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PCRETEST(1) PCRETEST(1)
NAME
pcretest - a program for testing Perl-compatible regular
expressions.
SYNOPSIS
pcretest [-d] [-i] [-m] [-o osize] [-p] [-t] [source]
[destination]
pcretest was written as a test program for the PCRE regu-
lar 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 pcrepattern
documentation. For details of PCRE and its options, see
the pcreapi documentation.
OPTIONS
-C Output the version number of the PCRE library,
and all available information about the optional
features that are included, and then exit.
-d Behave as if each regex had the /D modifier (see
below); the internal form is output after compi-
lation.
-i Behave as if each regex had the /I modifier;
information about the compiled pattern is given
after compilation.
-m Output the size of each compiled pattern after
it has been compiled. This is equivalent to
adding /M to each regular expression. For com-
patibility with earlier versions of pcretest, -s
is a synonym for -m.
-o osize Set the number of elements in the output vector
that is used when calling PCRE to be osize. The
default value is 45, which is enough for 14 cap-
turing subexpressions. The vector size can be
changed for individual matching calls by includ-
ing \O in the data line (see below).
-p Behave as if each regex has /P modifier; the
POSIX wrapper API is used to call PCRE. None of
the other options has any effect when -p is set.
-t Run each compile, study, and match many times
with a timer, and output resulting time per com-
pile or match (in milliseconds). Do not set -t
with -m, because you will then get the size out-
put 20000 times and the timing will be dis-
torted.
DESCRIPTION
If pcretest 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 sin-
gle 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.
PATTERN MODIFIERS
The pattern may be followed by i, m, s, or x 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: /A, /E, /N, /U, and /X 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 /g or /G modifier. After
finding a match, PCRE is called again to search the
remainder of the subject string. The difference between /g
and /G is that the former uses the startoffset argument to
pcre_exec() 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 pcre_exec() in a /g or /G 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 /g modifier or
the split() function.
There are a number of other modifiers for controlling the
way pcretest operates.
The /+ 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 multi-
ple copies of the same substring.
The /L 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, pcre_maketables() is called to build
a set of character tables for the locale, and this is then
passed to pcre_compile() when compiling the regular
expression. Without an /L modifier, NULL is passed as the
tables pointer; that is, /L applies only to the expression
on which it appears.
The /I modifier requests that pcretest output information
about the compiled expression (whether it is anchored, has
a fixed first character, and so on). It does this by call-
ing pcre_fullinfo() after compiling an expression, and
outputting the information it gets back. If the pattern is
studied, the results of that are also output.
The /D modifier is a PCRE debugging feature, which also
assumes /I. It causes the internal form of compiled regu-
lar expressions to be output after compilation. If the
pattern was studied, the information returned is also out-
put.
The /S modifier causes pcre_study() to be called after the
expression has been compiled, and the results used when
the expression is matched.
The /M modifier causes the size of memory block used to
hold the compiled pattern to be output.
The /P modifier causes pcretest to call PCRE via the POSIX
wrapper API rather than its native API. When this is done,
all other modifiers except /i, /m, and /+ are ignored.
REG_ICASE is set if /i is present, and REG_NEWLINE is set
if /m is present. The wrapper functions force
PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless
REG_NEWLINE is set.
The /8 modifier causes pcretest 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 /? modifier is used with /8, it causes pcretest to
call pcre_compile() with the PCRE_NO_UTF8_CHECK option, to
suppress the checking of the string for UTF-8 validity.
CALLOUTS
If the pattern contains any callout requests, pcretest'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 pcretest to
check complicated regular expressions. For further infor-
mation about callouts, see the pcrecallout documentation.
For testing the PCRE library, additional control of call-
out behaviour is available via escape sequences in the
data, as described in the following section. In particu-
lar, 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.
DATA LINES
Before each data line is passed to pcre_exec(), 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" regu-
lar 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 pcre_exec()
\B pass the PCRE_NOTBOL option to pcre_exec()
\Cdd call pcre_copy_substring() for substring dd
after a successful match (any decimal num-
ber
less than 32)
\Cname call pcre_copy_named_substring() for sub-
string
"name" after a successful match (name ter-
min-
ated by next non alphanumeric character)
\C+ show the current captured substrings at call-
out
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 call-
out
data
\Gdd call pcre_get_substring() for substring dd
after a successful match (any decimal num-
ber
less than 32)
\Gname call pcre_get_named_substring() for substring
"name" after a successful match (name ter-
min-
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 pcre_exec()
\Odd set the size of the output vector passed to
pcre_exec() to dd (any number of decimal
digits)
\S output details of memory get/free calls dur-
ing matching
\Z pass the PCRE_NOTEOL option to pcre_exec()
\? pass the PCRE_NO_UTF8_CHECK option to
pcre_exec()
If \M is present, pcretest calls pcre_exec() several
times, with different values in the match_limit field of
the pcre_extra data structure, until it finds the minimum
number that is needed for pcre_exec() to complete. This
number is a measure of the amount of recursion and back-
tracking 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 match-
ing 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 -O option (or defaulted to 45); \O applies only
to the call of pcre_exec() 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 /P was present on the regex, causing the POSIX wrapper
API to be used, only 0 causing REG_NOTBOL and REG_NOTEOL
to be passed to regexec() respectively.
The use of \x{hh...} to represent UTF-8 characters is not
dependent on the use of the /8 modifier on the pattern. It
is recognized always. There may be any number of hexadeci-
mal digits inside the braces. The result is from one to
six bytes, encoded according to the UTF-8 rules.
OUTPUT FROM PCRETEST
When a match succeeds, pcretest outputs the list of cap-
tured substrings that pcre_exec() 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 /8
modifier was present on the pattern. If the pattern has
the /+ modifier, then the output for substring 0 is fol-
lowed 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 /g or /G 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 \C, \G, or \L 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 \C and \G.
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.
AUTHOR
Philip Hazel
University Computing Service,
Cambridge CB2 3QG, England.
Last updated: 09 December 2003
Copyright (c) 1997-2003 University of Cambridge.
PCRETEST(1)