trunk/doc/pcretest.1

.TH PCRETEST 1
.SH NAME
pcretest - a program for testing Perl-compatible regular expressions.
.SH SYNOPSIS
.B pcretest "[-d] [-i] [-m] [-o osize] [-p] [-t] [source] [destination]"

\fBpcretest\fR was written as a test program for the PCRE regular expression
library itself, 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
\fBpcrepattern\fR
.\"
documentation. For details of PCRE and its options, see the
.\" HREF
\fBpcreapi\fR
.\"
documentation.

.SH OPTIONS
.rs
.sp
.TP 10
\fB-C\fR
Output the version number of the PCRE library, and all available information
about the optional features that are included, and then exit.
.TP 10
\fB-d\fR
Behave as if each regex had the \fB/D\fR modifier (see below); the internal
form is output after compilation.
.TP 10
\fB-i\fR
Behave as if each regex had the \fB/I\fR modifier; information about the
compiled pattern is given after compilation.
.TP 10
\fB-m\fR
Output the size of each compiled pattern after it has been compiled. This is
equivalent to adding /M to each regular expression. For compatibility with
earlier versions of pcretest, \fB-s\fR is a synonym for \fB-m\fR.
.TP 10
\fB-o\fR \fIosize\fR
Set the number of elements in the output vector that is used when calling PCRE
to be \fIosize\fR. The default value is 45, which is enough for 14 capturing
subexpressions. The vector size can be changed for individual matching calls by
including \\O in the data line (see below).
.TP 10
\fB-p\fR
Behave as if each regex has \fB/P\fR modifier; the POSIX wrapper API is used
to call PCRE. None of the other options has any effect when \fB-p\fR is set.
.TP 10
\fB-t\fR
Run each compile, study, and match many times with a timer, and output
resulting time per compile or match (in milliseconds). Do not set \fB-t\fR with
\fB-m\fR, because you will then get the size output 20000 times and the timing
will be distorted.

.SH DESCRIPTION
.rs
.sp
If \fBpcretest\fR 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
expressions, and "data>" to prompt for data lines.

The program handles any number of sets of input on a single input file. Each
set starts with a regular expression, and continues with any number of data
lines to be matched against the pattern.

Each line is matched separately and independently. If you want to do
multiple-line matches, you have to use the \\n escape sequence in a single line
of input to encode the newline characters. The maximum length of data line is
30,000 characters.

An empty line signals the end of the data lines, at which point a new regular
expression is read. The regular expressions are given enclosed in any
non-alphameric delimiters other than backslash, for example

  /(a|bc)x+yz/

White space before the initial delimiter is ignored. 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, for example

  /abc\\/def/

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

  /abc/\\

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

  /abc\\/

is interpreted as the first line of a pattern that starts with "abc/", causing
pcretest to read the next line as a continuation of the regular expression.

.SH PATTERN MODIFIERS
.rs
.sp
The pattern may be followed by \fBi\fR, \fBm\fR, \fBs\fR, or \fBx\fR to set the
PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options,
respectively. For example:

  /caseless/i

These modifier letters have the same effect as they do in Perl. There are
others that set PCRE options that do not correspond to anything in Perl:
\fB/A\fR, \fB/E\fR, \fB/N\fR, \fB/U\fR, and \fB/X\fR set PCRE_ANCHORED,
PCRE_DOLLAR_ENDONLY, PCRE_NO_AUTO_CAPTURE, PCRE_UNGREEDY, and PCRE_EXTRA
respectively.

Searching for all possible matches within each subject string can be requested
by the \fB/g\fR or \fB/G\fR modifier. After finding a match, PCRE is called
again to search the remainder of the subject string. The difference between
\fB/g\fR and \fB/G\fR is that the former uses the \fIstartoffset\fR argument to
\fBpcre_exec()\fR to start searching at a new point within the entire string
(which is in effect 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 \\b or \\B).

If any call to \fBpcre_exec()\fR in a \fB/g\fR or \fB/G\fR sequence matches an
empty string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
flags set in order to search for another, non-empty, match at the same point.
If this second match fails, the start offset is advanced by one, and the normal
match is retried. This imitates the way Perl handles such cases when using the
\fB/g\fR modifier or the \fBsplit()\fR function.

There are a number of other modifiers for controlling the way \fBpcretest\fR
operates.

The \fB/+\fR modifier requests that as well as outputting the substring that
matched the entire pattern, pcretest 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 \fB/L\fR modifier must be followed directly by the name of a locale, for
example,

  /pattern/Lfr

For this reason, it must be the last modifier letter. The given locale is set,
\fBpcre_maketables()\fR is called to build a set of character tables for the
locale, and this is then passed to \fBpcre_compile()\fR when compiling the
regular expression. Without an \fB/L\fR modifier, NULL is passed as the tables
pointer; that is, \fB/L\fR applies only to the expression on which it appears.

The \fB/I\fR modifier requests that \fBpcretest\fR output information about the
compiled expression (whether it is anchored, has a fixed first character, and
so on). It does this by calling \fBpcre_fullinfo()\fR after compiling an
expression, and outputting the information it gets back. If the pattern is
studied, the results of that are also output.

The \fB/D\fR modifier is a PCRE debugging feature, which also assumes \fB/I\fR.
It causes the internal form of compiled regular expressions to be output after
compilation. If the pattern was studied, the information returned is also
output.

The \fB/S\fR modifier causes \fBpcre_study()\fR to be called after the
expression has been compiled, and the results used when the expression is
matched.

The \fB/M\fR modifier causes the size of memory block used to hold the compiled
pattern to be output.

The \fB/P\fR modifier causes \fBpcretest\fR to call PCRE via the POSIX wrapper
API rather than its native API. When this is done, all other modifiers except
\fB/i\fR, \fB/m\fR, and \fB/+\fR are ignored. REG_ICASE is set if \fB/i\fR is
present, and REG_NEWLINE is set if \fB/m\fR is present. The wrapper functions
force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set.

The \fB/8\fR modifier causes \fBpcretest\fR to call PCRE with the PCRE_UTF8
option set. This turns on support for UTF-8 character handling in PCRE,
provided that it was compiled with this support enabled. This modifier also
causes any non-printing characters in output strings to be printed using the
\\x{hh...} notation if they are valid UTF-8 sequences.

If the \fB/?\fR modifier is used with \fB/8\fR, it causes \fBpcretest\fR to
call \fBpcre_compile()\fR with the PCRE_NO_UTF8_CHECK option, to suppress the
checking of the string for UTF-8 validity.

.SH CALLOUTS
.rs
.sp
If the pattern contains any callout requests, \fBpcretest\fR's callout function
will be called. By default, it displays the callout number, and the start and
current positions in the text at the callout time. For example, the output

  --->pqrabcdef
    0    ^  ^

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. The callout function returns zero (carry on matching) by default.

Inserting callouts may be helpful when using \fBpcretest\fR to check
complicated regular expressions. For further information about callouts, see
the
.\" HREF
\fBpcrecallout\fR
.\"
documentation.

For testing the PCRE library, additional control of callout behaviour is
available via escape sequences in the data, as described in the following
section. In particular, it is possible to pass in a number as callout data (the
default is zero). If the callout function receives a non-zero number, it
returns that value instead of zero.

.SH DATA LINES
.rs
.sp
Before each data line is passed to \fBpcre_exec()\fR, leading and trailing
whitespace is removed, and it is then scanned for \\ escapes. Some of these are
pretty esoteric features, intended for checking out some of the more
complicated features of PCRE. If you are just testing "ordinary" regular
expressions, you probably don't need any of these. The following escapes are
recognized:

  \\a         alarm (= BEL)
  \\b         backspace
  \\e         escape
  \\f         formfeed
  \\n         newline
  \\r         carriage return
  \\t         tab
  \\v         vertical tab
  \\nnn       octal character (up to 3 octal digits)
  \\xhh       hexadecimal character (up to 2 hex digits)
  \\x{hh...}  hexadecimal character, any number of digits
               in UTF-8 mode
  \\A         pass the PCRE_ANCHORED option to \fBpcre_exec()\fR
  \\B         pass the PCRE_NOTBOL option to \fBpcre_exec()\fR
  \\Cdd       call pcre_copy_substring() for substring dd
               after a successful match (any decimal number
               less than 32)
  \\Cname     call pcre_copy_named_substring() for substring
               "name" after a successful match (name termin-
               ated by next non alphanumeric character)
  \\C+        show the current captured substrings at callout
               time
  \\C-        do not supply a callout function
  \\C!n       return 1 instead of 0 when callout number n is
               reached
  \\C!n!m     return 1 instead of 0 when callout number n is
               reached for the nth time
  \\C*n       pass the number n (may be negative) as callout
               data
  \\Gdd       call pcre_get_substring() for substring dd
               after a successful match (any decimal number
               less than 32)
  \\Gname     call pcre_get_named_substring() for substring
               "name" after a successful match (name termin-
               ated by next non-alphanumeric character)
  \\L         call pcre_get_substringlist() after a
               successful match
  \\M         discover the minimum MATCH_LIMIT setting
  \\N         pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fR
  \\Odd       set the size of the output vector passed to
               \fBpcre_exec()\fR to dd (any number of decimal
               digits)
  \\Z         pass the PCRE_NOTEOL option to \fBpcre_exec()\fR
  \\?         pass the PCRE_NO_UTF8_CHECK option to
               \fBpcre_exec()\fR

If \\M is present, \fBpcretest\fR calls \fBpcre_exec()\fR several times, with
different values in the \fImatch_limit\fR field of the \fBpcre_extra\fR data
structure, until it finds the minimum number that is needed for
\fBpcre_exec()\fR to complete. This number is a measure of the amount of
recursion and backtracking that takes place, and checking it out 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.

When \\O is used, it may be higher or lower than the size set by the \fB-O\fR
option (or defaulted to 45); \\O applies only to the call of \fBpcre_exec()\fR
for the line in which it appears.

A backslash followed by anything else just escapes the anything else. If the
very last character is a backslash, it is ignored. This gives a way of passing
an empty line as data, since a real empty line terminates the data input.

If \fB/P\fR was present on the regex, causing the POSIX wrapper API to be used,
only \fB\B\fR, and \fB\Z\fR have any effect, causing REG_NOTBOL and REG_NOTEOL
to be passed to \fBregexec()\fR respectively.

The use of \\x{hh...} to represent UTF-8 characters is not dependent on the use
of the \fB/8\fR modifier on the pattern. It is recognized always. There may be
any number of hexadecimal digits inside the braces. The result is from one to
six bytes, encoded according to the UTF-8 rules.

.SH OUTPUT FROM PCRETEST
.rs
.sp
When a match succeeds, pcretest outputs the list of captured substrings that
\fBpcre_exec()\fR returns, starting with number 0 for the string that matched
the whole pattern. Here is an example of an interactive pcretest run.

  $ pcretest
  PCRE version 4.00 08-Jan-2003

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

If the strings contain any non-printing characters, they are output as \\0x
escapes, or as \\x{...} escapes if the \fB/8\fR modifier was present on the
pattern. If the pattern has the \fB/+\fR modifier, then the output for
substring 0 is followed by the the rest of the subject string, identified by
"0+" like this:

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

If the pattern has the \fB/g\fR or \fB/G\fR modifier, the results of successive
matching attempts are output in sequence, like this:

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

"No match" is output only if the first match attempt fails.

If any of the sequences \fB\\C\fR, \fB\\G\fR, or \fB\\L\fR are present in a
data line that 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 string for \fB\\C\fR and \fB\\G\fR.

Note that while patterns can be continued over several lines (a plain ">"
prompt is used for continuations), data lines may not. However newlines can be
included in data by means of the \\n escape.

.SH AUTHOR
.rs
.sp
Philip Hazel <ph10@cam.ac.uk>
.br
University Computing Service,
.br
Cambridge CB2 3QG, England.

.in 0
Last updated: 20 August 2003
.br
Copyright (c) 1997-2003 University of Cambridge.
1	nigel	53	.TH PCRETEST 1
2			.SH NAME
3			pcretest - a program for testing Perl-compatible regular expressions.
4			.SH SYNOPSIS
5			.B pcretest "[-d] [-i] [-m] [-o osize] [-p] [-t] [source] [destination]"
6
7			\fBpcretest\fR was written as a test program for the PCRE regular expression
8			library itself, but it can also be used for experimenting with regular
9	nigel	63	expressions. This document describes the features of the test program; for
10			details of the regular expressions themselves, see the
11			.\" HREF
12			\fBpcrepattern\fR
13			.\"
14			documentation. For details of PCRE and its options, see the
15			.\" HREF
16			\fBpcreapi\fR
17			.\"
18			documentation.
19	nigel	53
20			.SH OPTIONS
21	nigel	63	.rs
22			.sp
23	nigel	53	.TP 10
24	nigel	63	\fB-C\fR
25			Output the version number of the PCRE library, and all available information
26			about the optional features that are included, and then exit.
27			.TP 10
28	nigel	53	\fB-d\fR
29			Behave as if each regex had the \fB/D\fR modifier (see below); the internal
30			form is output after compilation.
31			.TP 10
32			\fB-i\fR
33			Behave as if each regex had the \fB/I\fR modifier; information about the
34			compiled pattern is given after compilation.
35			.TP 10
36			\fB-m\fR
37			Output the size of each compiled pattern after it has been compiled. This is
38			equivalent to adding /M to each regular expression. For compatibility with
39			earlier versions of pcretest, \fB-s\fR is a synonym for \fB-m\fR.
40			.TP 10
41			\fB-o\fR \fIosize\fR
42			Set the number of elements in the output vector that is used when calling PCRE
43			to be \fIosize\fR. The default value is 45, which is enough for 14 capturing
44			subexpressions. The vector size can be changed for individual matching calls by
45			including \\O in the data line (see below).
46			.TP 10
47			\fB-p\fR
48			Behave as if each regex has \fB/P\fR modifier; the POSIX wrapper API is used
49			to call PCRE. None of the other options has any effect when \fB-p\fR is set.
50			.TP 10
51			\fB-t\fR
52	nigel	63	Run each compile, study, and match many times with a timer, and output
53	nigel	53	resulting time per compile or match (in milliseconds). Do not set \fB-t\fR with
54			\fB-m\fR, because you will then get the size output 20000 times and the timing
55			will be distorted.
56
57			.SH DESCRIPTION
58	nigel	63	.rs
59			.sp
60	nigel	53	If \fBpcretest\fR is given two filename arguments, it reads from the first and
61			writes to the second. If it is given only one filename argument, it reads from
62			that file and writes to stdout. Otherwise, it reads from stdin and writes to
63			stdout, and prompts for each line of input, using "re>" to prompt for regular
64			expressions, and "data>" to prompt for data lines.
65
66			The program handles any number of sets of input on a single input file. Each
67			set starts with a regular expression, and continues with any number of data
68	nigel	63	lines to be matched against the pattern.
69	nigel	53
70	nigel	63	Each line is matched separately and independently. If you want to do
71			multiple-line matches, you have to use the \\n escape sequence in a single line
72			of input to encode the newline characters. The maximum length of data line is
73			30,000 characters.
74
75			An empty line signals the end of the data lines, at which point a new regular
76			expression is read. The regular expressions are given enclosed in any
77			non-alphameric delimiters other than backslash, for example
78
79	nigel	53	/(a\|bc)x+yz/
80
81			White space before the initial delimiter is ignored. A regular expression may
82			be continued over several input lines, in which case the newline characters are
83			included within it. It is possible to include the delimiter within the pattern
84			by escaping it, for example
85
86			/abc\\/def/
87
88			If you do so, the escape and the delimiter form part of the pattern, but since
89			delimiters are always non-alphameric, this does not affect its interpretation.
90			If the terminating delimiter is immediately followed by a backslash, for
91			example,
92
93			/abc/\\
94
95			then a backslash is added to the end of the pattern. This is done to provide a
96			way of testing the error condition that arises if a pattern finishes with a
97			backslash, because
98
99			/abc\\/
100
101			is interpreted as the first line of a pattern that starts with "abc/", causing
102			pcretest to read the next line as a continuation of the regular expression.
103
104			.SH PATTERN MODIFIERS
105	nigel	63	.rs
106			.sp
107	nigel	53	The pattern may be followed by \fBi\fR, \fBm\fR, \fBs\fR, or \fBx\fR to set the
108			PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options,
109			respectively. For example:
110
111			/caseless/i
112
113			These modifier letters have the same effect as they do in Perl. There are
114	nigel	71	others that set PCRE options that do not correspond to anything in Perl:
115			\fB/A\fR, \fB/E\fR, \fB/N\fR, \fB/U\fR, and \fB/X\fR set PCRE_ANCHORED,
116			PCRE_DOLLAR_ENDONLY, PCRE_NO_AUTO_CAPTURE, PCRE_UNGREEDY, and PCRE_EXTRA
117			respectively.
118	nigel	53
119			Searching for all possible matches within each subject string can be requested
120			by the \fB/g\fR or \fB/G\fR modifier. After finding a match, PCRE is called
121			again to search the remainder of the subject string. The difference between
122			\fB/g\fR and \fB/G\fR is that the former uses the \fIstartoffset\fR argument to
123			\fBpcre_exec()\fR to start searching at a new point within the entire string
124			(which is in effect what Perl does), whereas the latter passes over a shortened
125			substring. This makes a difference to the matching process if the pattern
126			begins with a lookbehind assertion (including \\b or \\B).
127
128			If any call to \fBpcre_exec()\fR in a \fB/g\fR or \fB/G\fR sequence matches an
129			empty string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
130			flags set in order to search for another, non-empty, match at the same point.
131			If this second match fails, the start offset is advanced by one, and the normal
132			match is retried. This imitates the way Perl handles such cases when using the
133			\fB/g\fR modifier or the \fBsplit()\fR function.
134
135			There are a number of other modifiers for controlling the way \fBpcretest\fR
136			operates.
137
138			The \fB/+\fR modifier requests that as well as outputting the substring that
139			matched the entire pattern, pcretest should in addition output the remainder of
140			the subject string. This is useful for tests where the subject contains
141			multiple copies of the same substring.
142
143			The \fB/L\fR modifier must be followed directly by the name of a locale, for
144			example,
145
146			/pattern/Lfr
147
148			For this reason, it must be the last modifier letter. The given locale is set,
149			\fBpcre_maketables()\fR is called to build a set of character tables for the
150			locale, and this is then passed to \fBpcre_compile()\fR when compiling the
151			regular expression. Without an \fB/L\fR modifier, NULL is passed as the tables
152			pointer; that is, \fB/L\fR applies only to the expression on which it appears.
153
154			The \fB/I\fR modifier requests that \fBpcretest\fR output information about the
155			compiled expression (whether it is anchored, has a fixed first character, and
156			so on). It does this by calling \fBpcre_fullinfo()\fR after compiling an
157			expression, and outputting the information it gets back. If the pattern is
158			studied, the results of that are also output.
159
160			The \fB/D\fR modifier is a PCRE debugging feature, which also assumes \fB/I\fR.
161			It causes the internal form of compiled regular expressions to be output after
162	nigel	63	compilation. If the pattern was studied, the information returned is also
163			output.
164	nigel	53
165			The \fB/S\fR modifier causes \fBpcre_study()\fR to be called after the
166			expression has been compiled, and the results used when the expression is
167			matched.
168
169			The \fB/M\fR modifier causes the size of memory block used to hold the compiled
170			pattern to be output.
171
172			The \fB/P\fR modifier causes \fBpcretest\fR to call PCRE via the POSIX wrapper
173			API rather than its native API. When this is done, all other modifiers except
174			\fB/i\fR, \fB/m\fR, and \fB/+\fR are ignored. REG_ICASE is set if \fB/i\fR is
175			present, and REG_NEWLINE is set if \fB/m\fR is present. The wrapper functions
176			force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set.
177
178			The \fB/8\fR modifier causes \fBpcretest\fR to call PCRE with the PCRE_UTF8
179	nigel	63	option set. This turns on support for UTF-8 character handling in PCRE,
180			provided that it was compiled with this support enabled. This modifier also
181			causes any non-printing characters in output strings to be printed using the
182			\\x{hh...} notation if they are valid UTF-8 sequences.
183	nigel	53
184	nigel	71	If the \fB/?\fR modifier is used with \fB/8\fR, it causes \fBpcretest\fR to
185			call \fBpcre_compile()\fR with the PCRE_NO_UTF8_CHECK option, to suppress the
186			checking of the string for UTF-8 validity.
187
188	nigel	63	.SH CALLOUTS
189			.rs
190			.sp
191			If the pattern contains any callout requests, \fBpcretest\fR's callout function
192			will be called. By default, it displays the callout number, and the start and
193			current positions in the text at the callout time. For example, the output
194	nigel	53
195	nigel	63	--->pqrabcdef
196			0 ^ ^
197
198			indicates that callout number 0 occurred for a match attempt starting at the
199			fourth character of the subject string, when the pointer was at the seventh
200			character. The callout function returns zero (carry on matching) by default.
201
202			Inserting callouts may be helpful when using \fBpcretest\fR to check
203			complicated regular expressions. For further information about callouts, see
204			the
205			.\" HREF
206			\fBpcrecallout\fR
207			.\"
208			documentation.
209
210			For testing the PCRE library, additional control of callout behaviour is
211			available via escape sequences in the data, as described in the following
212			section. In particular, it is possible to pass in a number as callout data (the
213			default is zero). If the callout function receives a non-zero number, it
214			returns that value instead of zero.
215
216	nigel	53	.SH DATA LINES
217	nigel	63	.rs
218			.sp
219	nigel	53	Before each data line is passed to \fBpcre_exec()\fR, leading and trailing
220	nigel	63	whitespace is removed, and it is then scanned for \\ escapes. Some of these are
221			pretty esoteric features, intended for checking out some of the more
222			complicated features of PCRE. If you are just testing "ordinary" regular
223			expressions, you probably don't need any of these. The following escapes are
224	nigel	53	recognized:
225
226			\\a alarm (= BEL)
227			\\b backspace
228			\\e escape
229			\\f formfeed
230			\\n newline
231			\\r carriage return
232			\\t tab
233			\\v vertical tab
234			\\nnn octal character (up to 3 octal digits)
235			\\xhh hexadecimal character (up to 2 hex digits)
236	nigel	63	\\x{hh...} hexadecimal character, any number of digits
237			in UTF-8 mode
238	nigel	53	\\A pass the PCRE_ANCHORED option to \fBpcre_exec()\fR
239			\\B pass the PCRE_NOTBOL option to \fBpcre_exec()\fR
240			\\Cdd call pcre_copy_substring() for substring dd
241	nigel	63	after a successful match (any decimal number
242			less than 32)
243			\\Cname call pcre_copy_named_substring() for substring
244			"name" after a successful match (name termin-
245			ated by next non alphanumeric character)
246			\\C+ show the current captured substrings at callout
247			time
248			\\C- do not supply a callout function
249			\\C!n return 1 instead of 0 when callout number n is
250			reached
251			\\C!n!m return 1 instead of 0 when callout number n is
252			reached for the nth time
253			\\C*n pass the number n (may be negative) as callout
254			data
255	nigel	53	\\Gdd call pcre_get_substring() for substring dd
256	nigel	63	after a successful match (any decimal number
257			less than 32)
258			\\Gname call pcre_get_named_substring() for substring
259			"name" after a successful match (name termin-
260			ated by next non-alphanumeric character)
261	nigel	53	\\L call pcre_get_substringlist() after a
262	nigel	63	successful match
263			\\M discover the minimum MATCH_LIMIT setting
264	nigel	53	\\N pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fR
265			\\Odd set the size of the output vector passed to
266	nigel	63	\fBpcre_exec()\fR to dd (any number of decimal
267			digits)
268	nigel	53	\\Z pass the PCRE_NOTEOL option to \fBpcre_exec()\fR
269	nigel	71	\\? pass the PCRE_NO_UTF8_CHECK option to
270			\fBpcre_exec()\fR
271	nigel	53
272	nigel	63	If \\M is present, \fBpcretest\fR calls \fBpcre_exec()\fR several times, with
273			different values in the \fImatch_limit\fR field of the \fBpcre_extra\fR data
274			structure, until it finds the minimum number that is needed for
275			\fBpcre_exec()\fR to complete. This number is a measure of the amount of
276			recursion and backtracking that takes place, and checking it out can be
277			instructive. For most simple matches, the number is quite small, but for
278			patterns with very large numbers of matching possibilities, it can become large
279			very quickly with increasing length of subject string.
280
281	nigel	53	When \\O is used, it may be higher or lower than the size set by the \fB-O\fR
282			option (or defaulted to 45); \\O applies only to the call of \fBpcre_exec()\fR
283			for the line in which it appears.
284
285			A backslash followed by anything else just escapes the anything else. If the
286			very last character is a backslash, it is ignored. This gives a way of passing
287			an empty line as data, since a real empty line terminates the data input.
288
289			If \fB/P\fR was present on the regex, causing the POSIX wrapper API to be used,
290			only \fB\B\fR, and \fB\Z\fR have any effect, causing REG_NOTBOL and REG_NOTEOL
291			to be passed to \fBregexec()\fR respectively.
292
293			The use of \\x{hh...} to represent UTF-8 characters is not dependent on the use
294			of the \fB/8\fR modifier on the pattern. It is recognized always. There may be
295			any number of hexadecimal digits inside the braces. The result is from one to
296			six bytes, encoded according to the UTF-8 rules.
297
298			.SH OUTPUT FROM PCRETEST
299	nigel	63	.rs
300			.sp
301	nigel	53	When a match succeeds, pcretest outputs the list of captured substrings that
302			\fBpcre_exec()\fR returns, starting with number 0 for the string that matched
303			the whole pattern. Here is an example of an interactive pcretest run.
304
305			$ pcretest
306	nigel	63	PCRE version 4.00 08-Jan-2003
307	nigel	53
308			re> /^abc(\\d+)/
309			data> abc123
310			0: abc123
311			1: 123
312			data> xyz
313			No match
314
315			If the strings contain any non-printing characters, they are output as \\0x
316			escapes, or as \\x{...} escapes if the \fB/8\fR modifier was present on the
317			pattern. If the pattern has the \fB/+\fR modifier, then the output for
318			substring 0 is followed by the the rest of the subject string, identified by
319			"0+" like this:
320
321			re> /cat/+
322			data> cataract
323			0: cat
324			0+ aract
325
326			If the pattern has the \fB/g\fR or \fB/G\fR modifier, the results of successive
327			matching attempts are output in sequence, like this:
328
329			re> /\\Bi(\\w\\w)/g
330			data> Mississippi
331			0: iss
332			1: ss
333			0: iss
334			1: ss
335			0: ipp
336			1: pp
337
338			"No match" is output only if the first match attempt fails.
339
340			If any of the sequences \fB\\C\fR, \fB\\G\fR, or \fB\\L\fR are present in a
341			data line that is successfully matched, the substrings extracted by the
342			convenience functions are output with C, G, or L after the string number
343			instead of a colon. This is in addition to the normal full list. The string
344			length (that is, the return from the extraction function) is given in
345			parentheses after each string for \fB\\C\fR and \fB\\G\fR.
346
347			Note that while patterns can be continued over several lines (a plain ">"
348			prompt is used for continuations), data lines may not. However newlines can be
349			included in data by means of the \\n escape.
350
351			.SH AUTHOR
352	nigel	63	.rs
353			.sp
354	nigel	53	Philip Hazel <ph10@cam.ac.uk>
355			.br
356			University Computing Service,
357			.br
358			Cambridge CB2 3QG, England.
359
360	nigel	63	.in 0
361	nigel	71	Last updated: 20 August 2003
362	nigel	53	.br
363	nigel	63	Copyright (c) 1997-2003 University of Cambridge.