pcretest
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 regular expression
library itself, but it can also be used for experimenting with regular
expressions. This man page describes the features of the test program;
for details of the regular expressions themselves, see the pcre man
page.
OPTIONS
-d Behave as if each regex had the /D modifier (see below); the
internal form is output after compilation.
-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 compatibility 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 capturing subexpressions. The vector size
can be changed for individual matching calls by including \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 20000 times with a timer,
and output resulting time per compile or match (in millisec-
onds). Do not set -t with -m, because you will then get the
size output 20000 times and the timing will be distorted.
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 single input file.
Each set starts with a regular expression, and continues with any num-
ber of data lines to be matched against the pattern. An empty line sig-
nals 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 expres-
sion may be continued over several input lines, in which case the new-
line 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 fol-
lowed 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 which set PCRE options that do not correspond to anything in
Perl: /A, /E, and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, 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 differ-
ence 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 han-
dles 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 multiple 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 compil-
ing 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 charac-
ter, and so on). It does this by calling pcre_fullinfo() after compil-
ing 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 regular expressions to be output
after compilation.
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 com-
piled 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 the (currently incomplete) support for UTF-8 charac-
ter handling in PCRE, provided that it was compiled with this support
enabled. This modifier also causes any non-printing characters in out-
put strings to be printed using the \x{hh...} notation if they are
valid UTF-8 sequences.
DATA LINES
Before each data line is passed to pcre_exec(), leading and trailing
whitespace is removed, and it is then scanned for \ escapes. The fol-
lowing 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 UTF-8 character
\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 number
less than 32)
\Gdd call pcre_get_substring() for substring dd
after a successful match (any decimal number
less than 32)
\L call pcre_get_substringlist() after a
successful match
\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)
\Z pass the PCRE_NOTEOL option to pcre_exec()
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 termi-
nates 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 hexadecimal 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 captured 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 2.06 08-Jun-1999
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 followed by the the rest of the subject string, identi-
fied 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 paren-
theses 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 new-
lines can be included in data by means of the \n escape.
AUTHOR
Philip Hazel <ph10@cam.ac.uk>
University Computing Service,
New Museums Site,
Cambridge CB2 3QG, England.
Phone: +44 1223 334714
Last updated: 15 August 2001
Copyright (c) 1997-2001 University of Cambridge.
PCRETEST(1)
