pcre-4.0/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 which set PCRE options that do not correspond to anything in Perl:
\fB/A\fR, \fB/E\fR, and \fB/X\fR set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, 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.

.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

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: 03 February 2003
.br
Copyright (c) 1997-2003 University of Cambridge.
1	.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	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
20	.SH OPTIONS
21	.rs
22	.sp
23	.TP 10
24	\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	\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	Run each compile, study, and match many times with a timer, and output
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	.rs
59	.sp
60	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	lines to be matched against the pattern.
69
70	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	/(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	.rs
106	.sp
107	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	others which set PCRE options that do not correspond to anything in Perl:
115	\fB/A\fR, \fB/E\fR, and \fB/X\fR set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and
116	PCRE_EXTRA respectively.
117
118	Searching for all possible matches within each subject string can be requested
119	by the \fB/g\fR or \fB/G\fR modifier. After finding a match, PCRE is called
120	again to search the remainder of the subject string. The difference between
121	\fB/g\fR and \fB/G\fR is that the former uses the \fIstartoffset\fR argument to
122	\fBpcre_exec()\fR to start searching at a new point within the entire string
123	(which is in effect what Perl does), whereas the latter passes over a shortened
124	substring. This makes a difference to the matching process if the pattern
125	begins with a lookbehind assertion (including \\b or \\B).
126
127	If any call to \fBpcre_exec()\fR in a \fB/g\fR or \fB/G\fR sequence matches an
128	empty string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
129	flags set in order to search for another, non-empty, match at the same point.
130	If this second match fails, the start offset is advanced by one, and the normal
131	match is retried. This imitates the way Perl handles such cases when using the
132	\fB/g\fR modifier or the \fBsplit()\fR function.
133
134	There are a number of other modifiers for controlling the way \fBpcretest\fR
135	operates.
136
137	The \fB/+\fR modifier requests that as well as outputting the substring that
138	matched the entire pattern, pcretest should in addition output the remainder of
139	the subject string. This is useful for tests where the subject contains
140	multiple copies of the same substring.
141
142	The \fB/L\fR modifier must be followed directly by the name of a locale, for
143	example,
144
145	/pattern/Lfr
146
147	For this reason, it must be the last modifier letter. The given locale is set,
148	\fBpcre_maketables()\fR is called to build a set of character tables for the
149	locale, and this is then passed to \fBpcre_compile()\fR when compiling the
150	regular expression. Without an \fB/L\fR modifier, NULL is passed as the tables
151	pointer; that is, \fB/L\fR applies only to the expression on which it appears.
152
153	The \fB/I\fR modifier requests that \fBpcretest\fR output information about the
154	compiled expression (whether it is anchored, has a fixed first character, and
155	so on). It does this by calling \fBpcre_fullinfo()\fR after compiling an
156	expression, and outputting the information it gets back. If the pattern is
157	studied, the results of that are also output.
158
159	The \fB/D\fR modifier is a PCRE debugging feature, which also assumes \fB/I\fR.
160	It causes the internal form of compiled regular expressions to be output after
161	compilation. If the pattern was studied, the information returned is also
162	output.
163
164	The \fB/S\fR modifier causes \fBpcre_study()\fR to be called after the
165	expression has been compiled, and the results used when the expression is
166	matched.
167
168	The \fB/M\fR modifier causes the size of memory block used to hold the compiled
169	pattern to be output.
170
171	The \fB/P\fR modifier causes \fBpcretest\fR to call PCRE via the POSIX wrapper
172	API rather than its native API. When this is done, all other modifiers except
173	\fB/i\fR, \fB/m\fR, and \fB/+\fR are ignored. REG_ICASE is set if \fB/i\fR is
174	present, and REG_NEWLINE is set if \fB/m\fR is present. The wrapper functions
175	force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set.
176
177	The \fB/8\fR modifier causes \fBpcretest\fR to call PCRE with the PCRE_UTF8
178	option set. This turns on support for UTF-8 character handling in PCRE,
179	provided that it was compiled with this support enabled. This modifier also
180	causes any non-printing characters in output strings to be printed using the
181	\\x{hh...} notation if they are valid UTF-8 sequences.
182
183	.SH CALLOUTS
184	.rs
185	.sp
186	If the pattern contains any callout requests, \fBpcretest\fR's callout function
187	will be called. By default, it displays the callout number, and the start and
188	current positions in the text at the callout time. For example, the output
189
190	--->pqrabcdef
191	0 ^ ^
192
193	indicates that callout number 0 occurred for a match attempt starting at the
194	fourth character of the subject string, when the pointer was at the seventh
195	character. The callout function returns zero (carry on matching) by default.
196
197	Inserting callouts may be helpful when using \fBpcretest\fR to check
198	complicated regular expressions. For further information about callouts, see
199	the
200	.\" HREF
201	\fBpcrecallout\fR
202	.\"
203	documentation.
204
205	For testing the PCRE library, additional control of callout behaviour is
206	available via escape sequences in the data, as described in the following
207	section. In particular, it is possible to pass in a number as callout data (the
208	default is zero). If the callout function receives a non-zero number, it
209	returns that value instead of zero.
210
211	.SH DATA LINES
212	.rs
213	.sp
214	Before each data line is passed to \fBpcre_exec()\fR, leading and trailing
215	whitespace is removed, and it is then scanned for \\ escapes. Some of these are
216	pretty esoteric features, intended for checking out some of the more
217	complicated features of PCRE. If you are just testing "ordinary" regular
218	expressions, you probably don't need any of these. The following escapes are
219	recognized:
220
221	\\a alarm (= BEL)
222	\\b backspace
223	\\e escape
224	\\f formfeed
225	\\n newline
226	\\r carriage return
227	\\t tab
228	\\v vertical tab
229	\\nnn octal character (up to 3 octal digits)
230	\\xhh hexadecimal character (up to 2 hex digits)
231	\\x{hh...} hexadecimal character, any number of digits
232	in UTF-8 mode
233	\\A pass the PCRE_ANCHORED option to \fBpcre_exec()\fR
234	\\B pass the PCRE_NOTBOL option to \fBpcre_exec()\fR
235	\\Cdd call pcre_copy_substring() for substring dd
236	after a successful match (any decimal number
237	less than 32)
238	\\Cname call pcre_copy_named_substring() for substring
239	"name" after a successful match (name termin-
240	ated by next non alphanumeric character)
241	\\C+ show the current captured substrings at callout
242	time
243	\\C- do not supply a callout function
244	\\C!n return 1 instead of 0 when callout number n is
245	reached
246	\\C!n!m return 1 instead of 0 when callout number n is
247	reached for the nth time
248	\\C*n pass the number n (may be negative) as callout
249	data
250	\\Gdd call pcre_get_substring() for substring dd
251	after a successful match (any decimal number
252	less than 32)
253	\\Gname call pcre_get_named_substring() for substring
254	"name" after a successful match (name termin-
255	ated by next non-alphanumeric character)
256	\\L call pcre_get_substringlist() after a
257	successful match
258	\\M discover the minimum MATCH_LIMIT setting
259	\\N pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fR
260	\\Odd set the size of the output vector passed to
261	\fBpcre_exec()\fR to dd (any number of decimal
262	digits)
263	\\Z pass the PCRE_NOTEOL option to \fBpcre_exec()\fR
264
265	If \\M is present, \fBpcretest\fR calls \fBpcre_exec()\fR several times, with
266	different values in the \fImatch_limit\fR field of the \fBpcre_extra\fR data
267	structure, until it finds the minimum number that is needed for
268	\fBpcre_exec()\fR to complete. This number is a measure of the amount of
269	recursion and backtracking that takes place, and checking it out can be
270	instructive. For most simple matches, the number is quite small, but for
271	patterns with very large numbers of matching possibilities, it can become large
272	very quickly with increasing length of subject string.
273
274	When \\O is used, it may be higher or lower than the size set by the \fB-O\fR
275	option (or defaulted to 45); \\O applies only to the call of \fBpcre_exec()\fR
276	for the line in which it appears.
277
278	A backslash followed by anything else just escapes the anything else. If the
279	very last character is a backslash, it is ignored. This gives a way of passing
280	an empty line as data, since a real empty line terminates the data input.
281
282	If \fB/P\fR was present on the regex, causing the POSIX wrapper API to be used,
283	only \fB\B\fR, and \fB\Z\fR have any effect, causing REG_NOTBOL and REG_NOTEOL
284	to be passed to \fBregexec()\fR respectively.
285
286	The use of \\x{hh...} to represent UTF-8 characters is not dependent on the use
287	of the \fB/8\fR modifier on the pattern. It is recognized always. There may be
288	any number of hexadecimal digits inside the braces. The result is from one to
289	six bytes, encoded according to the UTF-8 rules.
290
291	.SH OUTPUT FROM PCRETEST
292	.rs
293	.sp
294	When a match succeeds, pcretest outputs the list of captured substrings that
295	\fBpcre_exec()\fR returns, starting with number 0 for the string that matched
296	the whole pattern. Here is an example of an interactive pcretest run.
297
298	$ pcretest
299	PCRE version 4.00 08-Jan-2003
300
301	re> /^abc(\\d+)/
302	data> abc123
303	0: abc123
304	1: 123
305	data> xyz
306	No match
307
308	If the strings contain any non-printing characters, they are output as \\0x
309	escapes, or as \\x{...} escapes if the \fB/8\fR modifier was present on the
310	pattern. If the pattern has the \fB/+\fR modifier, then the output for
311	substring 0 is followed by the the rest of the subject string, identified by
312	"0+" like this:
313
314	re> /cat/+
315	data> cataract
316	0: cat
317	0+ aract
318
319	If the pattern has the \fB/g\fR or \fB/G\fR modifier, the results of successive
320	matching attempts are output in sequence, like this:
321
322	re> /\\Bi(\\w\\w)/g
323	data> Mississippi
324	0: iss
325	1: ss
326	0: iss
327	1: ss
328	0: ipp
329	1: pp
330
331	"No match" is output only if the first match attempt fails.
332
333	If any of the sequences \fB\\C\fR, \fB\\G\fR, or \fB\\L\fR are present in a
334	data line that is successfully matched, the substrings extracted by the
335	convenience functions are output with C, G, or L after the string number
336	instead of a colon. This is in addition to the normal full list. The string
337	length (that is, the return from the extraction function) is given in
338	parentheses after each string for \fB\\C\fR and \fB\\G\fR.
339
340	Note that while patterns can be continued over several lines (a plain ">"
341	prompt is used for continuations), data lines may not. However newlines can be
342	included in data by means of the \\n escape.
343
344	.SH AUTHOR
345	.rs
346	.sp
347	Philip Hazel <ph10@cam.ac.uk>
348	.br
349	University Computing Service,
350	.br
351	Cambridge CB2 3QG, England.
352
353	.in 0
354	Last updated: 03 February 2003
355	.br
356	Copyright (c) 1997-2003 University of Cambridge.