pcre2/doc/pcre2test.1

.TH PCRE2TEST 1 "12 August 2014" "PCRE 10.00"
.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. The output shows the result of each match
attempt. Modifiers on the command line, 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- 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.
.
.
.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 (see
below). In Unix-like environments, \fBfgets()\fP treats any bytes other than
newline as data characters. However, in some Windows environments character 26
(hex 1A) causes an immediate end of file, and no further data is read. For
maximum portability, therefore, it is safest to avoid non-printing characters
in \fBpcre2test\fP input files.
.
.
.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-b\fP
Behave as if each pattern has the \fB/fullbincode\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, or ANY
               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
  ebcdic     compiled for an EBCDIC environment
  jit        just-in-time support is available
  pcre16     the 16-bit library was built
  pcre32     the 32-bit library was built
  pcre8      the 8-bit library was built
  utf        UTF and Unicode property 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-help\fP
Output a brief summary these options and then exit.
.TP 10
\fB-i\fP
Behave as if each pattern has the \fB/info\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-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.
.TP10
\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. 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 it is given only one filename argument, it reads from
that file and writes to stdout. Otherwise, it reads from stdin and writes to
stdout, and prompts for each line of input, using "re>" to prompt for regular
expression patterns, and "data>" to prompt for subject lines.
.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 a hash (#) character may appear. This
file format, with some restrictions, can also be processed by the
\fBperltest.pl\fP script that is distributed with PCRE2 as a means of checking
that the behaviour of PCRE2 and Perl is the same.
.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 is a replication
feature that makes it possible to generate long 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 a hash (#) character 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 UTF and Unicode property features. This
is a trigger guard that is used in test files to ensure that UTF/Unicode tests
are not accidentally added to files that are used when UTF support is not
included in the library. This effect 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
  #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.pl\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.pl\fP. The \fP#perltest\fB
command helps detect tests that are accidentally put in the wrong file.
.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 and optional white space. Some modifiers may be given
for both patterns and subject lines, whereas others are valid for one or the
other only. 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".
Modifiers that do not take values may be preceded by a minus sign to turn off a
previous default 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. 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 utf modifier on
the pattern. It is recognized always. There may be any number of hexadecimal
digits inside the braces; invalid values provoke error messages.
.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 marke the end of the subject string and
the start of a modifier list. For example:
.sp
  abc\=notbol,notempty
.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.
.
.
.SH "PATTERN MODIFIERS"
.rs
.sp
There are three types of modifier that can appear in pattern lines, two of
which may also be used in a \fB#pattern\fP command. A pattern's modifier list
can add to or override default modifiers that were set by a previous
\fB#pattern\fP command.
.
.SS "Setting compilation options"
.rs
.sp
The following modifiers set options for \fBpcre2_compile()\fP. The most common
ones have single-letter abbreviations. See
.\" HREF
\fBpcreapi\fP
.\"
for a description of their effects.
.sp
      allow_empty_class         set PCRE2_ALLOW_EMPTY_CLASS
      alt_bsux                  set PCRE2_ALT_BSUX
      anchored                  set PCRE2_ANCHORED
      auto_callout              set PCRE2_AUTO_CALLOUT
  /i  caseless                  set PCRE2_CASELESS
      dollar_endonly            set PCRE2_DOLLAR_ENDONLY
  /s  dotall                    set PCRE2_DOTALL
      dupnames                  set PCRE2_DUPNAMES
  /x  extended                  set PCRE2_EXTENDED
      firstline                 set PCRE2_FIRSTLINE
      match_unset_backref       set PCRE2_MATCH_UNSET_BACKREF
  /m  multiline                 set PCRE2_MULTILINE
      never_ucp                 set PCRE2_NEVER_UCP
      never_utf                 set PCRE2_NEVER_UTF
      no_auto_capture           set PCRE2_NO_AUTO_CAPTURE
      no_auto_possess           set PCRE2_NO_AUTO_POSSESS
      no_start_optimize         set PCRE2_NO_START_OPTIMIZE
      no_utf_check              set PCRE2_NO_UTF_CHECK
      ucp                       set PCRE2_UCP
      ungreedy                  set PCRE2_UNGREEDY
      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.
.
.SS "Setting compilation controls"
.rs
.sp
The following modifiers affect the compilation process or request information
about the pattern:
.sp
      bsr=[anycrlf|unicode]     specify \eR handling
  /B  bincode                   show binary code without lengths
      debug                     same as info,fullbincode
      fullbincode               show binary code with lengths
  /I  info                      show info about compiled pattern
      hex                       pattern is coded in hexadecimal
      jit[=<number>]            use JIT
      locale=<name>             use this locale
      memory                    show memory used
      newline=<type>            set newline type
      parens_nest_limit=<n>     set maximum parentheses depth
      perlcompat                lock out non-Perl modifiers
      posix                     use the POSIX API
      stackguard=<number>       test the stackguard feature
      tables=[0|1|2]            select internal tables
      use_length                use the pattern's length
.sp
The effects of these modifiers are described in the following sections.
FIXME: Give more examples.
.
.
.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 (by default) in subject lines. The type must
be one of CR, LF, CRLF, ANYCRLF, or ANY.
.P
Both the \eR and newline settings can be changed at match time, but if this is
done, JIT matching is disabled.
.
.
.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 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.
.
.
.SS "Specifying a pattern in hex"
.rs
.sp
The \fBhex\fP modifier specifies that the characters of the pattern are to be
interpreted as pairs of hexadecimal digits. White space is permitted between
pairs. For example:
.sp
  /ab 32 59/hex
.sp
This feature is provided as a way of creating patterns that contain binary zero
characters. When \fBhex\fP is set, it implies \fBuse_length\fP.
.
.
.SS "Using the pattern's length"
.rs
.sp
By default, \fBpcre2test\fP passes patterns as zero-terminated strings to
\fBpcre2_compile()\fP, giving the length as -1. If \fBuse_length\fP is set, the
length of the pattern is passed. This is implied if \fBhex\fP is set.
.
.
.SS "JIT compilation"
.rs
.sp
The \fB/jit\fP modifier may optionally be followed by a number in the range 0
to 7:
.sp
  0  disable JIT
  1  normal match only
  2  soft partial match only
  3  normal match and soft partial match
  4  hard partial match only
  6  soft and hard partial match
  7  all three modes
.sp
If no number is given, 7 is assumed. If JIT compilation is successful, the
compiled JIT code will automatically be used when \fBpcre2_match()\fP 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 \fBjitverify\fP modifier is specified, the text "(JIT)" is added to the
first output line after a match or non match when JIT-compiled code was
actually used. This modifier can also be set on a subject line.
.
.
.SS "Setting a locale"
.rs
.sp
The \fB/locale\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 \fB/locale\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 \fB/memory\fP modifier causes the size in bytes of the memory block 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.
.
.
.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.
.
.
.SS "Using the POSIX wrapper API"
.rs
.sp
The \fB/posix\fP modifier causes \fBpcre2test\fP to call PCRE2 via the POSIX
wrapper API rather than its native API. This supports only the 8-bit library.
When the POSIX API is being used, the following pattern modifiers set options
for the \fBregcomp()\fP function:
.sp
  caseless           REG_ICASE
  multiline          REG_NEWLINE
  no_auto_capture    REG_NOSUB
  dotall             REG_DOTALL     )
  ungreedy           REG_UNGREEDY   ) These options are not part of
  ucp                REG_UCP        )   the POSIX standard
  utf                REG_UTF8       )
.sp
The \fBaftertext\fP and \fBallaftertext\fP subject modifiers work as described
below. All other modifiers cause an error.
.
.
.SS "Testing the stack guard feature"
.rs
.sp
The \fB/stackguard\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 is
passed 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 \fB/tables\fP modifier must be followed by a single digit. 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 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 do
not affect the compilation process.
.sp
      aftertext                 show text after match
      allaftertext              show text after captures
      allcaptures               show all captures
  /g  global                    global matching
      jitverify                 verify JIT usage
      mark                      show mark values
.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.
.
.
.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
      dfa_restart               set PCRE2_DFA_RESTART
      dfa_shortest              set PCRE2_DFA_SHORTEST
      no_start_optimize         set PCRE2_NO_START_OPTIMIZE
      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 \fB/posix\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.
Any other modifiers cause an error.
.
.
.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
      altglobal                 alternative global matching
      bsr=[anycrlf|unicode]     specify \eR handling
      callout_capture           show captures at callout time
      callout_data=<n>          set a value to pass via callouts
      callout_fail=<n>[:<m>]    control callout failure
      callout_none              do not supply a callout function
      copy=<number or name>     copy captured substring
      dfa                       use \fBpcre2_dfa_match()\fP
      find_limits               find match and recursion limits
      get=<number or name>      extract captured substring
      getall                    extract all captured substrings
  /g  global                    global matching
      jitstack=<n>              set size of JIT stack
      jitverify                 verify JIT usage
      mark                      show mark values
      match_limit=>n>           set a match limit
      memory                    show memory usage
      newline=<type>            set newline type
      offset=<n>                set starting offset
      ovector=<n>               set size of output vector
      recursion_limit=<n>       set a recursion limit
.sp
The effects of these modifiers are described in the following sections.
FIXME: Give more examples.
.
.
.SS "Newline and \eR handling"
.rs
.sp
These modifiers set the newline and \eR processing conventions for the subject
line, overriding any values that were set at compile time (as described above).
JIT matching is disabled if these settings are changed at match time.
.
.
.SS "Showing more text"
.rs
.sp
The \fBaftertext\fP modifier requests that as well as outputting the substring
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.
.
.
.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>".
.
.
.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.
.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 when a callout of that number is
reached. If two numbers are given, 1 is returned when callout <n> is reached
for the <m>th time.
.P
The \fBcallout_data\fP modifier can be given an unsigned or a negative number.
Any value other than zero is used as a return from \fBpcre2test\fP's callout
function.
.
.
.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\=copy=1,copy=3,get=G1
.sp
If the \fB#subject\fP command is used to set default copy and get lists, these
can be unset by specifying a negative number for numbered groups and an empty
name for 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.
.
.
.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 \fB/altglobal\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 substring. 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 is used.
.
.
.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. Providing a stack that is larger than the
default 32K is necessary only for very complicated patterns.
.
.
.SS "Setting match and recursion limits"
.rs
.sp
The \fBmatch_limit\fP and \fBrecursion_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, \fBpcre2test\fP calls
\fBpcre2_match()\fP several times, setting different values in the match
context via \fBpcre2_set_match_limit()\fP and \fBpcre2_set_recursion_limit()\fP
until it finds the minimum values for each parameter that allow
\fBpcre2_match()\fP to complete without error.
.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. The \fImatch_limit_recursion\fP number is
a measure of how much stack (or, if PCRE2 is compiled with NO_RECURSE, how much
heap) memory is needed to complete the match attempt.
.
.
.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 all memory allocation
and freeing calls that occur during a match operation.
.
.
.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 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.
.
.
.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 offset of the start of the failing character and the
reason code are also output. Here is an example of an interactive
\fBpcre2test\fP run.
.sp
  $ pcre2test
  PCRE2 version 9.00 2014-05-10
.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
returned by \fBpcre2_match()\fP, and are not shown by \fBpcre2test\fP. 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 \fB/aftertext\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 \e>4 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, \eK, \eb, or \eB was involved.)
.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. This works with both matching functions. By default,
the called function displays the callout number, the start and current
positions in the 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.
.P
Callouts numbered 255 are assumed to be automatic callouts, inserted as a
result of the \fB/auto_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.
.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.
.
.
.
.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 \fB/locale\fP modifier). In this case, the
\fBisprint()\fP function is used to distinguish printing and non-printing
characters.
.
.
.
.SH "SEE ALSO"
.rs
.sp
\fBpcre2\fP(3), \fBpcre16\fP(3), \fBpcre32\fP(3), \fBpcre2api\fP(3),
\fBpcre2callout\fP(3),
\fBpcre2jit\fP, \fBpcre2matching\fP(3), \fBpcre2partial\fP(d),
\fBpcre2pattern\fP(3), \fBpcre2precompile\fP(3).
.
.
.SH AUTHOR
.rs
.sp
.nf
Philip Hazel
University Computing Service
Cambridge CB2 3QH, England.
.fi
.
.
.SH REVISION
.rs
.sp
.nf
Last updated: 12 August 2014
Copyright (c) 1997-2014 University of Cambridge.
.fi