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PCRETEST(1) PCRETEST(1)
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NAME
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pcretest - a program for testing Perl-compatible regular expressions.
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SYNOPSIS
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pcretest [-C] [-d] [-dfa] [-i] [-m] [-o osize] [-p] [-t] [source]
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[destination]
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pcretest was written as a test program for the PCRE regular expression
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library itself, but it can also be used for experimenting with regular
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expressions. This document describes the features of the test program;
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for details of the regular expressions themselves, see the pcrepattern
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documentation. For details of the PCRE library function calls and their
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options, see the pcreapi documentation.
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OPTIONS
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-C Output the version number of the PCRE library, and all avail-
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able information about the optional features that are
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included, and then exit.
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-d Behave as if each regex has the /D (debug) modifier; the
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internal form is output after compilation.
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-dfa Behave as if each data line contains the \D escape sequence;
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this causes the alternative matching function,
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pcre_dfa_exec(), to be used instead of the standard
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pcre_exec() function (more detail is given below).
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-i Behave as if each regex has the /I modifier; information
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about the compiled pattern is given after compilation.
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-m Output the size of each compiled pattern after it has been
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compiled. This is equivalent to adding /M to each regular
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expression. For compatibility with earlier versions of
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pcretest, -s is a synonym for -m.
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-o osize Set the number of elements in the output vector that is used
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when calling pcre_exec() to be osize. The default value is
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45, which is enough for 14 capturing subexpressions. The vec-
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tor size can be changed for individual matching calls by
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including \O in the data line (see below).
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-p Behave as if each regex has the /P modifier; the POSIX wrap-
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per API is used to call PCRE. None of the other options has
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any effect when -p is set.
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-t Run each compile, study, and match many times with a timer,
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and output resulting time per compile or match (in millisec-
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onds). Do not set -m with -t, because you will then get the
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size output a zillion times, and the timing will be dis-
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torted.
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DESCRIPTION
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If pcretest is given two filename arguments, it reads from the first
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and writes to the second. If it is given only one filename argument, it
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reads from that file and writes to stdout. Otherwise, it reads from
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stdin and writes to stdout, and prompts for each line of input, using
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"re>" to prompt for regular expressions, and "data>" to prompt for data
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lines.
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The program handles any number of sets of input on a single input file.
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Each set starts with a regular expression, and continues with any num-
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ber of data lines to be matched against the pattern.
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Each data line is matched separately and independently. If you want to
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do multiple-line matches, you have to use the \n escape sequence in a
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single line of input to encode the newline characters. The maximum
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length of data line is 30,000 characters.
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An empty line signals the end of the data lines, at which point a new
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regular expression is read. The regular expressions are given enclosed
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in any non-alphanumeric delimiters other than backslash, for example
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/(a|bc)x+yz/
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White space before the initial delimiter is ignored. A regular expres-
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sion may be continued over several input lines, in which case the new-
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line characters are included within it. It is possible to include the
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delimiter within the pattern by escaping it, for example
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/abc\/def/
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If you do so, the escape and the delimiter form part of the pattern,
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but since delimiters are always non-alphanumeric, this does not affect
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its interpretation. If the terminating delimiter is immediately fol-
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lowed by a backslash, for example,
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/abc/\
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then a backslash is added to the end of the pattern. This is done to
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provide a way of testing the error condition that arises if a pattern
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finishes with a backslash, because
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/abc\/
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is interpreted as the first line of a pattern that starts with "abc/",
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causing pcretest to read the next line as a continuation of the regular
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expression.
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PATTERN MODIFIERS
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A pattern may be followed by any number of modifiers, which are mostly
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single characters. Following Perl usage, these are referred to below
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as, for example, "the /i modifier", even though the delimiter of the
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pattern need not always be a slash, and no slash is used when writing
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modifiers. Whitespace may appear between the final pattern delimiter
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and the first modifier, and between the modifiers themselves.
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The /i, /m, /s, and /x modifiers set the PCRE_CASELESS, PCRE_MULTILINE,
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PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when pcre_com-
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pile() is called. These four modifier letters have the same effect as
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they do in Perl. For example:
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/caseless/i
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The following table shows additional modifiers for setting PCRE options
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that do not correspond to anything in Perl:
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/A PCRE_ANCHORED
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/C PCRE_AUTO_CALLOUT
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/E PCRE_DOLLAR_ENDONLY
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/f PCRE_FIRSTLINE
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/N PCRE_NO_AUTO_CAPTURE
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/U PCRE_UNGREEDY
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/X PCRE_EXTRA
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Searching for all possible matches within each subject string can be
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requested by the /g or /G modifier. After finding a match, PCRE is
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called again to search the remainder of the subject string. The differ-
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ence between /g and /G is that the former uses the startoffset argument
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to pcre_exec() to start searching at a new point within the entire
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string (which is in effect what Perl does), whereas the latter passes
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over a shortened substring. This makes a difference to the matching
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process if the pattern begins with a lookbehind assertion (including \b
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or \B).
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If any call to pcre_exec() in a /g or /G sequence matches an empty
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string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED
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flags set in order to search for another, non-empty, match at the same
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point. If this second match fails, the start offset is advanced by
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one, and the normal match is retried. This imitates the way Perl han-
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dles such cases when using the /g modifier or the split() function.
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There are yet more modifiers for controlling the way pcretest operates.
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The /+ modifier requests that as well as outputting the substring that
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matched the entire pattern, pcretest should in addition output the
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remainder of the subject string. This is useful for tests where the
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subject contains multiple copies of the same substring.
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The /L modifier must be followed directly by the name of a locale, for
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example,
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/pattern/Lfr_FR
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For this reason, it must be the last modifier. The given locale is set,
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pcre_maketables() is called to build a set of character tables for the
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locale, and this is then passed to pcre_compile() when compiling the
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regular expression. Without an /L modifier, NULL is passed as the
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tables pointer; that is, /L applies only to the expression on which it
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appears.
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The /I modifier requests that pcretest output information about the
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compiled pattern (whether it is anchored, has a fixed first character,
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and so on). It does this by calling pcre_fullinfo() after compiling a
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pattern. If the pattern is studied, the results of that are also out-
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put.
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The /D modifier is a PCRE debugging feature, which also assumes /I. It
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causes the internal form of compiled regular expressions to be output
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after compilation. If the pattern was studied, the information returned
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is also output.
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The /F modifier causes pcretest to flip the byte order of the fields in
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the compiled pattern that contain 2-byte and 4-byte numbers. This
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facility is for testing the feature in PCRE that allows it to execute
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patterns that were compiled on a host with a different endianness. This
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feature is not available when the POSIX interface to PCRE is being
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used, that is, when the /P pattern modifier is specified. See also the
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section about saving and reloading compiled patterns below.
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The /S modifier causes pcre_study() to be called after the expression
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has been compiled, and the results used when the expression is matched.
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The /M modifier causes the size of memory block used to hold the com-
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piled pattern to be output.
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The /P modifier causes pcretest to call PCRE via the POSIX wrapper API
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rather than its native API. When this is done, all other modifiers
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except /i, /m, and /+ are ignored. REG_ICASE is set if /i is present,
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and REG_NEWLINE is set if /m is present. The wrapper functions force
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PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set.
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The /8 modifier causes pcretest to call PCRE with the PCRE_UTF8 option
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set. This turns on support for UTF-8 character handling in PCRE, pro-
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vided that it was compiled with this support enabled. This modifier
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also causes any non-printing characters in output strings to be printed
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using the \x{hh...} notation if they are valid UTF-8 sequences.
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If the /? modifier is used with /8, it causes pcretest to call
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pcre_compile() with the PCRE_NO_UTF8_CHECK option, to suppress the
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checking of the string for UTF-8 validity.
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DATA LINES
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Before each data line is passed to pcre_exec(), leading and trailing
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whitespace is removed, and it is then scanned for \ escapes. Some of
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these are pretty esoteric features, intended for checking out some of
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the more complicated features of PCRE. If you are just testing "ordi-
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nary" regular expressions, you probably don't need any of these. The
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following escapes are recognized:
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\a alarm (= BEL)
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\b backspace
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\e escape
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\f formfeed
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\n newline
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\r carriage return
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\t tab
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\v vertical tab
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\nnn octal character (up to 3 octal digits)
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\xhh hexadecimal character (up to 2 hex digits)
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\x{hh...} hexadecimal character, any number of digits
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in UTF-8 mode
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\A pass the PCRE_ANCHORED option to pcre_exec()
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\B pass the PCRE_NOTBOL option to pcre_exec()
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\Cdd call pcre_copy_substring() for substring dd
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after a successful match (number less than 32)
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\Cname call pcre_copy_named_substring() for substring
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"name" after a successful match (name termin-
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ated by next non alphanumeric character)
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\C+ show the current captured substrings at callout
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time
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\C- do not supply a callout function
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\C!n return 1 instead of 0 when callout number n is
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reached
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\C!n!m return 1 instead of 0 when callout number n is
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reached for the nth time
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\C*n pass the number n (may be negative) as callout
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data; this is used as the callout return value
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\D use the pcre_dfa_exec() match function
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\F only shortest match for pcre_dfa_exec()
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\Gdd call pcre_get_substring() for substring dd
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after a successful match (number less than 32)
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\Gname call pcre_get_named_substring() for substring
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"name" after a successful match (name termin-
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ated by next non-alphanumeric character)
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\L call pcre_get_substringlist() after a
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successful match
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\M discover the minimum MATCH_LIMIT setting
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\N pass the PCRE_NOTEMPTY option to pcre_exec()
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\Odd set the size of the output vector passed to
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pcre_exec() to dd (any number of digits)
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\P pass the PCRE_PARTIAL option to pcre_exec()
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or pcre_dfa_exec()
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\R pass the PCRE_DFA_RESTART option to pcre_dfa_exec()
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\S output details of memory get/free calls during matching
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\Z pass the PCRE_NOTEOL option to pcre_exec()
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\? pass the PCRE_NO_UTF8_CHECK option to
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pcre_exec()
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\>dd start the match at offset dd (any number of digits);
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this sets the startoffset argument for pcre_exec()
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A backslash followed by anything else just escapes the anything else.
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If the very last character is a backslash, it is ignored. This gives a
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way of passing an empty line as data, since a real empty line termi-
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nates the data input.
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If \M is present, pcretest calls pcre_exec() several times, with dif-
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ferent values in the match_limit field of the pcre_extra data struc-
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ture, until it finds the minimum number that is needed for pcre_exec()
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to complete. This number is a measure of the amount of recursion and
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backtracking that takes place, and checking it out can be instructive.
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For most simple matches, the number is quite small, but for patterns
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with very large numbers of matching possibilities, it can become large
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very quickly with increasing length of subject string.
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When \O is used, the value specified may be higher or lower than the
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size set by the -O command line option (or defaulted to 45); \O applies
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only to the call of pcre_exec() for the line in which it appears.
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If the /P modifier was present on the pattern, causing the POSIX wrap-
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per API to be used, only \B and \Z have any effect, causing REG_NOTBOL
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and REG_NOTEOL to be passed to regexec() respectively.
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The use of \x{hh...} to represent UTF-8 characters is not dependent on
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the use of the /8 modifier on the pattern. It is recognized always.
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There may be any number of hexadecimal digits inside the braces. The
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result is from one to six bytes, encoded according to the UTF-8 rules.
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THE ALTERNATIVE MATCHING FUNCTION
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By default, pcretest uses the standard PCRE matching function,
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pcre_exec() to match each data line. From release 6.0, PCRE supports an
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alternative matching function, pcre_dfa_test(), which operates in a
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different way, and has some restrictions. The differences between the
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two functions are described in the pcrematching documentation.
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If a data line contains the \D escape sequence, or if the command line
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contains the -dfa option, the alternative matching function is called.
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This function finds all possible matches at a given point. If, however,
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the \F escape sequence is present in the data line, it stops after the
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first match is found. This is always the shortest possible match.
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DEFAULT OUTPUT FROM PCRETEST
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This section describes the output when the normal matching function,
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pcre_exec(), is being used.
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When a match succeeds, pcretest outputs the list of captured substrings
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that pcre_exec() returns, starting with number 0 for the string that
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matched the whole pattern. Otherwise, it outputs "No match" or "Partial
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match" when pcre_exec() returns PCRE_ERROR_NOMATCH or PCRE_ERROR_PAR-
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TIAL, respectively, and otherwise the PCRE negative error number. Here
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is an example of an interactive pcretest run.
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$ pcretest
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PCRE version 5.00 07-Sep-2004
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re> /^abc(\d+)/
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data> abc123
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0: abc123
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1: 123
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data> xyz
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No match
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If the strings contain any non-printing characters, they are output as
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\0x escapes, or as \x{...} escapes if the /8 modifier was present on
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the pattern. If the pattern has the /+ modifier, the output for sub-
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string 0 is followed by the the rest of the subject string, identified
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by "0+" like this:
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re> /cat/+
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data> cataract
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0: cat
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0+ aract
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If the pattern has the /g or /G modifier, the results of successive
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matching attempts are output in sequence, like this:
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re> /\Bi(\w\w)/g
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data> Mississippi
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0: iss
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1: ss
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0: iss
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1: ss
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0: ipp
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1: pp
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"No match" is output only if the first match attempt fails.
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If any of the sequences \C, \G, or \L are present in a data line that
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is successfully matched, the substrings extracted by the convenience
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functions are output with C, G, or L after the string number instead of
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a colon. This is in addition to the normal full list. The string length
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(that is, the return from the extraction function) is given in paren-
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theses after each string for \C and \G.
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Note that while patterns can be continued over several lines (a plain
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">" prompt is used for continuations), data lines may not. However new-
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lines can be included in data by means of the \n escape.
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OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION
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When the alternative matching function, pcre_dfa_exec(), is used (by
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means of the \D escape sequence or the -dfa command line option), the
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output consists of a list of all the matches that start at the first
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point in the subject where there is at least one match. For example:
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re> /(tang|tangerine|tan)/
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data> yellow tangerine\D
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0: tangerine
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1: tang
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2: tan
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(Using the normal matching function on this data finds only "tang".)
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The longest matching string is always given first (and numbered zero).
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If /gP is present on the pattern, the search for further matches
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resumes at the end of the longest match. For example:
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re> /(tang|tangerine|tan)/g
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data> yellow tangerine and tangy sultana\D
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0: tangerine
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1: tang
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2: tan
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0: tang
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1: tan
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0: tan
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Since the matching function does not support substring capture, the
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escape sequences that are concerned with captured substrings are not
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relevant.
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RESTARTING AFTER A PARTIAL MATCH
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When the alternative matching function has given the PCRE_ERROR_PARTIAL
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return, indicating that the subject partially matched the pattern, you
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can restart the match with additional subject data by means of the \R
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escape sequence. For example:
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re> /^?(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)$/
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data> 23ja\P\D
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Partial match: 23ja
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data> n05\R\D
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0: n05
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For further information about partial matching, see the pcrepartial
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documentation.
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CALLOUTS
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If the pattern contains any callout requests, pcretest's callout func-
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| 429 |
tion is called during matching. This works with both matching func-
|
| 430 |
tions. By default, the called function displays the callout number, the
|
| 431 |
start and current positions in the text at the callout time, and the
|
| 432 |
next pattern item to be tested. For example, the output
|
| 433 |
|
| 434 |
--->pqrabcdef
|
| 435 |
0 ^ ^ \d
|
| 436 |
|
| 437 |
indicates that callout number 0 occurred for a match attempt starting
|
| 438 |
at the fourth character of the subject string, when the pointer was at
|
| 439 |
the seventh character of the data, and when the next pattern item was
|
| 440 |
\d. Just one circumflex is output if the start and current positions
|
| 441 |
are the same.
|
| 442 |
|
| 443 |
Callouts numbered 255 are assumed to be automatic callouts, inserted as
|
| 444 |
a result of the /C pattern modifier. In this case, instead of showing
|
| 445 |
the callout number, the offset in the pattern, preceded by a plus, is
|
| 446 |
output. For example:
|
| 447 |
|
| 448 |
re> /\d?[A-E]\*/C
|
| 449 |
data> E*
|
| 450 |
--->E*
|
| 451 |
+0 ^ \d?
|
| 452 |
+3 ^ [A-E]
|
| 453 |
+8 ^^ \*
|
| 454 |
+10 ^ ^
|
| 455 |
0: E*
|
| 456 |
|
| 457 |
The callout function in pcretest returns zero (carry on matching) by
|
| 458 |
default, but you can use a \C item in a data line (as described above)
|
| 459 |
to change this.
|
| 460 |
|
| 461 |
Inserting callouts can be helpful when using pcretest to check compli-
|
| 462 |
cated regular expressions. For further information about callouts, see
|
| 463 |
the pcrecallout documentation.
|
| 464 |
|
| 465 |
|
| 466 |
SAVING AND RELOADING COMPILED PATTERNS
|
| 467 |
|
| 468 |
The facilities described in this section are not available when the
|
| 469 |
POSIX inteface to PCRE is being used, that is, when the /P pattern mod-
|
| 470 |
ifier is specified.
|
| 471 |
|
| 472 |
When the POSIX interface is not in use, you can cause pcretest to write
|
| 473 |
a compiled pattern to a file, by following the modifiers with > and a
|
| 474 |
file name. For example:
|
| 475 |
|
| 476 |
/pattern/im >/some/file
|
| 477 |
|
| 478 |
See the pcreprecompile documentation for a discussion about saving and
|
| 479 |
re-using compiled patterns.
|
| 480 |
|
| 481 |
The data that is written is binary. The first eight bytes are the
|
| 482 |
length of the compiled pattern data followed by the length of the
|
| 483 |
optional study data, each written as four bytes in big-endian order
|
| 484 |
(most significant byte first). If there is no study data (either the
|
| 485 |
pattern was not studied, or studying did not return any data), the sec-
|
| 486 |
ond length is zero. The lengths are followed by an exact copy of the
|
| 487 |
compiled pattern. If there is additional study data, this follows imme-
|
| 488 |
diately after the compiled pattern. After writing the file, pcretest
|
| 489 |
expects to read a new pattern.
|
| 490 |
|
| 491 |
A saved pattern can be reloaded into pcretest by specifing < and a file
|
| 492 |
name instead of a pattern. The name of the file must not contain a <
|
| 493 |
character, as otherwise pcretest will interpret the line as a pattern
|
| 494 |
delimited by < characters. For example:
|
| 495 |
|
| 496 |
re> </some/file
|
| 497 |
Compiled regex loaded from /some/file
|
| 498 |
No study data
|
| 499 |
|
| 500 |
When the pattern has been loaded, pcretest proceeds to read data lines
|
| 501 |
in the usual way.
|
| 502 |
|
| 503 |
You can copy a file written by pcretest to a different host and reload
|
| 504 |
it there, even if the new host has opposite endianness to the one on
|
| 505 |
which the pattern was compiled. For example, you can compile on an i86
|
| 506 |
machine and run on a SPARC machine.
|
| 507 |
|
| 508 |
File names for saving and reloading can be absolute or relative, but
|
| 509 |
note that the shell facility of expanding a file name that starts with
|
| 510 |
a tilde (~) is not available.
|
| 511 |
|
| 512 |
The ability to save and reload files in pcretest is intended for test-
|
| 513 |
ing and experimentation. It is not intended for production use because
|
| 514 |
only a single pattern can be written to a file. Furthermore, there is
|
| 515 |
no facility for supplying custom character tables for use with a
|
| 516 |
reloaded pattern. If the original pattern was compiled with custom
|
| 517 |
tables, an attempt to match a subject string using a reloaded pattern
|
| 518 |
is likely to cause pcretest to crash. Finally, if you attempt to load
|
| 519 |
a file that is not in the correct format, the result is undefined.
|
| 520 |
|
| 521 |
|
| 522 |
AUTHOR
|
| 523 |
|
| 524 |
Philip Hazel
|
| 525 |
University Computing Service,
|
| 526 |
Cambridge CB2 3QG, England.
|
| 527 |
|
| 528 |
Last updated: 28 February 2005
|
| 529 |
Copyright (c) 1997-2005 University of Cambridge.
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