trunk/doc/pcretest.1

.TH PCRETEST 1
.SH NAME
pcretest - a program for testing Perl-compatible regular expressions.
.SH SYNOPSIS
.rs
.sp
.B pcretest "[-C] [-d] [-dfa] [-i] [-m] [-o osize] [-p] [-t] [source]"
.ti +5n
.B "[destination]"
.P
\fBpcretest\fP 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\fP
.\"
documentation. For details of the PCRE library function calls and their
options, see the
.\" HREF
\fBpcreapi\fP
.\"
documentation.
.
.
.SH OPTIONS
.rs
.TP 10
\fB-C\fP
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\fP
Behave as if each regex has the \fB/D\fP (debug) modifier; the internal
form is output after compilation.
.TP 10
\fB-dfa\fP
Behave as if each data line contains the \eD escape sequence; this causes the
alternative matching function, \fBpcre_dfa_exec()\fP, to be used instead of the
standard \fBpcre_exec()\fP function (more detail is given below).
.TP 10
\fB-i\fP
Behave as if each regex has the \fB/I\fP modifier; information about the
compiled pattern is given after compilation.
.TP 10
\fB-m\fP
Output the size of each compiled pattern after it has been compiled. This is
equivalent to adding \fB/M\fP to each regular expression. For compatibility
with earlier versions of pcretest, \fB-s\fP is a synonym for \fB-m\fP.
.TP 10
\fB-o\fP \fIosize\fP
Set the number of elements in the output vector that is used when calling
\fBpcre_exec()\fP to be \fIosize\fP. The default value is 45, which is enough
for 14 capturing subexpressions. The vector size can be changed for individual
matching calls by including \eO in the data line (see below).
.TP 10
\fB-p\fP
Behave as if each regex has the \fB/P\fP modifier; the POSIX wrapper API is
used to call PCRE. None of the other options has any effect when \fB-p\fP is
set.
.TP 10
\fB-t\fP
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-m\fP with
\fB-t\fP, because you will then get the size output a zillion times, and the
timing will be distorted.
.
.
.SH DESCRIPTION
.rs
.sp
If \fBpcretest\fP 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.
.P
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.
.P
Each data line is matched separately and independently. If you want to do
multiple-line matches, you have to use the \en escape sequence in a single line
of input to encode the newline characters. The maximum length of data line is
30,000 characters.
.P
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-alphanumeric delimiters other than backslash, for example
.sp
  /(a|bc)x+yz/
.sp
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
.sp
  /abc\e/def/
.sp
If you do so, the escape and the delimiter form part of the pattern, but since
delimiters are always non-alphanumeric, this does not affect its interpretation.
If the terminating delimiter is immediately followed by a backslash, for
example,
.sp
  /abc/\e
.sp
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
.sp
  /abc\e/
.sp
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
A pattern may be followed by any number of modifiers, which are mostly single
characters. Following Perl usage, these are referred to below as, for example,
"the \fB/i\fP modifier", even though the delimiter of the pattern need not
always be a slash, and no slash is used when writing modifiers. Whitespace may
appear between the final pattern delimiter and the first modifier, and between
the modifiers themselves.
.P
The \fB/i\fP, \fB/m\fP, \fB/s\fP, and \fB/x\fP modifiers set the PCRE_CASELESS,
PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when
\fBpcre_compile()\fP is called. These four modifier letters have the same
effect as they do in Perl. For example:
.sp
  /caseless/i
.sp
The following table shows additional modifiers for setting PCRE options that do
not correspond to anything in Perl:
.sp
  \fB/A\fP    PCRE_ANCHORED
  \fB/C\fP    PCRE_AUTO_CALLOUT
  \fB/E\fP    PCRE_DOLLAR_ENDONLY
  \fB/f\fP    PCRE_FIRSTLINE
  \fB/N\fP    PCRE_NO_AUTO_CAPTURE
  \fB/U\fP    PCRE_UNGREEDY
  \fB/X\fP    PCRE_EXTRA
.sp
Searching for all possible matches within each subject string can be requested
by the \fB/g\fP or \fB/G\fP modifier. After finding a match, PCRE is called
again to search the remainder of the subject string. The difference between
\fB/g\fP and \fB/G\fP is that the former uses the \fIstartoffset\fP argument to
\fBpcre_exec()\fP 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 \eb or \eB).
.P
If any call to \fBpcre_exec()\fP in a \fB/g\fP or \fB/G\fP 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\fP modifier or the \fBsplit()\fP function.
.P
There are yet more modifiers for controlling the way \fBpcretest\fP
operates.
.P
The \fB/+\fP 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.
.P
The \fB/L\fP modifier must be followed directly by the name of a locale, for
example,
.sp
  /pattern/Lfr_FR
.sp
For this reason, it must be the last modifier. The given locale is set,
\fBpcre_maketables()\fP is called to build a set of character tables for the
locale, and this is then passed to \fBpcre_compile()\fP when compiling the
regular expression. Without an \fB/L\fP modifier, NULL is passed as the tables
pointer; that is, \fB/L\fP applies only to the expression on which it appears.
.P
The \fB/I\fP modifier requests that \fBpcretest\fP output information about the
compiled pattern (whether it is anchored, has a fixed first character, and
so on). It does this by calling \fBpcre_fullinfo()\fP after compiling a
pattern. If the pattern is studied, the results of that are also output.
.P
The \fB/D\fP modifier is a PCRE debugging feature, which also assumes \fB/I\fP.
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.
.P
The \fB/F\fP modifier causes \fBpcretest\fP to flip the byte order of the
fields in the compiled pattern that contain 2-byte and 4-byte numbers. This
facility is for testing the feature in PCRE that allows it to execute patterns
that were compiled on a host with a different endianness. This feature is not
available when the POSIX interface to PCRE is being used, that is, when the
\fB/P\fP pattern modifier is specified. See also the section about saving and
reloading compiled patterns below.
.P
The \fB/S\fP modifier causes \fBpcre_study()\fP to be called after the
expression has been compiled, and the results used when the expression is
matched.
.P
The \fB/M\fP modifier causes the size of memory block used to hold the compiled
pattern to be output.
.P
The \fB/P\fP modifier causes \fBpcretest\fP to call PCRE via the POSIX wrapper
API rather than its native API. When this is done, all other modifiers except
\fB/i\fP, \fB/m\fP, and \fB/+\fP are ignored. REG_ICASE is set if \fB/i\fP is
present, and REG_NEWLINE is set if \fB/m\fP is present. The wrapper functions
force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set.
.P
The \fB/8\fP modifier causes \fBpcretest\fP 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
\ex{hh...} notation if they are valid UTF-8 sequences.
.P
If the \fB/?\fP modifier is used with \fB/8\fP, it causes \fBpcretest\fP to
call \fBpcre_compile()\fP with the PCRE_NO_UTF8_CHECK option, to suppress the
checking of the string for UTF-8 validity.
.
.
.SH "DATA LINES"
.rs
.sp
Before each data line is passed to \fBpcre_exec()\fP, leading and trailing
whitespace is removed, and it is then scanned for \e 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:
.sp
  \ea         alarm (= BEL)
  \eb         backspace
  \ee         escape
  \ef         formfeed
  \en         newline
  \er         carriage return
  \et         tab
  \ev         vertical tab
  \ennn       octal character (up to 3 octal digits)
  \exhh       hexadecimal character (up to 2 hex digits)
.\" JOIN
  \ex{hh...}  hexadecimal character, any number of digits
               in UTF-8 mode
  \eA         pass the PCRE_ANCHORED option to \fBpcre_exec()\fP
  \eB         pass the PCRE_NOTBOL option to \fBpcre_exec()\fP
.\" JOIN
  \eCdd       call pcre_copy_substring() for substring dd
               after a successful match (number less than 32)
.\" JOIN
  \eCname     call pcre_copy_named_substring() for substring
               "name" after a successful match (name termin-
               ated by next non alphanumeric character)
.\" JOIN
  \eC+        show the current captured substrings at callout
               time
  \eC-        do not supply a callout function
.\" JOIN
  \eC!n       return 1 instead of 0 when callout number n is
               reached
.\" JOIN
  \eC!n!m     return 1 instead of 0 when callout number n is
               reached for the nth time
.\" JOIN
  \eC*n       pass the number n (may be negative) as callout
               data; this is used as the callout return value
  \eD         use the \fBpcre_dfa_exec()\fP match function
  \eF         only shortest match for \fBpcre_dfa_exec()\fP
.\" JOIN
  \eGdd       call pcre_get_substring() for substring dd
               after a successful match (number less than 32)
.\" JOIN
  \eGname     call pcre_get_named_substring() for substring
               "name" after a successful match (name termin-
               ated by next non-alphanumeric character)
.\" JOIN
  \eL         call pcre_get_substringlist() after a
               successful match
  \eM         discover the minimum MATCH_LIMIT setting
  \eN         pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fP
.\" JOIN
  \eOdd       set the size of the output vector passed to
               \fBpcre_exec()\fP to dd (any number of digits)
.\" JOIN
  \eP         pass the PCRE_PARTIAL option to \fBpcre_exec()\fP
               or \fBpcre_dfa_exec()\fP
  \eR         pass the PCRE_DFA_RESTART option to \fBpcre_dfa_exec()\fP
  \eS         output details of memory get/free calls during matching
  \eZ         pass the PCRE_NOTEOL option to \fBpcre_exec()\fP
.\" JOIN
  \e?         pass the PCRE_NO_UTF8_CHECK option to
               \fBpcre_exec()\fP
  \e>dd       start the match at offset dd (any number of digits);
               this sets the \fIstartoffset\fP argument for \fBpcre_exec()\fP
.sp
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.
.P
If \eM is present, \fBpcretest\fP calls \fBpcre_exec()\fP several times, with
different values in the \fImatch_limit\fP field of the \fBpcre_extra\fP data
structure, until it finds the minimum number that is needed for
\fBpcre_exec()\fP 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.
.P
When \eO is used, the value specified may be higher or lower than the size set
by the \fB-O\fP command line option (or defaulted to 45); \eO applies only to
the call of \fBpcre_exec()\fP for the line in which it appears.
.P
If the \fB/P\fP modifier was present on the pattern, causing the POSIX wrapper
API to be used, only \eB and \eZ have any effect, causing REG_NOTBOL and
REG_NOTEOL to be passed to \fBregexec()\fP respectively.
.P
The use of \ex{hh...} to represent UTF-8 characters is not dependent on the use
of the \fB/8\fP 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 "THE ALTERNATIVE MATCHING FUNCTION"
.rs
.sp
By default, \fBpcretest\fP uses the standard PCRE matching function,
\fBpcre_exec()\fP to match each data line. From release 6.0, PCRE supports an
alternative matching function, \fBpcre_dfa_test()\fP, which operates in a
different way, and has some restrictions. The differences between the two
functions are described in the
.\" HREF
\fBpcrematching\fP
.\"
documentation.
.P
If a data line contains the \eD escape sequence, or if the command line
contains the \fB-dfa\fP option, the alternative matching function is called.
This function finds all possible matches at a given point. If, however, the \eF
escape sequence is present in the data line, it stops after the first match is
found. This is always the shortest possible match.
.
.
.SH "DEFAULT OUTPUT FROM PCRETEST"
.rs
.sp
This section describes the output when the normal matching function,
\fBpcre_exec()\fP, is being used.
.P
When a match succeeds, pcretest outputs the list of captured substrings that
\fBpcre_exec()\fP returns, starting with number 0 for the string that matched
the whole pattern. Otherwise, it outputs "No match" or "Partial match"
when \fBpcre_exec()\fP returns PCRE_ERROR_NOMATCH or PCRE_ERROR_PARTIAL,
respectively, and otherwise the PCRE negative error number. Here is an example
of an interactive \fBpcretest\fP run.
.sp
  $ pcretest
  PCRE version 5.00 07-Sep-2004
.sp
    re> /^abc(\ed+)/
  data> abc123
   0: abc123
   1: 123
  data> xyz
  No match
.sp
If the strings contain any non-printing characters, they are output as \e0x
escapes, or as \ex{...} escapes if the \fB/8\fP modifier was present on the
pattern. If the pattern has the \fB/+\fP modifier, the output for substring 0
is followed by the the rest of the subject string, identified by "0+" like
this:
.sp
    re> /cat/+
  data> cataract
   0: cat
   0+ aract
.sp
If the pattern has the \fB/g\fP or \fB/G\fP modifier, the results of successive
matching attempts are output in sequence, like this:
.sp
    re> /\eBi(\ew\ew)/g
  data> Mississippi
   0: iss
   1: ss
   0: iss
   1: ss
   0: ipp
   1: pp
.sp
"No match" is output only if the first match attempt fails.
.P
If any of the sequences \fB\eC\fP, \fB\eG\fP, or \fB\eL\fP 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\eC\fP and \fB\eG\fP.
.P
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 \en escape.
.
.
.SH "OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION"
.rs
.sp
When the alternative matching function, \fBpcre_dfa_exec()\fP, is used (by
means of the \eD escape sequence or the \fB-dfa\fP command line option), the
output consists of a list of all the matches that start at the first point in
the subject where there is at least one match. For example:
.sp
    re> /(tang|tangerine|tan)/
  data> yellow tangerine\eD
   0: tangerine
   1: tang
   2: tan
.sp
(Using the normal matching function on this data finds only "tang".) The
longest matching string is always given first (and numbered zero).
.P
If \fB/g\P is present on the pattern, the search for further matches resumes
at the end of the longest match. For example:
.sp
    re> /(tang|tangerine|tan)/g
  data> yellow tangerine and tangy sultana\eD
   0: tangerine
   1: tang
   2: tan
   0: tang
   1: tan
   0: tan
.sp
Since the matching function does not support substring capture, the escape
sequences that are concerned with captured substrings are not relevant.
.
.
.SH "RESTARTING AFTER A PARTIAL MATCH"
.rs
.sp
When the alternative matching function has given the PCRE_ERROR_PARTIAL return,
indicating that the subject partially matched the pattern, you can restart the
match with additional subject data by means of the \eR escape sequence. For
example:
.sp
    re> /^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$/
  data> 23ja\eP\eD
  Partial match: 23ja
  data> n05\eR\eD
   0: n05
.sp
For further information about partial matching, see the
.\" HREF
\fBpcrepartial\fP
.\"
documentation.
.
.
.SH CALLOUTS
.rs
.sp
If the pattern contains any callout requests, \fBpcretest\fP's callout function
is called during matching. This works with both matching functions. By default,
the called function displays the callout number, the start and current
positions in the text at the callout time, and the next pattern item to be
tested. For example, the output
.sp
  --->pqrabcdef
    0    ^  ^     \ed
.sp
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 of the data, and when the next pattern item was \ed. Just one
circumflex is output if the start and current positions are the same.
.P
Callouts numbered 255 are assumed to be automatic callouts, inserted as a
result of the \fB/C\fP pattern modifier. In this case, instead of showing the
callout number, the offset in the pattern, preceded by a plus, is output. For
example:
.sp
    re> /\ed?[A-E]\e*/C
  data> E*
  --->E*
   +0 ^      \ed?
   +3 ^      [A-E]
   +8 ^^     \e*
  +10 ^ ^
   0: E*
.sp
The callout function in \fBpcretest\fP returns zero (carry on matching) by
default, but you can use a \eC item in a data line (as described above) to
change this.
.P
Inserting callouts can be helpful when using \fBpcretest\fP to check
complicated regular expressions. For further information about callouts, see
the
.\" HREF
\fBpcrecallout\fP
.\"
documentation.
.
.
.SH "SAVING AND RELOADING COMPILED PATTERNS"
.rs
.sp
The facilities described in this section are not available when the POSIX
inteface to PCRE is being used, that is, when the \fB/P\fP pattern modifier is
specified.
.P
When the POSIX interface is not in use, you can cause \fBpcretest\fP to write a
compiled pattern to a file, by following the modifiers with > and a file name.
For example:
.sp
  /pattern/im >/some/file
.sp
See the
.\" HREF
\fBpcreprecompile\fP
.\"
documentation for a discussion about saving and re-using compiled patterns.
.P
The data that is written is binary. The first eight bytes are the length of the
compiled pattern data followed by the length of the optional study data, each
written as four bytes in big-endian order (most significant byte first). If
there is no study data (either the pattern was not studied, or studying did not
return any data), the second length is zero. The lengths are followed by an
exact copy of the compiled pattern. If there is additional study data, this
follows immediately after the compiled pattern. After writing the file,
\fBpcretest\fP expects to read a new pattern.
.P
A saved pattern can be reloaded into \fBpcretest\fP by specifing < and a file
name instead of a pattern. The name of the file must not contain a < character,
as otherwise \fBpcretest\fP will interpret the line as a pattern delimited by <
characters.
For example:
.sp
   re> </some/file
  Compiled regex loaded from /some/file
  No study data
.sp
When the pattern has been loaded, \fBpcretest\fP proceeds to read data lines in
the usual way.
.P
You can copy a file written by \fBpcretest\fP to a different host and reload it
there, even if the new host has opposite endianness to the one on which the
pattern was compiled. For example, you can compile on an i86 machine and run on
a SPARC machine.
.P
File names for saving and reloading can be absolute or relative, but note that
the shell facility of expanding a file name that starts with a tilde (~) is not
available.
.P
The ability to save and reload files in \fBpcretest\fP is intended for testing
and experimentation. It is not intended for production use because only a
single pattern can be written to a file. Furthermore, there is no facility for
supplying custom character tables for use with a reloaded pattern. If the
original pattern was compiled with custom tables, an attempt to match a subject
string using a reloaded pattern is likely to cause \fBpcretest\fP to crash.
Finally, if you attempt to load a file that is not in the correct format, the
result is undefined.
.
.
.SH AUTHOR
.rs
.sp
Philip Hazel
.br
University Computing Service,
.br
Cambridge CB2 3QG, England.
.P
.in 0
Last updated: 28 February 2005
.br
Copyright (c) 1997-2005 University of Cambridge.