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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 op-
       tions, 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 li-
       braries.

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  in-
       stalled.	 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 li-
       brary  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 ac-
       tual names used in the libraries	have a suffix _8, _16, or _32, as  ap-
       propriate.

INPUT ENCODING

       Input  to  pcre2test is processed line by line, either by calling the C
       library's fgets() function, or via the  libreadline  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 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  in-
       clude binary zeros.

   Input for the 16-bit	and 32-bit libraries

       When testing the	16-bit or 32-bit libraries, there is a need to be able
       to generate character code points greater than 255 in the strings  that
       are  passed to the library. For subject lines, backslash	escapes	can be
       used. In	addition, when the utf modifier	(see "Setting compilation  op-
       tions"  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  ap-
       propriate.

       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 charac-
       ter is placed in	one 16-bit or 32-bit code unit (in  the	 16-bit	 case,
       values greater than 0xffff cause	an error to occur).

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

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.

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

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

       -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 op-
		 tions 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:
				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, ANY, or NUL
				exit code is always 0
		   bsr	      the default setting for what \R matches:
				ANYCRLF	or ANY
				exit code is always 0

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

		   backslash-C	\C is supported	(not locked out)
		   ebcdic	compiled for an	EBCDIC environment
		   jit		just-in-time support is	available
		   pcre2-16	the 16-bit library was built
		   pcre2-32	the 32-bit library was built
		   pcre2-8	the 8-bit library was built
		   unicode	Unicode	support	is available

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

       -d	 Behave	as if each pattern has the debug modifier; the	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().

       -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; af-
		 ter 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 -LM 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  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. For a	speci-
       fication	of perltest.sh,	see the	comments near its beginning.

       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 ex-
       pected 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.

	 #loadtables <filename>

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

	 #newline_default [<newline-list>]

       When  PCRE2  is	built,	a default newline convention can be specified.
       This determines which characters	and/or character pairs are  recognized
       as indicating a newline in a pattern or subject string. The default can
       be overridden when a pattern is compiled. The standard test files  con-
       tain  tests  of	various	 newline  conventions, but the majority	of the
       tests expect a single linefeed to be recognized as  a  newline  by  de-
       fault.  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, ANY, or NUL (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 ex-
       ample)  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 de-
       fault newline convention, though	it is possible to set the newline con-
       vention	from  within  the  pattern. A warning is given if the posix or
       posix_nosub modifier is used when #newline_default would	set a  default
       for the non-POSIX API.

	 #pattern <modifier-list>

       This  command  sets  a default modifier list that applies to all	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, #pattern commands, and #subject commands that set	or un-
       set "mark", no 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>]
	 #popcopy [<modifiers>]

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

	 #save <filename>

       This  command  is used to save a	set of compiled	patterns to a file, as
       described in the	section	entitled "Saving and restoring	compiled  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 "an-
       chored",	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, unless the subject_literal modi-
       fier was	set for	the pattern. The following provide a means of encoding
       non-printing characters in a visible way:

	 \a	    alarm (BEL,	\x07)
	 \b	    backspace (\x08)
	 \e	    escape (\x27)
	 \f	    form feed (\x0c)
	 \n	    newline (\x0a)
	 \r	    carriage return (\x0d)
	 \t	    tab	(\x09)
	 \v	    vertical tab (\x0b)
	 \nnn	    octal character (up	to 3 octal digits); always
		      a	byte unless > 255 in UTF-8 or 16-bit or	32-bit 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  es-
       capes  that  character. A backslash followed by anything	else causes an
       error. However, if the very last	character in the line is  a  backslash
       (and  there  is	no  modifier list), it is ignored. This	gives a	way of
       passing an empty	line as	data, since a real empty line  terminates  the
       data input.

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

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(). 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.	For the	main options, there are	some single-letter ab-
       breviations  that  are  the same	as Perl	options. There is special han-
       dling for /x: if	a second x is  present,	 PCRE2_EXTENDED	 is  converted
       into  PCRE2_EXTENDED_MORE as in Perl. A third appearance	adds PCRE2_EX-
       TENDED as well, though this makes no difference to the  way  pcre2_com-
       pile()  behaves.	See pcre2api for a description of the effects of these
       options.

	     allow_empty_class	       set PCRE2_ALLOW_EMPTY_CLASS
	     allow_surrogate_escapes   set PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES
	     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
	     bad_escape_is_literal     set PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL
	 /i  caseless		       set PCRE2_CASELESS
	     dollar_endonly	       set PCRE2_DOLLAR_ENDONLY
	 /s  dotall		       set PCRE2_DOTALL
	     dupnames		       set PCRE2_DUPNAMES
	     endanchored	       set PCRE2_ENDANCHORED
	     escaped_cr_is_lf	       set PCRE2_EXTRA_ESCAPED_CR_IS_LF
	 /x  extended		       set PCRE2_EXTENDED
	 /xx extended_more	       set PCRE2_EXTENDED_MORE
	     extra_alt_bsux	       set PCRE2_EXTRA_ALT_BSUX
	     firstline		       set PCRE2_FIRSTLINE
	     literal		       set PCRE2_LITERAL
	     match_line		       set PCRE2_EXTRA_MATCH_LINE
	     match_invalid_utf	       set PCRE2_MATCH_INVALID_UTF
	     match_unset_backref       set PCRE2_MATCH_UNSET_BACKREF
	     match_word		       set PCRE2_EXTRA_MATCH_WORD
	 /m  multiline		       set PCRE2_MULTILINE
	     never_backslash_c	       set PCRE2_NEVER_BACKSLASH_C
	     never_ucp		       set PCRE2_NEVER_UCP
	     never_utf		       set PCRE2_NEVER_UTF
	 /n  no_auto_capture	       set PCRE2_NO_AUTO_CAPTURE
	     no_auto_possess	       set PCRE2_NO_AUTO_POSSESS
	     no_dotstar_anchor	       set PCRE2_NO_DOTSTAR_ANCHOR
	     no_start_optimize	       set PCRE2_NO_START_OPTIMIZE
	     no_utf_check	       set PCRE2_NO_UTF_CHECK
	     ucp		       set PCRE2_UCP
	     ungreedy		       set PCRE2_UNGREEDY
	     use_offset_limit	       set PCRE2_USE_OFFSET_LIMIT
	     utf		       set PCRE2_UTF

       As well as turning on the PCRE2_UTF option, the utf modifier causes all
       non-printing  characters	 in  output  strings  to  be printed using the
       \x{hh...} notation. Otherwise, those less than 0x100 are	output in  hex
       without	the  curly brackets. Setting utf in 16-bit or 32-bit mode also
       causes pattern and subject  strings  to	be  translated	to  UTF-16  or
       UTF-32, respectively, before being passed to library functions.

   Setting compilation controls

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

	     bsr=[anycrlf|unicode]     specify \R handling
	 /B  bincode		       show binary code	without	lengths
	     callout_info	       show callout information
	     convert=<options>	       request foreign pattern 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
	     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_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
	     posix_nosub	       use the POSIX API with REG_NOSUB
	     push		       push compiled pattern onto the stack
	     pushcopy		       push a copy 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 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	can be
       specified when PCRE2 is built; if it is not, the	default	is set to Uni-
       code.

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

   Information about a pattern

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

       The bincode modifier causes a representation of the compiled code to be
       output  after compilation. This information does	not contain length and
       offset values, which ensures that the same output is generated for 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
	 Capture group count = 1
	 Compile options: multiline
	 Overall options: caseless multiline
	 First code unit at start or follows newline
	 Subject length	lower bound = 1

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

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

       The framesize modifier shows the	size, in bytes,	of the storage	frames
       used  by	 pcre2_match()	for handling backtracking. The size depends on
       the number of capturing parentheses in the pattern.

       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 pattern characters in hexadecimal

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

	 /ab 32	59/hex

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

	 /ab "literal" 32/hex

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

   Specifying the pattern's length

       By default, patterns are	passed to the compiling	functions as zero-ter-
       minated strings but can be passed by length instead of being  zero-ter-
       minated.	 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 ze-
       ros.

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

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

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

   Generating long repetitive patterns

       Some  tests use long patterns that are very repetitive. Instead of 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. The	expand and hex
       modifiers are mutually exclusive.

       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 op-
       tionally	 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 in-
       compatible 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 pat-
       tern 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  er-
       ror.   The  default  for	 the  library  is set when PCRE2 is built, but
       pcre2test sets its own default of 220, which is	required  for  running
       the standard test suite.

   Limiting the	pattern	length

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

   Using the POSIX wrapper API

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

       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  be-
       low. 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  de-
       fault, but if the use_length or hex modifiers are set, the REG_PEND ex-
       tension is used to pass it by length.

   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, 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 ta-
       bles 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

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

   Setting certain match controls

       The following modifiers are really subject modifiers, and are described
       under "Subject Modifiers" below.	However, they may  be  included	 in  a
       pattern's  modifier  list, in which case	they are applied to every sub-
       ject 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
	     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_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

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

   Specifying literal subject lines

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

   Saving a compiled pattern

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

   Testing foreign pattern conversion

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

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

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

       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  process-
       ing, overriding the defaults, which are operating-system	dependent.

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

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

       If the posix or posix_nosub modifier was	present	on the pattern,	 caus-
       ing the POSIX wrapper API to be used, the only option-setting modifiers
       that have any effect are	notbol,	notempty, and noteol, causing REG_NOT-
       BOL,  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	 wrap-
       per. It is ignored (with	a warning) if used for non-POSIX matching.

	     posix_startend=<n>[:<m>]

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

   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
	     allvector			show the entire	ovector
	     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_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 match and depth limits
	     get=<number or name>	extract	captured substring
	     getall			extract	all captured substrings
	 /g  global			global matching
	     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
	     offset=<n>			set starting offset
	     offset_limit=<n>		set offset limit
	     ovector=<n>		set size of output vector
	     recursion_limit=<n>	obsolete synonym for depth_limit
	     replace=<string>		specify	a replacement string
	     startchar			show startchar when relevant
	     startoffset=<n>		same as	offset=<n>
	     substitute_callout		use substitution callouts
	     substitute_extedded	use PCRE2_SUBSTITUTE_EXTENDED
	     substitute_literal		use PCRE2_SUBSTITUTE_LITERAL
	     substitute_matched		use PCRE2_SUBSTITUTE_MATCHED
	     substitute_overflow_length	use 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 effects of these modifiers are described in the following sections.
       When matching via the POSIX wrapper API,	the  aftertext,	 allaftertext,
       and  ovector subject modifiers work as described	below. All other modi-
       fiers are either	ignored, with a	warning	message, or cause an error.

   Showing more	text

       The aftertext modifier requests that as well as outputting the part  of
       the subject string that matched the entire pattern, pcre2test should in
       addition	output the remainder of	the subject string. This is useful for
       tests where the subject contains	multiple copies	of the same substring.
       The allaftertext	modifier requests the same action  for	captured  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,
       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 look-
       behind 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  out-
       put by '<' or '>' characters underneath them.  Here is an example:

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

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

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

	   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>". 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.

   Showing the entire ovector, for all outcomes

       The allvector modifier requests that the	entire ovector be shown, what-
       ever 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  af-
       ter  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,	 "<un-
       changed>"  is  output.  After  a	 successful match, this	applies	to all
       groups after the	maximum	capture	group for the pattern. In other	 cases
       it  applies to the entire ovector. After	a partial match, the first two
       elements	are the	only ones that should be set. After a DFA  match,  the
       amount  of  ovector  that is used depends on the	number of matches that
       were found.

   Testing pattern callouts

       A callout function is supplied when pcre2test calls the library	match-
       ing  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  decribed	separately  in
       "Testing	the substitution function" below.

   Finding all matches in a string

       Searching for all possible matches within a subject can be requested by
       the global or altglobal modifier. After finding a match,	 the  matching
       function	 is  called  again to search the remainder of the subject. The
       difference between global and altglobal is that	the  former  uses  the
       start_offset  argument  to  pcre2_match() or pcre2_dfa_match() to start
       searching at a new point	within the entire string (which	is  what  Perl
       does), whereas the latter passes	over a shortened subject. This makes a
       difference to the matching process if the pattern begins	with a 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  re-
       tried.  This imitates the way Perl handles such cases when using	the /g
       modifier	or the split() function. Normally, the	start  offset  is  ad-
       vanced  by one character, but if	the newline convention recognizes CRLF
       as a newline, and the current character is CR followed by  LF,  an  ad-
       vance 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 capture group name or num-
       ber, 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 (or after one call of
       pcre2_match() in	the case of PCRE2_SUBSTITUTE_MATCHED). Note  that  re-
       placement  strings cannot contain commas, because a comma signifies the
       end of a	modifier. This is not thought to be an issue in	 a  test  pro-
       gram.

       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_literal	     PCRE2_SUBSTITUTE_LITERAL
	 substitute_matched	     PCRE2_SUBSTITUTE_MATCHED
	 substitute_overflow_length  PCRE2_SUBSTITUTE_OVERFLOW_LENGTH
	 substitute_replacement_only PCRE2_SUBSTITUTE_REPLACEMENT_ONLY
	 substitute_unknown_unset    PCRE2_SUBSTITUTE_UNKNOWN_UNSET
	 substitute_unset_empty	     PCRE2_SUBSTITUTE_UNSET_EMPTY

       See the pcre2api	documentation for details of these options.

       After  a	 successful  substitution, the modified	string is output, 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 re-
       placement 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_ER-
       ROR_NOMEMORY when the output buffer  is	too  small.  However,  if  the
       PCRE2_SUBSTITUTE_OVERFLOW_LENGTH	 option	 is  set (by using the substi-
       tute_overflow_length  modifier),	 pcre2_substitute()  continues	to  go
       through	the  motions  of  matching and substituting (but not doing any
       callouts), in order to compute the size of  buffer  that	 is  required.
       When  this  happens,  pcre2test shows the required buffer length	(which
       includes	space for the trailing zero) as	part of	the error message. For
       example:

	 /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().

   Testing substitute callouts

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

	 /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

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

       By  default,  the substitution callout function returns zero, which ac-
       cepts the replacement and causes	matching to continue if	/g  was	 used.
       Two  further modifiers can be used to test other	return values. If sub-
       stitute_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, substi-
       tute_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 both are set for the same number, stop takes precedence. Only	a sin-
       gle skip	or stop	is supported, which is sufficient for testing that the
       feature works.

   Setting the JIT stack size

       The jitstack modifier provides a	way of setting the maximum stack  size
       that  is	 used  by the just-in-time optimization	code. It is ignored if
       JIT optimization	is not being used. The value is	a number of  kibibytes
       (units  of  1024	 bytes). Setting zero reverts to the default of	32KiB.
       Providing a stack that is larger	than the default is necessary only for
       very  complicated  patterns.  If	 jitstack is set non-zero on a subject
       line it overrides any value that	was set	on the pattern.

   Setting heap, match,	and depth limits

       The heap_limit, match_limit, and	depth_limit modifiers set  the	appro-
       priate  limits  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 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
       minimum values for each parameter that allows  the  match  to  complete
       without error. If JIT is	being used, only the match limit is relevant.

       When using this modifier, the pattern should not	contain	any limit set-
       tings 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 func-
       tion, 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. A value of	zero disables the use of any heap memory; many
       simple pattern matches can be done without using	the heap, so  zero  is
       not an unreasonable setting.

   Showing MARK	names

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

   Showing memory usage

       The  memory modifier causes pcre2test to	log the	sizes of all heap mem-
       ory  allocation	and  freeing  calls  that  occur  during  a  call   to
       pcre2_match()  or  pcre2_dfa_match(). These occur only when a match re-
       quires a	bigger vector than the default	for  remembering  backtracking
       points  (pcre2_match())	or for internal	workspace (pcre2_dfa_match()).
       In many cases there will	be no heap memory used and therefore no	 addi-
       tional output. No heap memory is	allocated during matching with JIT, so
       in that case the	memory modifier	never has any effect. For  this	 modi-
       fier  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.

   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 ap-
       pears, though of	course it can also be used to set a default in a #sub-
       ject  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 is ignored, with a warning.

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

   Passing a NULL context

       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 or substitute_callout modifiers.

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_ER-
       ROR_NOMATCH, or "Partial	match:"	followed  by  the  partially  matching
       substring  when	the  return is PCRE2_ERROR_PARTIAL. (Note that this is
       the entire substring that was inspected during the  partial  match;  it
       may  include  characters	 before	the actual match start if a lookbehind
       assertion, \K, \b, or \B	was involved.)

       For any other return, pcre2test outputs the PCRE2 negative error	number
       and  a  short  descriptive  phrase. If the error	is a failed UTF	string
       check, the code unit offset of the start	of the	failing	 character  is
       also output. Here is an example of an interactive pcre2test run.

	 $ pcre2test
	 PCRE2 version 10.22 2016-07-29

	   re> /^abc(\d+)/
	 data> abc123
	  0: abc123
	  1: 123
	 data> xyz
	 No match

       Unset capturing substrings that are not followed	by one that is set are
       not shown by pcre2test unless the allcaptures modifier is specified. In
       the following example, there are	two capturing substrings, but when the
       first data line is matched, the second, unset substring is  not	shown.
       An  "internal" unset substring is shown as "<unset>", as	for the	second
       data line.

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

       If the strings contain any non-printing characters, they	are output  as
       \xhh  escapes  if  the  value is	less than 256 and UTF mode is not set.
       Otherwise they are output as \x{hh...} escapes. See below for the 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 at-
       tempts 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).  Af-
       ter  a PCRE2_ERROR_PARTIAL return, the output is	"Partial match:", fol-
       lowed by	the partially matching substring. Note that this is the	entire
       substring  that	was inspected during the partial match;	it may include
       characters before the actual match start	if a lookbehind	assertion, \b,
       or \B was involved. (\K is not supported	for DFA	matching.)

       If global matching is requested,	the search for further matches resumes
       at the end of the longest match.	For example:

	   re> /(tang|tangerine|tan)/g
	 data> yellow tangerine	and tangy sultana\=dfa
	  0: tangerine
	  1: tang
	  2: tan
	  0: tang
	  1: tan
	  0: tan

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

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\=ps,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, and with JIT, though	there are some
       differences  in behaviour. The output for callouts with numerical argu-
       ments 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  at-
       tempt  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 posi-
       tions are the same, or if the current position precedes the start posi-
       tion, which can happen if the callout is	in a lookbehind	assertion.

       Callouts	numbered 255 are assumed to be automatic callouts, inserted as
       a result	of the auto_callout pattern modifier. In this case, instead of
       showing	the  callout  number, the offset in the	pattern, preceded by a
       plus, is	output.	For example:

	   re> /\d?[A-E]\*/auto_callout
	 data> E*
	 --->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 ex-
       ample:

	   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 be-
       fore 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

   Callout modifiers

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

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

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

       When using the interpretive  matching  function	pcre2_match()  without
       JIT,  setting  the callout_extra	modifier causes	additional output from
       pcre2test's callout function to be generated. For the first callout  in
       a  match	 attempt at a new starting position in the subject, "New match
       attempt"	is output. If there has	been a backtrack since the last	 call-
       out (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

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

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

   Return values from callouts

       The default return from the callout  function  is  zero,	 which	allows
       matching	to continue. The callout_fail modifier can be given one	or two
       numbers.	If there is only one number, 1 is returned instead of 0	(caus-
       ing 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, caus-
       ing  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  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.

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

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  is-
       print() function	is used	to distinguish printing	and non-printing char-
       acters.

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 ta-
       bles. 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 se-
       rializing 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  com-
       piled,  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  im-
       mediate	matching.  By using push and/or	pushcopy, a number of patterns
       can be compiled and retained. These  modifiers  are  incompatible  with
       posix, and control modifiers that act at	match time are ignored (with a
       message)	for the	stacked	patterns. The jitverify	modifier applies  only
       at compile time.

       The command

	 #save <filename>

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

	 #load <filename>

       reads  the  data	in the file, and then arranges for it to be de-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, posix_nosub, push, and  pushcopy	 are  not  al-
       lowed,  nor  are	 any option-setting modifiers.	The JIT	modifiers are,
       however permitted. Here is an example that saves	and reloads  two  pat-
       terns.

	 /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.

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

SEE ALSO

       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: 20	March 2020
       Copyright (c) 1997-2020 University of Cambridge.

PCRE 10.35			 20 March 2020			  PCRE2TEST(1)

NAME | 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

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