pcre2/doc/pcre2test.txt

PCRE2TEST(1)                General Commands Manual               PCRE2TEST(1)



NAME
       pcre2test - a program for testing Perl-compatible regular expressions.

SYNOPSIS

       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  documenta-
       tion.  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  func-
       tion  options, control how the subject is processed, and what output is
       produced.

       As the original fairly simple PCRE library evolved,  it  acquired  many
       different  features,  and  as  a  result, the original pcretest program
       ended up with a lot of options in a messy, arcane syntax,  for  testing
       all the features. The move to the new PCRE2 API provided an opportunity
       to re-implement the test program as pcre2test, with a cleaner  modifier
       syntax.  Nevertheless,  there are still 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

       Different versions of the PCRE2 library can be built to support charac-
       ter  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- 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 struc-
       tures  are  given  in  generic  form,  for example, pcre_compile(). The
       actual names used in the libraries have a suffix _8, _16,  or  _32,  as
       appropriate.


INPUT ENCODING

       Input  to  pcre2test is processed line by line, either by calling the C
       library's fgets() function, or via the libreadline library (see below).
       The  input  is  processed using using C's string functions, so must not
       contain binary zeroes, even though in Unix-like  environments,  fgets()
       treats any bytes other than newline as data characters. In some Windows
       environments character 26 (hex 1A) causes an immediate end of file, and
       no further data is read.

       For  maximum portability, therefore, it is safest to avoid non-printing
       characters in pcre2test input files. There is a facility for specifying
       a pattern's characters as hexadecimal pairs, thus making it possible to
       include binary zeroes in a pattern for testing purposes. Subject  lines
       are processed for backslash escapes, which makes it possible to include
       any data value.


COMMAND LINE OPTIONS

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

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

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

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

       -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.

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

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

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

                   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  inter-
                 nal 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().

       -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.

       -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 megabytes.

       -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 out-
                 put 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 out-
                 put.

       -version  Output the PCRE2 version number and then exit.


DESCRIPTION

       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 pat-
       tern. 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.

       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.


COMMAND LINES

       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

       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  informa-
       tion, to avoid cluttering up test output.

         #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.

         #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  con-
       tain  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 com-
       piled 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, ANY-
       CRLF, or ANY (in upper or lower case), for example:

         #newline_default LF Any anyCRLF

       If the default newline is in the list, this command has no effect. Oth-
       erwise,  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
       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 subse-
       quent patterns. Modifiers on a pattern can change these settings.

         #perltest

       The appearance of this line causes all subsequent modifier settings  to
       be checked for compatibility with the perltest.sh script, which is used
       to confirm that Perl gives the same results as PCRE2. Also, apart  from
       comment  lines,  none of the other command lines are permitted, because
       they and many of the modifiers are specific to  pcre2test,  and  should
       not  be  used in test files that are also processed by perltest.sh. The
       #perltest command helps detect tests that are accidentally put  in  the
       wrong file.

         #pop [<modifiers>]

       This  command  is used to manipulate the stack of compiled patterns, as
       described in the section entitled "Saving and restoring  compiled  pat-
       terns" 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  pat-
       terns" below.

         #subject <modifier-list>

       This  command  sets  a default modifier list that applies to all subse-
       quent subject lines. Modifiers on a subject line can change these  set-
       tings.


MODIFIER SYNTAX

       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 charac-
       ters, 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 let-
       ters, 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

       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

       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 delim-
       iter within the pattern by escaping it with a backslash, for example

         /abc\/def/

       If  you do this, the escape and the delimiter form part of the pattern,
       but since the delimiters are all non-alphanumeric, this does not affect
       its  interpretation.  If  the terminating delimiter is immediately fol-
       lowed by a backslash, for example,

         /abc/\

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

         /abc\/

       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 regu-
       lar expression.

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


SUBJECT LINE SYNTAX

       Before   each   subject   line   is   passed   to   pcre2_match()    or
       pcre2_dfa_match(), leading and trailing white space is removed, and the
       line is scanned for backslash escapes. 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 mode
         \o{dd...}  octal character (any number of octal digits}
         \xhh       hexadecimal byte (up to 2 hex digits)
         \x{hh...}  hexadecimal character (any number of hex digits)

       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  hexa-
       decimal  digits  inside  the  braces; invalid values provoke error mes-
       sages.

       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:

         \[<characters>]{<count>}

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

         \[abc]{4}

       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:

         abc\=notbol,notempty

       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.


PATTERN MODIFIERS

       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.

   Setting compilation options

       The  following modifiers set options for pcre2_compile(). The most com-
       mon ones have single-letter abbreviations. See pcre2api for a  descrip-
       tion of their effects.

             allow_empty_class         set PCRE2_ALLOW_EMPTY_CLASS
             alt_bsux                  set PCRE2_ALT_BSUX
             alt_circumflex            set PCRE2_ALT_CIRCUMFLEX
             alt_verbnames             set PCRE2_ALT_VERBNAMES
             anchored                  set PCRE2_ANCHORED
             auto_callout              set PCRE2_AUTO_CALLOUT
         /i  caseless                  set PCRE2_CASELESS
             dollar_endonly            set PCRE2_DOLLAR_ENDONLY
         /s  dotall                    set PCRE2_DOTALL
             dupnames                  set PCRE2_DUPNAMES
         /x  extended                  set PCRE2_EXTENDED
             firstline                 set PCRE2_FIRSTLINE
             match_unset_backref       set PCRE2_MATCH_UNSET_BACKREF
         /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
             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 compilation controls

       The following modifiers  affect  the  compilation  process  or  request
       information about the pattern:

             bsr=[anycrlf|unicode]     specify \R handling
         /B  bincode                   show binary code without lengths
             callout_info              show callout information
             debug                     same as info,fullbincode
             fullbincode               show binary code with lengths
         /I  info                      show info about compiled pattern
             hex                       pattern is coded in hexadecimal
             jit[=<number>]            use JIT
             jitfast                   use JIT fast path
             jitverify                 verify JIT use
             locale=<name>             use this locale
             max_pattern_length=<n>    set the maximum pattern length
             memory                    show memory used
             newline=<type>            set newline type
             null_context              compile with a NULL context
             parens_nest_limit=<n>     set maximum parentheses depth
             posix                     use the POSIX API
             push                      push compiled pattern onto the stack
             stackguard=<number>       test the stackguard feature
             tables=[0|1|2]            select internal tables

       The effects of these modifiers are described in the following sections.

   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 is
       specified when PCRE2 is built, with the default default being 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, or ANY (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 dif-
       ferent internal link sizes and different code  unit  widths.  By  using
       bincode,  the  same  regression tests can be used in different environ-
       ments.

       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
         Capturing subpattern 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
         Capturing subpattern 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  callout_info  modifier requests information about all the callouts
       in the pattern. A list of them is output at the end of any other infor-
       mation 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).

   Specifying a pattern in hex

       The hex modifier specifies that the characters of the pattern are to be
       interpreted as pairs of hexadecimal digits. White  space  is  permitted
       between pairs. For example:

         /ab 32 59/hex

       This  feature  is  provided  as a way of creating patterns that contain
       binary zero and other non-printing characters.  By  default,  pcre2test
       passes  patterns  as zero-terminated strings to pcre2_compile(), giving
       the length as PCRE2_ZERO_TERMINATED. However, for patterns specified in
       hexadecimal, the actual length of the pattern is passed.

   Generating long repetitive patterns

       Some  tests use long patterns that are very repetitive. Instead of cre-
       ating 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>}

       are expanded before the pattern is passed to pcre2_compile(). For exam-
       ple, \[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.

       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 rec-
       ognized 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  com-
       plete 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 automati-
       cally 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  san-
       ity  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 compila-
       tion 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.

   Setting a locale

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

         /pattern/locale=fr_FR

       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_com-
       pile() 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 charac-
       ter 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 example:

           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 modifier causes pcre2test to call PCRE2 via the POSIX wrap-
       per API rather than its  native  API.  This  supports  only  the  8-bit
       library.   Note  that  it  does not imply POSIX matching semantics; for
       more detail see the pcre2posix documentation. When  the  POSIX  API  is
       being  used,  the  following pattern modifiers set options for the reg-
       comp() function:

         caseless           REG_ICASE
         multiline          REG_NEWLINE
         no_auto_capture    REG_NOSUB
         dotall             REG_DOTALL     )
         ungreedy           REG_UNGREEDY   ) These options are not part of
         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:

         /abc/posix,regerror_buffsize=20

       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 cause an error.

   Testing the stack guard feature

       The  /stackguard  modifier  is  used  to test the use of pcre2_set_com-
       pile_recursion_guard(), a function that is  provided  to  enable  stack
       availability  to  be checked during compilation (see the pcre2api docu-
       mentation 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, or 2. 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 be-
       haviour 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

       In  table 2, some characters whose codes are greater than 128 are iden-
       tified as letters, digits, spaces,  etc.  Setting  alternate  character
       tables and a locale are mutually exclusive.

   Setting certain match controls

       The following modifiers are really subject modifiers, and are described
       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. They may not appear in #pattern commands. These mod-
       ifiers do not affect the compilation process.

             aftertext                  show text after match
             allaftertext               show text after captures
             allcaptures                show all captures
             allusedtext                show all consulted text
         /g  global                     global matching
             mark                       show mark values
             replace=<string>           specify a replacement string
             startchar                  show starting character when relevant
             substitute_extended        use PCRE2_SUBSTITUTE_EXTENDED
             substitute_overflow_length use PCRE2_SUBSTITUTE_OVERFLOW_LENGTH
             substitute_unknown_unset   use PCRE2_SUBSTITUTE_UNKNOWN_UNSET
             substitute_unset_empty     use PCRE2_SUBSTITUTE_UNSET_EMPTY

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

   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  pat-
       terns" below.  The push modifier is incompatible with compilation modi-
       fiers such as global that act at match time. Any that are specified are
       ignored,  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 this pattern.


SUBJECT MODIFIERS

       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 effects.

             anchored                  set PCRE2_ANCHORED
             dfa_restart               set PCRE2_DFA_RESTART
             dfa_shortest              set PCRE2_DFA_SHORTEST
             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 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().
       Any other modifiers cause an error.

   Setting match controls

       The following modifiers affect the matching process  or  request  addi-
       tional  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.

             aftertext                  show text after match
             allaftertext               show text after captures
             allcaptures                show all captures
             allusedtext                show all consulted text (non-JIT only)
             altglobal                  alternative global matching
             callout_capture            show captures at callout time
             callout_data=<n>           set a value to pass via callouts
             callout_fail=<n>[:<m>]     control callout failure
             callout_none               do not supply a callout function
             copy=<number or name>      copy captured substring
             dfa                        use pcre2_dfa_match()
             find_limits                find match and recursion limits
             get=<number or name>       extract captured substring
             getall                     extract all captured substrings
         /g  global                     global matching
             jitstack=<n>               set size of JIT stack
             mark                       show mark values
             match_limit=<n>            set a match limit
             memory                     show memory usage
             null_context               match with a NULL context
             offset=<n>                 set starting offset
             offset_limit=<n>           set offset limit
             ovector=<n>                set size of output vector
             recursion_limit=<n>        set a recursion limit
             replace=<string>           specify a replacement string
             startchar                  show startchar when relevant
             startoffset=<n>            same as offset=<n>
             substitute_extedded        use PCRE2_SUBSTITUTE_EXTENDED
             substitute_overflow_length use PCRE2_SUBSTITUTE_OVERFLOW_LENGTH
             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 effects of these modifiers are described in the following sections.

   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 sub-
       strings as well as the main matched substring. In each case the remain-
       der 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.
       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
       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  indi-
       cated  in  the output by '<' or '>' characters underneath them. Here is
       an example:

           re> /(?<=pqr)abc(?=xyz)/
         data> 123pqrabcxyz456\=allusedtext
          0: pqrabcxyz
             <<<   >>>

       This 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 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.   How-
       ever, these two modifiers are mutually exclusive.

   Showing the value of all capture groups

       The allcaptures modifier requests that the values of all potential cap-
       tured 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>".

   Testing callouts

       A  callout function is supplied when pcre2test calls the library match-
       ing functions, unless callout_none is specified. If callout_capture  is
       set, the current captured groups are output when a callout occurs.

       The  callout_fail modifier can be given one or two numbers. If there is
       only one number, 1 is returned instead of 0 when a callout of that num-
       ber  is  reached.  If two numbers are given, 1 is returned when callout
       <n> is reached for the <m>th time. Note that callouts with string argu-
       ments  are  always  given  the  number zero. See "Callouts" below for a
       description of the output when a callout it taken.

       The callout_data modifier can be given an unsigned or a  negative  num-
       ber.   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.

   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 lookbe-
       hind 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_sub-
       string_copy_xxx() and pcre2_substring_get_xxx() functions.  They can be
       given more than once, and each can specify a group name or number,  for
       example:

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

       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  num-
       bered groups and an empty name to cancel all named groups.

       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. 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.

       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  pro-
       vides 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_overflow_length  PCRE2_SUBSTITUTE_OVERFLOW_LENGTH
         substitute_unknown_unset    PCRE2_SUBSTITUTE_UNKNOWN_UNSET
         substitute_unset_empty      PCRE2_SUBSTITUTE_UNSET_EMPTY


       After a successful substitution, the modified string  is  output,  pre-
       ceded  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=

       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:

         /abc/
             123abc123\=replace=[10]XYZ
          1: 123XYZ123
             123abc123\=replace=[9]XYZ
         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  sub-
       stitute_overflow_length  modifier),  pcre2_substitute() continues to go
       through the motions of matching and substituting, 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:

         /abc/substitute_overflow_length
             123abc123\=replace=[9]XYZ
         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().

   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 kilobytes.
       Providing a stack that is larger than the default 32K is necessary only
       for very complicated patterns.

   Setting match and recursion limits

       The  match_limit and recursion_limit modifiers set the appropriate lim-
       its in the match context. These values are ignored when the find_limits
       modifier is specified.

   Finding minimum limits

       If  the  find_limits modifier is present, pcre2test calls pcre2_match()
       several times, setting  different  values  in  the  match  context  via
       pcre2_set_match_limit()  and pcre2_set_recursion_limit() until it finds
       the minimum values for each parameter that allow pcre2_match() to  com-
       plete without error.

       If JIT is being used, only the match limit is relevant. If DFA matching
       is being used, neither limit is relevant, and this modifier is  ignored
       (with a warning message).

       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.   The
       match_limit_recursion number is a measure of how  much  stack  (or,  if
       PCRE2  is  compiled with NO_RECURSE, how much heap) memory is needed to
       complete the match attempt.

   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 all memory  allocation  and
       freeing calls that occur during a match operation.

   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 characters.

   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 modi-
       fier 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_cre-
       ate_from_pattern() to be called, in order to create a  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.)

   Passing the subject as zero-terminated

       By default, the subject string is passed to a native API matching func-
       tion 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 has no effect, as there is no
       facility for passing a length.)

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

   Passing a NULL context

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


THE ALTERNATIVE MATCHING FUNCTION

       By default,  pcre2test  uses  the  standard  PCRE2  matching  function,
       pcre2_match() to match each subject line. PCRE2 also supports an alter-
       native matching function, pcre2_dfa_match(), which operates in  a  dif-
       ferent  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 sub-
       ject. 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

       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 sub-
       strings, 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 9.00 2014-05-10

           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 defi-
       nition  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 this:

           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 string):

           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).


OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION

       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 asser-
       tion, \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.


RESTARTING AFTER A PARTIAL MATCH

       When the alternative matching function has given  the  PCRE2_ERROR_PAR-
       TIAL 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\=P,dfa
         Partial match: 23ja
         data> n05\=dfa,dfa_restart
          0: n05

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


CALLOUTS

       If the pattern contains any callout requests, pcre2test's callout func-
       tion  is called during matching unless callout_none is specified.  This
       works with both matching functions.

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

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

       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:

         --->pqrabcdef
           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.

       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*

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

           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 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 example:

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


NON-PRINTING CHARACTERS

       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.


SAVING AND RESTORING COMPILED PATTERNS

       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,  con-
       verted  to a stream of bytes. A single byte stream may contain any num-
       ber 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 pcre2serial-
       ize  documentation.  In  this  section  we  describe  the  features  of
       pcre2test that can be used to test these functions.

       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 this means, a number of patterns can be compiled and retained.
       The  push  modifier  is  incompatible with posix, and control modifiers
       that act at match time are ignored (with a message). The jitverify mod-
       ifier 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-serial-
       ized, with the resulting compiled patterns added to the pattern  stack.
       The  pattern  on the top of the stack can be retrieved by the #pop com-
       mand, 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, and push are not allowed, nor are  any  option-
       setting  modifiers.   The JIT modifiers are, however permitted. Here is
       an example that saves and reloads two patterns.

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

         #pop jit,bincode
         abc

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


SEE ALSO

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


AUTHOR

       Philip Hazel
       University Computing Service
       Cambridge, England.


REVISION

       Last updated: 12 December 2015
       Copyright (c) 1997-2015 University of Cambridge.