=replace=[9]XYZ
  Failed: error -47: no more memory: 10 code units are needed

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 input and output strings are output. For example:

  /abc/g,replace=<$0>,substitute_callout
      abcdefabcpqr
   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

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 example:

  /abc/g,replace=<$0>,substitute_skip=1
      abcdefabcpqr
   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
      abcdefabcpqr\=substitute_stop=1
   1(1) Old 0 3 "abc" New 0 5 "<abc> STOPPED"
   1: abcdefabcpqr

If the substitute_case_callout=<string> modifier is set, a substitution case callout function is set up. The callout function is called for each substituted character which is to be case-transformed, and the mapping used is specified by the modifier's string argument.

The string argument is parsed as four-character blocks, with each block interpreted as "<input><lower><upper><title>". The input character is used to find a matching block, and the corresponding character is then returned. For example, to specify a custom uppercasing of the letter "a" to "Z":

  /a/g,replace=\U$0,substitute_extended,substitute_case_callout=a.Z.
      a
   1: Z

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.

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.

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 omitted.

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 used.

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.

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.

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.

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.

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

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.

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.

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.

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 functions.

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 documentation.

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.

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

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

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

    re> /\Bi(\w\w)/g
  data> Mississippi
   0: iss
   1: ss
   0: iss
   1: ss
   0: ipp
   1: pp

    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

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

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:

    re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/
  data> 23ja\=ps,dfa
  Partial match: 23ja
  data> n05\=dfa,dfa_restart
   0: n05

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.

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:

  --->pqrabcdef
    0    ^  ^     \d

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

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

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 example:

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

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
  --->aac
   +0 ^       (
   +1 ^       a+
   +3 ^ ^     )
   +4 ^ ^     b
  Backtrack
  --->aac
   +3 ^^      )
   +4 ^^      b
  Backtrack
  No other matching paths
  New match attempt
  --->aac
   +0  ^      (
   +1  ^      a+
   +3  ^^     )
   +4  ^^     b
  Backtrack
  No other matching paths
  New match attempt
  --->aac
   +0   ^     (
   +1   ^     a+
  Backtrack
  No other matching paths
  New match attempt
  --->aac
   +0    ^    (
   +1    ^    a+
  No match

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

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 bytes).

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>

  #load <filename>

  /abc/push
  /xyz/push
  #save tempfile
  #load tempfile
  #pop info
  xyz

  #pop jit,bincode
  abc

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.

pcre2(3), pcre2api(3), pcre2callout(3), pcre2jit, pcre2matching(3), pcre2partial(d), pcre2pattern(3), pcre2serialize(3).

Philip Hazel
Retired from University Computing Service
Cambridge, England.

Last updated: 04 December 2024
Copyright © 1997-2024 University of Cambridge.

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