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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 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 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 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 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 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 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 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 regu-
lar 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 dif-
ference 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 out-
put after compilation. If the pattern was studied, the information
returned is also output.
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 support for UTF-8 character handling in PCRE, pro-
vided 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 func-
tion 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 compli-
cated regular expressions. For further information about callouts, see
the pcrecallout 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.
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 "ordi-
nary" 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 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)
\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 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 during 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 dif-
ferent values in the match_limit field of the pcre_extra data struc-
ture, 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
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 -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 sub-
strings that pcre_exec() returns, starting with number 0 for the
string that matched the whole pattern. Here is an example of an inter-
active 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 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
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)
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