pcre2/doc/pcre2test.1

.TH PCRE2TEST 1 "16 June 2017" "PCRE 10.30"
.SH NAME
pcre2test - a program for testing Perl-compatible regular expressions.
.SH SYNOPSIS
.rs
.sp
.B pcre2test "[options] [input file [output file]]"
.sp
\fBpcre2test\fP 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
.\" HREF
\fBpcre2pattern\fP
.\"
documentation. For details of the PCRE2 library function calls and their
options, see the
.\" HREF
\fBpcre2api\fP
.\"
documentation.
.P
The input for \fBpcre2test\fP is a sequence of regular expression patterns and
subject strings to be matched. There are also command lines for setting
defaults and controlling some special actions. The output shows the result of
each match attempt. Modifiers on external or internal command lines, the
patterns, and the subject lines specify PCRE2 function options, control how the
subject is processed, and what output is produced.
.P
As the original fairly simple PCRE library evolved, it acquired many different
features, and as a result, the original \fBpcretest\fP 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 \fBpcre2test\fP, 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.
.
.
.SH "PCRE2's 8-BIT, 16-BIT AND 32-BIT LIBRARIES"
.rs
.sp
Different versions of the PCRE2 library can be built to support character
strings that are encoded in 8-bit, 16-bit, or 32-bit code units. One, two, or
all three of these libraries may be simultaneously installed. The
\fBpcre2test\fP program can be used to test all the libraries. However, its own
input and output are always in 8-bit format. When testing the 16-bit or 32-bit
libraries, patterns and subject strings are converted to 16-bit or 32-bit
format before being passed to the library functions. Results are converted back
to 8-bit code units for output.
.P
In the rest of this document, the names of library functions and structures
are given in generic form, for example, \fBpcre_compile()\fP. The actual
names used in the libraries have a suffix _8, _16, or _32, as appropriate.
.
.
.\" HTML <a name="inputencoding"></a>
.SH "INPUT ENCODING"
.rs
.sp
Input to \fBpcre2test\fP is processed line by line, either by calling the C
library's \fBfgets()\fP function, or via the \fBlibreadline\fP 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.
.P
The input is processed using using C's string functions, so must not
contain binary zeros, even though in Unix-like environments, \fBfgets()\fP
treats any bytes other than newline as data characters. An error is generated
if a binary zero is encountered. By default subject lines are processed for
backslash escapes, which makes it possible to include any data value in strings
that are passed to the library for matching. For patterns, there is a facility
for specifying some or all of the 8-bit input characters as hexadecimal pairs,
which makes it possible to include binary zeros.
.
.
.SS "Input for the 16-bit and 32-bit libraries"
.rs
.sp
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 \fButf\fP modifier (see
.\" HTML <a href="#optionmodifiers">
.\" </a>
"Setting compilation options"
.\"
below) is set, the pattern and any following subject lines are interpreted as
UTF-8 strings and translated to UTF-16 or UTF-32 as appropriate.
.P
For non-UTF testing of wide characters, the \fButf8_input\fP modifier can be
used. This is mutually exclusive with \fButf\fP, and is allowed only in 16-bit
or 32-bit mode. It causes the pattern and following subject lines to be treated
as UTF-8 according to the original definition (RFC 2279), which allows for
character values up to 0x7fffffff. Each character is placed in one 16-bit or
32-bit code unit (in the 16-bit case, values greater than 0xffff cause an error
to occur).
.P
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 \fButf8_input\fP set, if any
character is preceded by the byte 0xff (which is an illegal 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.
.
.
.SH "COMMAND LINE OPTIONS"
.rs
.TP 10
\fB-8\fP
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.
.TP 10
\fB-16\fP
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.
.TP 10
\fB-32\fP
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.
.TP 10
\fB-ac\fP
Behave as if each pattern has the \fBauto_callout\fP modifier, that is, insert
automatic callouts into every pattern that is compiled.
.TP 10
\fB-b\fP
Behave as if each pattern has the \fBfullbincode\fP modifier; the full
internal binary form of the pattern is output after compilation.
.TP 10
\fB-C\fP
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.
.TP 10
\fB-C\fP \fIoption\fP
Output information about a specific build-time option, then exit. This
functionality is intended for use in scripts such as \fBRunTest\fP. The
following options output the value and set the exit code as indicated:
.sp
  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 \eR matches:
               ANYCRLF or ANY
               exit code is always 0
.sp
The following options output 1 for true or 0 for false, and set the exit code
to the same value:
.sp
  backslash-C  \eC 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
.sp
If an unknown option is given, an error message is output; the exit code is 0.
.TP 10
\fB-d\fP
Behave as if each pattern has the \fBdebug\fP modifier; the internal
form and information about the compiled pattern is output after compilation;
\fB-d\fP is equivalent to \fB-b -i\fP.
.TP 10
\fB-dfa\fP
Behave as if each subject line has the \fBdfa\fP modifier; matching is done
using the \fBpcre2_dfa_match()\fP function instead of the default
\fBpcre2_match()\fP.
.TP 10
\fB-error\fP \fInumber[,number,...]\fP
Call \fBpcre2_get_error_message()\fP 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.
.TP 10
\fB-help\fP
Output a brief summary these options and then exit.
.TP 10
\fB-i\fP
Behave as if each pattern has the \fBinfo\fP modifier; information about the
compiled pattern is given after compilation.
.TP 10
\fB-jit\fP
Behave as if each pattern line has the \fBjit\fP modifier; after successful
compilation, each pattern is passed to the just-in-time compiler, if available.
.TP 10
\fB-jitverify\fP
Behave as if each pattern line has the \fBjitverify\fP modifier; after
successful compilation, each pattern is passed to the just-in-time compiler, if
available, and the use of JIT is verified.
.TP 10
\fB-pattern\fB \fImodifier-list\fP
Behave as if each pattern line contains the given modifiers.
.TP 10
\fB-q\fP
Do not output the version number of \fBpcre2test\fP at the start of execution.
.TP 10
\fB-S\fP \fIsize\fP
On Unix-like systems, set the size of the run-time stack to \fIsize\fP
megabytes.
.TP 10
\fB-subject\fP \fImodifier-list\fP
Behave as if each subject line contains the given modifiers.
.TP 10
\fB-t\fP
Run each compile and match many times with a timer, and output the resulting
times per compile or match. When JIT is used, separate times are given for the
initial compile and the JIT compile. You can control the number of iterations
that are used for timing by following \fB-t\fP 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.
.TP 10
\fB-tm\fP
This is like \fB-t\fP except that it times only the matching phase, not the
compile phase.
.TP 10
\fB-T\fP \fB-TM\fP
These behave like \fB-t\fP and \fB-tm\fP, but in addition, at the end of a run,
the total times for all compiles and matches are output.
.TP 10
\fB-version\fP
Output the PCRE2 version number and then exit.
.
.
.SH "DESCRIPTION"
.rs
.sp
If \fBpcre2test\fP 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 \fBpcre2test\fP is given only one argument, it reads from
that file and writes to stdout. Otherwise, it reads from stdin and writes to
stdout.
.P
When \fBpcre2test\fP is built, a configuration option can specify that it
should be linked with the \fBlibreadline\fP or \fBlibedit\fP library. When this
is done, if the input is from a terminal, it is read using the \fBreadline()\fP
function. This provides line-editing and history facilities. The output from
the \fB-help\fP option states whether or not \fBreadline()\fP will be used.
.P
The program handles any number of tests, each of which consists of a set of
input lines. Each set starts with a regular expression pattern, followed by any
number of subject lines to be matched against that pattern. In between sets of
test data, command lines that begin with # may appear. This file format, with
some restrictions, can also be processed by the \fBperltest.sh\fP script that
is distributed with PCRE2 as a means of checking that the behaviour of PCRE2
and Perl is the same.
.P
When the input is a terminal, \fBpcre2test\fP 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.
.P
Each subject line is matched separately and independently. If you want to do
multi-line matches, you have to use the \en escape sequence (or \er or \er\en,
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.
.P
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.
.
.
.SH "COMMAND LINES"
.rs
.sp
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:
.sp
  #forbid_utf
.sp
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 \eP, \ep, or \eX,
which are still supported when PCRE2_UTF is not set, but which require Unicode
property support to be included in the library.
.P
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 \fB#pattern\fP;
the difference is that \fB#forbid_utf\fP cannot be unset, and the automatic
options are not displayed in pattern information, to avoid cluttering up test
output.
.sp
  #load <filename>
.sp
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"
.\" HTML <a href="#saverestore">
.\" </a>
below.
.\"
.sp
  #newline_default [<newline-list>]
.sp
When PCRE2 is built, a default newline convention can be specified. This
determines which characters and/or character pairs are recognized as indicating
a newline in a pattern or subject string. The default can be overridden when a
pattern is compiled. The standard test files contain tests of various newline
conventions, but the majority of the tests expect a single linefeed to be
recognized as a newline by default. Without special action the tests would fail
when PCRE2 is compiled with either CR or CRLF as the default newline.
.P
The #newline_default command specifies a list of newline types that are
acceptable as the default. The types must be one of CR, LF, CRLF, ANYCRLF,
ANY, or NUL (in upper or lower case), for example:
.sp
  #newline_default LF Any anyCRLF
.sp
If the default newline is in the list, this command has no effect. Otherwise,
except when testing the POSIX API, a \fBnewline\fP 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 \fBnewline\fP 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.
.P
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 \fBposix\fP or \fBposix_nosub\fP
modifier is used when \fB#newline_default\fP would set a default for the
non-POSIX API.
.sp
  #pattern <modifier-list>
.sp
This command sets a default modifier list that applies to all subsequent
patterns. Modifiers on a pattern can change these settings.
.sp
  #perltest
.sp
The appearance of this line causes all subsequent modifier settings to be
checked for compatibility with the \fBperltest.sh\fP 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 \fBpcre2test\fP, and should not be used in
test files that are also processed by \fBperltest.sh\fP. The \fB#perltest\fP
command helps detect tests that are accidentally put in the wrong file.
.sp
  #pop [<modifiers>]
  #popcopy [<modifiers>]
.sp
These commands are used to manipulate the stack of compiled patterns, as
described in the section entitled "Saving and restoring compiled patterns"
.\" HTML <a href="#saverestore">
.\" </a>
below.
.\"
.sp
  #save <filename>
.sp
This command is used to save a set of compiled patterns to a file, as described
in the section entitled "Saving and restoring compiled patterns"
.\" HTML <a href="#saverestore">
.\" </a>
below.
.\"
.sp
  #subject <modifier-list>
.sp
This command sets a default modifier list that applies to all subsequent
subject lines. Modifiers on a subject line can change these settings.
.
.
.SH "MODIFIER SYNTAX"
.rs
.sp
Modifier lists are used with both pattern and subject lines. Items in a list
are separated by commas followed by optional white space. Trailing whitespace
in a modifier list is ignored. Some modifiers may be given for both patterns
and subject lines, whereas others are valid only for one or the other. Each
modifier has a long name, for example "anchored", and some of them must be
followed by an equals sign and a value, for example, "offset=12". Values cannot
contain comma characters, but may contain spaces. Modifiers that do not take
values may be preceded by a minus sign to turn off a previous setting.
.P
A few of the more common modifiers can also be specified as single letters, for
example "i" for "caseless". In documentation, following the Perl convention,
these are written with a slash ("the /i modifier") for clarity. Abbreviated
modifiers must all be concatenated in the first item of a modifier list. If the
first item is not recognized as a long modifier name, it is interpreted as a
sequence of these abbreviations. For example:
.sp
  /abc/ig,newline=cr,jit=3
.sp
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.
.
.
.SH "PATTERN SYNTAX"
.rs
.sp
A pattern line must start with one of the following characters (common symbols,
excluding pattern meta-characters):
.sp
  / ! " ' ` - = _ : ; , % & @ ~
.sp
This is interpreted as the pattern's delimiter. A regular expression may be
continued over several input lines, in which case the newline characters are
included within it. It is possible to include the delimiter within the pattern
by escaping it with a backslash, for example
.sp
  /abc\e/def/
.sp
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 followed by a
backslash, for example,
.sp
  /abc/\e
.sp
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
.sp
  /abc\e/
.sp
is interpreted as the first line of a pattern that starts with "abc/", causing
pcre2test to read the next line as a continuation of the regular expression.
.P
A pattern can be followed by a modifier list (details below).
.
.
.SH "SUBJECT LINE SYNTAX"
.rs
.sp
Before each subject line is passed to \fBpcre2_match()\fP or
\fBpcre2_dfa_match()\fP, leading and trailing white space is removed, and the
line is scanned for backslash escapes, unless the \fBsubject_literal\fP
modifier was set for the pattern. The following provide a means of encoding
non-printing characters in a visible way:
.sp
  \ea         alarm (BEL, \ex07)
  \eb         backspace (\ex08)
  \ee         escape (\ex27)
  \ef         form feed (\ex0c)
  \en         newline (\ex0a)
  \er         carriage return (\ex0d)
  \et         tab (\ex09)
  \ev         vertical tab (\ex0b)
  \ennn       octal character (up to 3 octal digits); always
               a byte unless > 255 in UTF-8 or 16-bit or 32-bit mode
  \eo{dd...}  octal character (any number of octal digits}
  \exhh       hexadecimal byte (up to 2 hex digits)
  \ex{hh...}  hexadecimal character (any number of hex digits)
.sp
The use of \ex{hh...} is not dependent on the use of the \fButf\fP modifier on
the pattern. It is recognized always. There may be any number of hexadecimal
digits inside the braces; invalid values provoke error messages.
.P
Note that \exhh 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, \ex{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, \ex{hh} generates one byte
for values less than 256, and causes an error for greater values.
.P
In UTF-16 mode, all 4-digit \ex{hhhh} values are accepted. This makes it
possible to construct invalid UTF-16 sequences for testing purposes.
.P
In UTF-32 mode, all 4- to 8-digit \ex{...} values are accepted. This makes it
possible to construct invalid UTF-32 sequences for testing purposes.
.P
There is a special backslash sequence that specifies replication of one or more
characters:
.sp
  \e[<characters>]{<count>}
.sp
This makes it possible to test long strings without having to provide them as
part of the file. For example:
.sp
  \e[abc]{4}
.sp
is converted to "abcabcabcabc". This feature does not support nesting. To
include a closing square bracket in the characters, code it as \ex5D.
.P
A backslash followed by an equals sign marks the end of the subject string and
the start of a modifier list. For example:
.sp
  abc\e=notbol,notempty
.sp
If the subject string is empty and \e= is followed by whitespace, the line is
treated as a comment line, and is not used for matching. For example:
.sp
  \e= This is a comment.
  abc\e= This is an invalid modifier list.
.sp
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.
.P
If the \fBsubject_literal\fP modifier is set for a pattern, all subject lines
that follow are treated as literals, with no special treatment of backslashes.
No replication is possible, and any subject modifiers must be set as defaults
by a \fB#subject\fP command.
.
.
.SH "PATTERN MODIFIERS"
.rs
.sp
There are several types of modifier that can appear in pattern lines. Except
where noted below, they may also be used in \fB#pattern\fP commands. A
pattern's modifier list can add to or override default modifiers that were set
by a previous \fB#pattern\fP command.
.
.
.\" HTML <a name="optionmodifiers"></a>
.SS "Setting compilation options"
.rs
.sp
The following modifiers set options for \fBpcre2_compile()\fP. 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 abbreviations that are the same as
Perl options. There is special handling for /x: if a second x is present,
PCRE2_EXTENDED is converted into PCRE2_EXTENDED_MORE as in Perl. A third
appearance adds PCRE2_EXTENDED as well, though this makes no difference to the
way \fBpcre2_compile()\fP behaves. See
.\" HREF
\fBpcre2api\fP
.\"
for a description of the effects of these options.
.sp
      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
  /x  extended                  set PCRE2_EXTENDED
  /xx extended_more             set PCRE2_EXTENDED_MORE 
      firstline                 set PCRE2_FIRSTLINE
      literal                   set PCRE2_LITERAL 
      match_line                set PCRE2_EXTRA_MATCH_LINE 
      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
.sp
As well as turning on the PCRE2_UTF option, the \fButf\fP modifier causes all
non-printing characters in output strings to be printed using the \ex{hh...}
notation. Otherwise, those less than 0x100 are output in hex without the curly
brackets. Setting \fButf\fP 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.
.
.
.\" HTML <a name="controlmodifiers"></a>
.SS "Setting compilation controls"
.rs
.sp
The following modifiers affect the compilation process or request information
about the pattern. There are single-letter abbreviations for some that are
heavily used in the test files.
.sp
      bsr=[anycrlf|unicode]     specify \eR handling
  /B  bincode                   show binary code without lengths
      callout_info              show callout information
      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]            select internal tables
      use_length                do not zero-terminate the pattern
      utf8_input                treat input as UTF-8
.sp
The effects of these modifiers are described in the following sections.
.
.
.SS "Newline and \eR handling"
.rs
.sp
The \fBbsr\fP modifier specifies what \eR in a pattern should match. If it is
set to "anycrlf", \eR matches CR, LF, or CRLF only. If it is set to "unicode",
\eR matches any Unicode newline sequence. The default is specified when PCRE2
is built, with the default default being Unicode.
.P
The \fBnewline\fP 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).
.
.
.SS "Information about a pattern"
.rs
.sp
The \fBdebug\fP modifier is a shorthand for \fBinfo,fullbincode\fP, requesting
all available information.
.P
The \fBbincode\fP modifier causes a representation of the compiled code to be
output after compilation. This information does not contain length and offset
values, which ensures that the same output is generated for different internal
link sizes and different code unit widths. By using \fBbincode\fP, the same
regression tests can be used in different environments.
.P
The \fBfullbincode\fP modifier, by contrast, \fIdoes\fP 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.
.P
The \fBinfo\fP 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 \fBpcre2_pattern_info()\fP function. Here are
some typical examples:
.sp
    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
.sp
    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
.sp
"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.
.P
The \fBframesize\fP modifier shows the size, in bytes, of the storage frames 
used by \fBpcre2_match()\fP for handling backtracking. The size depends on the
number of capturing parentheses in the pattern.
.P
The \fBcallout_info\fP modifier requests information about all the callouts in
the pattern. A list of them is output at the end of any other information that
is requested. For each callout, either its number or string is given, followed
by the item that follows it in the pattern.
.
.
.SS "Passing a NULL context"
.rs
.sp
Normally, \fBpcre2test\fP passes a context block to \fBpcre2_compile()\fP. If
the \fBnull_context\fP modifier is set, however, NULL is passed. This is for
testing that \fBpcre2_compile()\fP behaves correctly in this case (it uses
default values).
.
.
.SS "Specifying pattern characters in hexadecimal"
.rs
.sp
The \fBhex\fP modifier specifies that the characters of the pattern, except for
substrings enclosed in single or double quotes, are to be interpreted as pairs
of hexadecimal digits. This feature is provided as a way of creating patterns
that contain binary zeros and other non-printing characters. White space is
permitted between pairs of digits. For example, this pattern contains three
characters:
.sp
  /ab 32 59/hex
.sp
Parts of such a pattern are taken literally if quoted. This pattern contains
nine characters, only two of which are specified in hexadecimal:
.sp
  /ab "literal" 32/hex
.sp
Either single or double quotes may be used. There is no way of including
the delimiter within a substring. The \fBhex\fP and \fBexpand\fP modifiers are
mutually exclusive.
.
.
.SS "Specifying the pattern's length"
.rs
.sp
By default, patterns are passed to the compiling functions as zero-terminated
strings but can be passed by length instead of being zero-terminated. The
\fBuse_length\fP modifier causes this to happen. Using a length happens
automatically (whether or not \fBuse_length\fP is set) when \fBhex\fP is set,
because patterns specified in hexadecimal may contain binary zeros.
.P
If \fBhex\fP or \fBuse_length\fP is used with the POSIX wrapper API (see
.\" HTML <a href="#posixwrapper">
.\" </a>
"Using the POSIX wrapper API"
.\"
below), the REG_PEND extension is used to pass the pattern's length.
.
.
.SS "Specifying wide characters in 16-bit and 32-bit modes"
.rs
.sp
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 \fButf\fP modifier is set. For testing
the 16-bit and 32-bit libraries in non-UTF mode, the \fButf8_input\fP modifier
can be used. It is mutually exclusive with \fButf\fP. Input lines are
interpreted as UTF-8 as a means of specifying wide characters. More details are
given in
.\" HTML <a href="#inputencoding">
.\" </a>
"Input encoding"
.\"
above.
.
.
.SS "Generating long repetitive patterns"
.rs
.sp
Some tests use long patterns that are very repetitive. Instead of creating a
very long input line for such a pattern, you can use a special repetition
feature, similar to the one described for subject lines above. If the
\fBexpand\fP modifier is present on a pattern, parts of the pattern that have
the form
.sp
  \e[<characters>]{<count>}
.sp
are expanded before the pattern is passed to \fBpcre2_compile()\fP. For
example, \e[AB]{6000} is expanded to "ABAB..." 6000 times. This construction
cannot be nested. An initial "\e[" 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 \fBexpand\fP and \fBhex\fP modifiers are
mutually exclusive.
.P
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, \e[AB]{6000,6000} is not recognized as an
expansion item.
.P
If the \fBinfo\fP modifier is set on an expanded pattern, the result of the
expansion is included in the information that is output.
.
.
.SS "JIT compilation"
.rs
.sp
Just-in-time (JIT) compiling is a heavyweight optimization that can greatly
speed up pattern matching. See the
.\" HREF
\fBpcre2jit\fP
.\"
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 \fBpartial\fP
modifier in "Subject Modifiers"
.\" HTML <a href="#subjectmodifiers">
.\" </a>
below
.\"
for details of how these options are specified for each match attempt.
.P
JIT compilation is requested by the \fBjit\fP 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:
.sp
  1  compile JIT code for non-partial matching
  2  compile JIT code for soft partial matching
  4  compile JIT code for hard partial matching
.sp
The possible values for the \fBjit\fP modifier are therefore:
.sp
  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
.sp
If no number is given, 7 is assumed. The phrase "partial matching" means a call
to \fBpcre2_match()\fP with either the PCRE2_PARTIAL_SOFT or the
PCRE2_PARTIAL_HARD option set. Note that such a call may return a complete
match; the options enable the possibility of a partial match, but do not
require it. Note also that if you request JIT compilation only for partial
matching (for example, jit=2) but do not set the \fBpartial\fP modifier on a
subject line, that match will not use JIT code because none was compiled for
non-partial matching.
.P
If JIT compilation is successful, the compiled JIT code will automatically be
used when an appropriate type of match is run, except when incompatible
run-time options are specified. For more details, see the
.\" HREF
\fBpcre2jit\fP
.\"
documentation. See also the \fBjitstack\fP modifier below for a way of
setting the size of the JIT stack.
.P
If the \fBjitfast\fP modifier is specified, matching is done using the JIT
"fast path" interface, \fBpcre2_jit_match()\fP, which skips some of the sanity
checks that are done by \fBpcre2_match()\fP, and of course does not work when
JIT is not supported. If \fBjitfast\fP is specified without \fBjit\fP, jit=7 is
assumed.
.P
If the \fBjitverify\fP modifier is specified, information about the compiled
pattern shows whether JIT compilation was or was not successful. If
\fBjitverify\fP is specified without \fBjit\fP, jit=7 is assumed. If JIT
compilation is successful when \fBjitverify\fP 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.
.
.
.SS "Setting a locale"
.rs
.sp
The \fBlocale\fP modifier must specify the name of a locale, for example:
.sp
  /pattern/locale=fr_FR
.sp
The given locale is set, \fBpcre2_maketables()\fP is called to build a set of
character tables for the locale, and this is then passed to
\fBpcre2_compile()\fP when compiling the regular expression. The same tables
are used when matching the following subject lines. The \fBlocale\fP modifier
applies only to the pattern on which it appears, but can be given in a
\fB#pattern\fP command if a default is needed. Setting a locale and alternate
character tables are mutually exclusive.
.
.
.SS "Showing pattern memory"
.rs
.sp
The \fBmemory\fP 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
\fBpcre2_code\fP 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:
.sp
    re> /a(b)c/jit,memory
  Memory allocation (code space): 21
  Memory allocation (JIT code): 1910
.sp
.
.
.SS "Limiting nested parentheses"
.rs
.sp
The \fBparens_nest_limit\fP 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 \fBpcre2test\fP
sets its own default of 220, which is required for running the standard test
suite.
.
.
.SS "Limiting the pattern length"
.rs
.sp
The \fBmax_pattern_length\fP modifier sets a limit, in code units, to the
length of pattern that \fBpcre2_compile()\fP will accept. Breaching the limit
causes a compilation error. The default is the largest number a PCRE2_SIZE
variable can hold (essentially unlimited).
.
.
.\" HTML <a name="posixwrapper"></a>
.SS "Using the POSIX wrapper API"
.rs
.sp
The \fBposix\fP and \fBposix_nosub\fP modifiers cause \fBpcre2test\fP to call
PCRE2 via the POSIX wrapper API rather than its native API. When
\fBposix_nosub\fP is used, the POSIX option REG_NOSUB is passed to
\fBregcomp()\fP. The POSIX wrapper supports only the 8-bit library. Note that
it does not imply POSIX matching semantics; for more detail see the
.\" HREF
\fBpcre2posix\fP
.\"
documentation. The following pattern modifiers set options for the
\fBregcomp()\fP function:
.sp
  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       )
.sp
The \fBregerror_buffsize\fP modifier specifies a size for the error buffer that
is passed to \fBregerror()\fP in the event of a compilation error. For example:
.sp
  /abc/posix,regerror_buffsize=20
.sp
This provides a means of testing the behaviour of \fBregerror()\fP when the
buffer is too small for the error message. If this modifier has not been set, a
large buffer is used.
.P
The \fBaftertext\fP and \fBallaftertext\fP subject modifiers work as described
below. All other modifiers are either ignored, with a warning message, or cause
an error.
.P
The pattern is passed to \fBregcomp()\fP as a zero-terminated string by 
default, but if the \fBuse_length\fP or \fBhex\fP modifiers are set, the 
REG_PEND extension is used to pass it by length.
.
.
.SS "Testing the stack guard feature"
.rs
.sp
The \fBstackguard\fP modifier is used to test the use of
\fBpcre2_set_compile_recursion_guard()\fP, a function that is provided to
enable stack availability to be checked during compilation (see the
.\" HREF
\fBpcre2api\fP
.\"
documentation for details). If the number specified by the modifier is greater
than zero, \fBpcre2_set_compile_recursion_guard()\fP is called to set up
callback from \fBpcre2_compile()\fP 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.
.
.
.SS "Using alternative character tables"
.rs
.sp
The value specified for the \fBtables\fP 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
\fBpcre2_compile()\fP. This is used in the PCRE2 tests to check behaviour with
different character tables. The digit specifies the tables as follows:
.sp
  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
.sp
In table 2, some characters whose codes are greater than 128 are identified as
letters, digits, spaces, etc. Setting alternate character tables and a locale
are mutually exclusive.
.
.
.SS "Setting certain match controls"
.rs
.sp
The following modifiers are really subject modifiers, and are described under 
"Subject Modifiers" below. However, they may be included in a pattern's
modifier list, in which case they are applied to every subject line that is
processed with that pattern. They may not appear in \fB#pattern\fP commands.
These modifiers do not affect the compilation process.
.sp
      aftertext                  show text after match
      allaftertext               show text after captures
      allcaptures                show all captures
      allusedtext                show all consulted text
  /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_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
.sp
These modifiers may not appear in a \fB#pattern\fP command. If you want them as
defaults, set them in a \fB#subject\fP command.
.
.
.SS "Specifying literal subject lines"
.rs
.sp
If the \fBsubject_literal\fP modifier is present on a pattern, all the subject 
lines that it matches are taken as literal strings, with no interpretation of 
backslashes. It is not possible to set subject modifiers on such lines, but any 
that are set as defaults by a \fB#subject\fP command are recognized.
.
.
.SS "Saving a compiled pattern"
.rs
.sp
When a pattern with the \fBpush\fP modifier is successfully compiled, it is
pushed onto a stack of compiled patterns, and \fBpcre2test\fP expects the next
line to contain a new pattern (or a command) instead of a subject line. This
facility is used when saving compiled patterns to a file, as described in the
section entitled "Saving and restoring compiled patterns"
.\" HTML <a href="#saverestore">
.\" </a>
below. If \fBpushcopy\fP is used instead of \fBpush\fP, a copy of the compiled
pattern is stacked, leaving the original as current, ready to match the
following input lines. This provides a way of testing the
\fBpcre2_code_copy()\fP function.
.\"
The \fBpush\fP and \fBpushcopy \fP modifiers are incompatible with compilation
modifiers such as \fBglobal\fP that act at match time. Any that are specified
are ignored (for the stacked copy), with a warning message, except for
\fBreplace\fP, which causes an error. Note that \fBjitverify\fP, which is
allowed, does not carry through to any subsequent matching that uses a stacked
pattern.
.
.
.\" HTML <a name="subjectmodifiers"></a>
.SH "SUBJECT MODIFIERS"
.rs
.sp
The modifiers that can appear in subject lines and the \fB#subject\fP
command are of two types.
.
.
.SS "Setting match options"
.rs
.sp
The following modifiers set options for \fBpcre2_match()\fP or
\fBpcre2_dfa_match()\fP. See
.\" HREF
\fBpcreapi\fP
.\"
for a description of their effects.
.sp
      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
.sp
The partial matching modifiers are provided with abbreviations because they
appear frequently in tests.
.P
If the \fBposix\fP or \fBposix_nosub\fP modifier was present on the pattern,
causing the POSIX wrapper API to be used, the only option-setting modifiers
that have any effect are \fBnotbol\fP, \fBnotempty\fP, and \fBnoteol\fP,
causing REG_NOTBOL, REG_NOTEMPTY, and REG_NOTEOL, respectively, to be passed to
\fBregexec()\fP. The other modifiers are ignored, with a warning message.
.P
There is one additional modifier that can be used with the POSIX wrapper. It is 
ignored (with a warning) if used for non-POSIX matching.
.sp
      posix_startend=<n>[:<m>] 
.sp
This causes the subject string to be passed to \fBregexec()\fP using the
REG_STARTEND option, which uses offsets to specify which part of the string is
searched. If only one number is given, the end offset is passed as the end of
the subject string. For more detail of REG_STARTEND, see the
.\" HREF
\fBpcre2posix\fP
.\"
documentation. If the subject string contains binary zeros (coded as escapes 
such as \ex{00} because \fBpcre2test\fP does not support actual binary zeros in 
its input), you must use \fBposix_startend\fP to specify its length.
.
.
.SS "Setting match controls"
.rs
.sp
The following modifiers affect the matching process or request additional
information. Some of them may also be specified on a pattern line (see above),
in which case they apply to every subject line that is matched against that
pattern.
.sp
      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_error=<n>[:<m>]    control callout error
      callout_fail=<n>[:<m>]     control callout failure
      callout_none               do not supply a callout function
      copy=<number or name>      copy captured substring
      depth_limit=<n>            set a depth limit
      dfa                        use \fBpcre2_dfa_match()\fP
      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
      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_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
.sp
The effects of these modifiers are described in the following sections. When
matching via the POSIX wrapper API, the \fBaftertext\fP, \fBallaftertext\fP,
and \fBovector\fP subject modifiers work as described below. All other
modifiers are either ignored, with a warning message, or cause an error.
.
.
.SS "Showing more text"
.rs
.sp
The \fBaftertext\fP modifier requests that as well as outputting the part of
the subject string that matched the entire pattern, \fBpcre2test\fP 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
\fBallaftertext\fP modifier requests the same action for captured substrings as
well as the main matched substring. In each case the remainder is output on the
following line with a plus character following the capture number.
.P
The \fBallusedtext\fP 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
\eK is used in the pattern. Characters that precede or follow the start and end
of the actual match are indicated in the output by '<' or '>' characters
underneath them. Here is an example:
.sp
    re> /(?<=pqr)abc(?=xyz)/
  data> 123pqrabcxyz456\e=allusedtext
   0: pqrabcxyz
      <<<   >>>
.sp
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).
.P
The \fBstartchar\fP 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 \eK 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:
.sp
    re> /abc\eKxyz/
  data> abcxyz\e=startchar
   0: abcxyz
      ^^^
.sp
Unlike \fBallusedtext\fP, the \fBstartchar\fP modifier can be used with JIT.
However, these two modifiers are mutually exclusive.
.
.
.SS "Showing the value of all capture groups"
.rs
.sp
The \fBallcaptures\fP modifier requests that the values of all potential
captured parentheses be output after a match. By default, only those up to the
highest one actually used in the match are output (corresponding to the return
code from \fBpcre2_match()\fP). 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); it is ignored, with a warning message, if present.
.
.
.SS "Testing callouts"
.rs
.sp
A callout function is supplied when \fBpcre2test\fP calls the library matching
functions, unless \fBcallout_none\fP is specified. If \fBcallout_capture\fP is
set, the current captured groups are output when a callout occurs. The default
return from the callout function is zero, which allows matching to continue.
.P
The \fBcallout_fail\fP modifier can be given one or two numbers. If there is
only one number, 1 is returned instead of 0 (causing matching to backtrack)
when a callout of that number is reached. If two numbers (<n>:<m>) are given, 1
is returned when callout <n> is reached and there have been at least <m>
callouts. The \fBcallout_error\fP modifier is similar, except that
PCRE2_ERROR_CALLOUT is returned, causing the entire matching process to be
aborted. If both these modifiers are set for the same callout number,
\fBcallout_error\fP takes precedence.
.P
Note that callouts with string arguments are always given the number zero. See
"Callouts" below for a description of the output when a callout it taken.
.P
The \fBcallout_data\fP modifier can be given an unsigned or a negative number.
This is set as the "user data" that is passed to the matching function, and
passed back when the callout function is invoked. Any value other than zero is
used as a return from \fBpcre2test\fP's callout function.
.
.
.SS "Finding all matches in a string"
.rs
.sp
Searching for all possible matches within a subject can be requested by the
\fBglobal\fP or \fBaltglobal\fP modifier. After finding a match, the matching
function is called again to search the remainder of the subject. The difference
between \fBglobal\fP and \fBaltglobal\fP is that the former uses the
\fIstart_offset\fP argument to \fBpcre2_match()\fP or \fBpcre2_dfa_match()\fP
to start searching at a new point within the entire string (which is what Perl
does), whereas the latter passes over a shortened subject. This makes a
difference to the matching process if the pattern begins with a lookbehind
assertion (including \eb or \eB).
.P
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 \fB/g\fP modifier or
the \fBsplit()\fP 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.
.
.
.SS "Testing substring extraction functions"
.rs
.sp
The \fBcopy\fP and \fBget\fP modifiers can be used to test the
\fBpcre2_substring_copy_xxx()\fP and \fBpcre2_substring_get_xxx()\fP functions.
They can be given more than once, and each can specify a group name or number,
for example:
.sp
   abcd\e=copy=1,copy=3,get=G1
.sp
If the \fB#subject\fP command is used to set default copy and/or get lists,
these can be unset by specifying a negative number to cancel all numbered
groups and an empty name to cancel all named groups.
.P
The \fBgetall\fP modifier tests \fBpcre2_substring_list_get()\fP, which
extracts all captured substrings.
.P
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.
.
.
.SS "Testing the substitution function"
.rs
.sp
If the \fBreplace\fP modifier is set, the \fBpcre2_substitute()\fP 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.
.P
Unlike subject strings, \fBpcre2test\fP does not process replacement strings
for escape sequences. In UTF mode, a replacement string is checked to see if it
is a valid UTF-8 string. If so, it is correctly converted to a UTF string of
the appropriate code unit width. If it is not a valid UTF-8 string, the
individual code units are copied directly. This provides a means of passing an
invalid UTF-8 string for testing purposes.
.P
The following modifiers set options (in additional to the normal match options)
for \fBpcre2_substitute()\fP:
.sp
  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
.sp
.P
After a successful substitution, the modified string is output, preceded by the
number of replacements. This may be zero if there were no matches. Here is a
simple example of a substitution test:
.sp
  /abc/replace=xxx
      =abc=abc=
   1: =xxx=abc=
      =abc=abc=\e=global
   2: =xxx=xxx=
.sp
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 \fBpcre2_substitute()\fP 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:
.sp
  /abc/
      123abc123\e=replace=[10]XYZ
   1: 123XYZ123
      123abc123\e=replace=[9]XYZ
  Failed: error -47: no more memory
.sp
The default action of \fBpcre2_substitute()\fP 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
\fBsubstitute_overflow_length\fP modifier), \fBpcre2_substitute()\fP continues
to go through the motions of matching and substituting, in order to compute the
size of buffer that is required. When this happens, \fBpcre2test\fP shows the
required buffer length (which includes space for the trailing zero) as part of
the error message. For example:
.sp
  /abc/substitute_overflow_length
      123abc123\e=replace=[9]XYZ
  Failed: error -47: no more memory: 10 code units are needed
.sp
A replacement string is ignored with POSIX and DFA matching. Specifying partial
matching provokes an error return ("bad option value") from
\fBpcre2_substitute()\fP.
.
.
.SS "Setting the JIT stack size"
.rs
.sp
The \fBjitstack\fP 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. Setting
zero reverts to the default of 32K. Providing a stack that is larger than the
default is necessary only for very complicated patterns. If \fBjitstack\fP is
set non-zero on a subject line it overrides any value that was set on the 
pattern.
.
.
.SS "Setting heap, match, and depth limits"
.rs
.sp
The \fBheap_limit\fP, \fBmatch_limit\fP, and \fBdepth_limit\fP modifiers set
the appropriate limits in the match context. These values are ignored when the
\fBfind_limits\fP modifier is specified.
.
.
.SS "Finding minimum limits"
.rs
.sp
If the \fBfind_limits\fP modifier is present on a subject line, \fBpcre2test\fP
calls the relevant matching function several times, setting different values in
the match context via \fBpcre2_set_heap_limit(), \fBpcre2_set_match_limit()\fP,
or \fBpcre2_set_depth_limit()\fP until it finds the minimum values for each
parameter that allows the match to complete without error.
.P
If JIT is being used, only the match limit is relevant. If DFA matching is
being used, only the depth limit is relevant.
.P
The \fImatch_limit\fP 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. 
.P
For non-DFA matching, the minimum \fIdepth_limit\fP 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, \fIdepth_limit\fP controls the depth of
recursive calls of the internal function that is used for handling pattern
recursion, lookaround assertions, and atomic groups.
.
.
.SS "Showing MARK names"
.rs
.sp
.P
The \fBmark\fP modifier causes the names from backtracking control verbs that
are returned from calls to \fBpcre2_match()\fP to be displayed. If a mark is
returned for a match, non-match, or partial match, \fBpcre2test\fP shows it.
For a match, it is on a line by itself, tagged with "MK:". Otherwise, it
is added to the non-match message.
.
.
.SS "Showing memory usage"
.rs
.sp
The \fBmemory\fP modifier causes \fBpcre2test\fP to log the sizes of all heap
memory allocation and freeing calls that occur during a call to
\fBpcre2_match()\fP. These occur only when a match requires a bigger vector
than the default for remembering backtracking points. In many cases there will
be no heap memory used and therefore no additional output. No heap memory is
allocated during matching with \fBpcre2_dfa_match\fP or with JIT, so in those
cases the \fBmemory\fP modifier never has any effect. For this modifier to
work, the \fBnull_context\fP modifier must not be set on both the pattern and
the subject, though it can be set on one or the other.
.
.
.SS "Setting a starting offset"
.rs
.sp
The \fBoffset\fP modifier sets an offset in the subject string at which
matching starts. Its value is a number of code units, not characters.
.
.
.SS "Setting an offset limit"
.rs
.sp
The \fBoffset_limit\fP 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 \fBuse_offset_limit\fP modifier must have been set
for the pattern; if not, an error is generated.
.
.
.SS "Setting the size of the output vector"
.rs
.sp
The \fBovector\fP 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
\fB#subject\fP command. It specifies the number of pairs of offsets that are
available for storing matching information. The default is 15.
.P
A value of zero is useful when testing the POSIX API because it causes
\fBregexec()\fP to be called with a NULL capture vector. When not testing the
POSIX API, a value of zero is used to cause
\fBpcre2_match_data_create_from_pattern()\fP 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.)
.
.
.SS "Passing the subject as zero-terminated"
.rs
.sp
By default, the subject string is passed to a native API matching function with
its correct length. In order to test the facility for passing a zero-terminated
string, the \fBzero_terminate\fP 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.
.P
When testing \fBpcre2_substitute()\fP, this modifier also has the effect of
passing the replacement string as zero-terminated.
.
.
.SS "Passing a NULL context"
.rs
.sp
Normally, \fBpcre2test\fP passes a context block to \fBpcre2_match()\fP,
\fBpcre2_dfa_match()\fP or \fBpcre2_jit_match()\fP. If the \fBnull_context\fP
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 \fBfind_limits\fP modifier or when testing the
substitution function.
.
.
.SH "THE ALTERNATIVE MATCHING FUNCTION"
.rs
.sp
By default, \fBpcre2test\fP uses the standard PCRE2 matching function,
\fBpcre2_match()\fP to match each subject line. PCRE2 also supports an
alternative matching function, \fBpcre2_dfa_match()\fP, which operates in a
different way, and has some restrictions. The differences between the two
functions are described in the
.\" HREF
\fBpcre2matching\fP
.\"
documentation.
.P
If the \fBdfa\fP modifier is set, the alternative matching function is used.
This function finds all possible matches at a given point in the subject. If,
however, the \fBdfa_shortest\fP modifier is set, processing stops after the
first match is found. This is always the shortest possible match.
.
.
.SH "DEFAULT OUTPUT FROM pcre2test"
.rs
.sp
This section describes the output when the normal matching function,
\fBpcre2_match()\fP, is being used.
.P
When a match succeeds, \fBpcre2test\fP outputs the list of captured substrings,
starting with number 0 for the string that matched the whole pattern.
Otherwise, it outputs "No match" when the return is PCRE2_ERROR_NOMATCH, or
"Partial match:" followed by the partially matching substring when the
return is PCRE2_ERROR_PARTIAL. (Note that this is the
entire substring that was inspected during the partial match; it may include
characters before the actual match start if a lookbehind assertion, \eK, \eb,
or \eB was involved.)
.P
For any other return, \fBpcre2test\fP 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 \fBpcre2test\fP run.
.sp
  $ pcre2test
  PCRE2 version 10.22 2016-07-29
.sp
    re> /^abc(\ed+)/
  data> abc123
   0: abc123
   1: 123
  data> xyz
  No match
.sp
Unset capturing substrings that are not followed by one that is set are not
shown by \fBpcre2test\fP unless the \fBallcaptures\fP 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.
.sp
    re> /(a)|(b)/
  data> a
   0: a
   1: a
  data> b
   0: b
   1: <unset>
   2: b
.sp
If the strings contain any non-printing characters, they are output as \exhh
escapes if the value is less than 256 and UTF mode is not set. Otherwise they
are output as \ex{hh...} escapes. See below for the definition of non-printing
characters. If the \fBaftertext\fP modifier is set, the output for substring
0 is followed by the the rest of the subject string, identified by "0+" like
this:
.sp
    re> /cat/aftertext
  data> cataract
   0: cat
   0+ aract
.sp
If global matching is requested, the results of successive matching attempts
are output in sequence, like this:
.sp
    re> /\eBi(\ew\ew)/g
  data> Mississippi
   0: iss
   1: ss
   0: iss
   1: ss
   0: ipp
   1: pp
.sp
"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 \fBoffset\fP
modifier is past the end of the subject string):
.sp
    re> /xyz/
  data> xyz\e=offset=4
  Error -24 (bad offset value)
.P
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 \en escape (or \er, \er\en, etc.,
depending on the newline sequence setting).
.
.
.
.SH "OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION"
.rs
.sp
When the alternative matching function, \fBpcre2_dfa_match()\fP, 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:
.sp
    re> /(tang|tangerine|tan)/
  data> yellow tangerine\e=dfa
   0: tangerine
   1: tang
   2: tan
.sp
Using the normal matching function on this data finds only "tang". The
longest matching string is always given first (and numbered zero). After a
PCRE2_ERROR_PARTIAL return, the output is "Partial match:", followed by the
partially matching substring. Note that this is the entire substring that was
inspected during the partial match; it may include characters before the actual
match start if a lookbehind assertion, \eb, or \eB was involved. (\eK is not
supported for DFA matching.)
.P
If global matching is requested, the search for further matches resumes
at the end of the longest match. For example:
.sp
    re> /(tang|tangerine|tan)/g
  data> yellow tangerine and tangy sultana\e=dfa
   0: tangerine
   1: tang
   2: tan
   0: tang
   1: tan
   0: tan
.sp
The alternative matching function does not support substring capture, so the
modifiers that are concerned with captured substrings are not relevant.
.
.
.SH "RESTARTING AFTER A PARTIAL MATCH"
.rs
.sp
When the alternative matching function has given the PCRE2_ERROR_PARTIAL
return, indicating that the subject partially matched the pattern, you can
restart the match with additional subject data by means of the
\fBdfa_restart\fP modifier. For example:
.sp
    re> /^\ed?\ed(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\ed\ed$/
  data> 23ja\e=P,dfa
  Partial match: 23ja
  data> n05\e=dfa,dfa_restart
   0: n05
.sp
For further information about partial matching, see the
.\" HREF
\fBpcre2partial\fP
.\"
documentation.
.
.
.SH CALLOUTS
.rs
.sp
If the pattern contains any callout requests, \fBpcre2test\fP's callout
function is called during matching unless \fBcallout_none\fP is specified.
This works with both matching functions.
.P
The callout function in \fBpcre2test\fP returns zero (carry on matching) by
default, but you can use a \fBcallout_fail\fP modifier in a subject line (as
described above) to change this and other parameters of the callout.
.P
Inserting callouts can be helpful when using \fBpcre2test\fP to check
complicated regular expressions. For further information about callouts, see
the
.\" HREF
\fBpcre2callout\fP
.\"
documentation.
.P
The output for callouts with numerical arguments and those with string
arguments is slightly different.
.
.
.SS "Callouts with numerical arguments"
.rs
.sp
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:
.sp
  --->pqrabcdef
    0    ^  ^     \ed
.sp
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 \ed. Just
one circumflex is output if the start and current positions are the same, or if
the current position precedes the start position, which can happen if the
callout is in a lookbehind assertion.
.P
Callouts numbered 255 are assumed to be automatic callouts, inserted as a
result of the \fBauto_callout\fP pattern modifier. In this case, instead of
showing the callout number, the offset in the pattern, preceded by a plus, is
output. For example:
.sp
    re> /\ed?[A-E]\e*/auto_callout
  data> E*
  --->E*
   +0 ^      \ed?
   +3 ^      [A-E]
   +8 ^^     \e*
  +10 ^ ^
   0: E*
.sp
If a pattern contains (*MARK) items, an additional line is output whenever
a change of latest mark is passed to the callout function. For example:
.sp
    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
.sp
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.
.
.
.SS "Callouts with string arguments"
.rs
.sp
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:
.sp
    re> /^ab(?C'first')cd(?C"second")ef/
  data> abcdefg
  Callout (7): 'first'
  --->abcdefg
      ^ ^         c
  Callout (20): "second"
  --->abcdefg
      ^   ^       e
   0: abcdef
.sp
.
.
.
.SH "NON-PRINTING CHARACTERS"
.rs
.sp
When \fBpcre2test\fP 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.
.P
When \fBpcre2test\fP 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 \fBlocale\fP modifier). In this case, the
\fBisprint()\fP function is used to distinguish printing and non-printing
characters.
.
.
.
.\" HTML <a name="saverestore"></a>
.SH "SAVING AND RESTORING COMPILED PATTERNS"
.rs
.sp
It is possible to save compiled patterns on disc or elsewhere, and reload them
later, subject to a number of restrictions. JIT data cannot be saved. The host
on which the patterns are reloaded must be running the same version of PCRE2,
with the same code unit width, and must also have the same endianness, pointer
width and PCRE2_SIZE type. Before compiled patterns can be saved they must be
serialized, that is, converted to a stream of bytes. A single byte stream may
contain any number of compiled patterns, but they must all use the same
character tables. A single copy of the tables is included in the byte stream
(its size is 1088 bytes).
.P
The functions whose names begin with \fBpcre2_serialize_\fP are used
for serializing and de-serializing. They are described in the
.\" HREF
\fBpcre2serialize\fP
.\"
documentation. In this section we describe the features of \fBpcre2test\fP that
can be used to test these functions.
.P
When a pattern with \fBpush\fP modifier is successfully compiled, it is pushed
onto a stack of compiled patterns, and \fBpcre2test\fP expects the next line to
contain a new pattern (or command) instead of a subject line. By contrast,
the \fBpushcopy\fP modifier causes a copy of the compiled pattern to be
stacked, leaving the original available for immediate matching. By using
\fBpush\fP and/or \fBpushcopy\fP, a number of patterns can be compiled and
retained. These modifiers are incompatible with \fBposix\fP, and control
modifiers that act at match time are ignored (with a message) for the stacked
patterns. The \fBjitverify\fP modifier applies only at compile time.
.P
The command
.sp
  #save <filename>
.sp
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
.sp
  #load <filename>
.sp
reads the data in the file, and then arranges for it to be de-serialized, with
the resulting compiled patterns added to the pattern stack. The pattern on the
top of the stack can be retrieved by the #pop command, which must be followed
by lines of subjects that are to be matched with the pattern, terminated as
usual by an empty line or end of file. This command may be followed by a
modifier list containing only
.\" HTML <a href="#controlmodifiers">
.\" </a>
control modifiers
.\"
that act after a pattern has been compiled. In particular, \fBhex\fP,
\fBposix\fP, \fBposix_nosub\fP, \fBpush\fP, and \fBpushcopy\fP are not allowed,
nor are any
.\" HTML <a href="#optionmodifiers">
.\" </a>
option-setting modifiers.
.\"
The JIT modifiers are, however permitted. Here is an example that saves and
reloads two patterns.
.sp
  /abc/push
  /xyz/push
  #save tempfile
  #load tempfile
  #pop info
  xyz
.sp
  #pop jit,bincode
  abc
.sp
If \fBjitverify\fP is used with #pop, it does not automatically imply
\fBjit\fP, which is different behaviour from when it is used on a pattern.
.P
The #popcopy command is analagous to the \fBpushcopy\fP modifier in that it
makes current a copy of the topmost stack pattern, leaving the original still
on the stack.
.
.
.
.SH "SEE ALSO"
.rs
.sp
\fBpcre2\fP(3), \fBpcre2api\fP(3), \fBpcre2callout\fP(3),
\fBpcre2jit\fP, \fBpcre2matching\fP(3), \fBpcre2partial\fP(d),
\fBpcre2pattern\fP(3), \fBpcre2serialize\fP(3).
.
.
.SH AUTHOR
.rs
.sp
.nf
Philip Hazel
University Computing Service
Cambridge, England.
.fi
.
.
.SH REVISION
.rs
.sp
.nf
Last updated: 16 June 2017
Copyright (c) 1997-2017 University of Cambridge.
.fi