247 lines
10 KiB
Plaintext
247 lines
10 KiB
Plaintext
The pcretest program
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--------------------
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This program is intended for testing PCRE, but it can also be used for
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experimenting with regular expressions.
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If it is given two filename arguments, it reads from the first and writes to
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the second. If it is given only one filename argument, it reads from that file
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and writes to stdout. Otherwise, it reads from stdin and writes to stdout, and
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prompts for each line of input, using "re>" to prompt for regular expressions,
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and "data>" to prompt for data lines.
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The program handles any number of sets of input on a single input file. Each
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set starts with a regular expression, and continues with any number of data
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lines to be matched against the pattern. An empty line signals the end of the
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data lines, at which point a new regular expression is read. The regular
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expressions are given enclosed in any non-alphameric delimiters other than
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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 expression may
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be continued over several input lines, in which case the newline characters are
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included within it. See the test input files in the testdata directory for many
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examples. It is possible to include the delimiter within the pattern by
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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, but since
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delimiters are always non-alphameric, this does not affect its interpretation.
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If the terminating delimiter is immediately followed by a backslash, for
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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 provide a
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way of testing the error condition that arises if a pattern finishes with a
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backslash, because
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/abc\/
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is interpreted as the first line of a pattern that starts with "abc/", causing
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pcretest to read the next line as a continuation of the regular expression.
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PATTERN MODIFIERS
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-----------------
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The pattern may be followed by i, m, s, or x to set the PCRE_CASELESS,
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PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively. For
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example:
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/caseless/i
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These modifier letters have the same effect as they do in Perl. There are
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others which set PCRE options that do not correspond to anything in Perl: /A,
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/E, and /X set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respectively.
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Searching for all possible matches within each subject string can be requested
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by the /g or /G modifier. After finding a match, PCRE is called again to search
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the remainder of the subject string. The difference between /g and /G is that
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the former uses the startoffset argument to pcre_exec() to start searching at
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a new point within the entire string (which is in effect what Perl does),
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whereas the latter passes over a shortened substring. This makes a difference
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to the matching process if the pattern begins with a lookbehind assertion
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(including \b or \B).
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If any call to pcre_exec() in a /g or /G sequence matches an empty string, the
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next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED flags set in order
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to search for another, non-empty, match at the same point. If this second match
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fails, the start offset is advanced by one, and the normal match is retried.
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This imitates the way Perl handles such cases when using the /g modifier or the
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split() function.
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There are a number of other modifiers for controlling the way pcretest
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operates.
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The /+ modifier requests that as well as outputting the substring that matched
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the entire pattern, pcretest should in addition output the remainder of the
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subject string. This is useful for tests where the subject contains multiple
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copies of the same substring.
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The /L modifier must be followed directly by the name of a locale, for example,
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/pattern/Lfr
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For this reason, it must be the last modifier letter. The given locale is set,
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pcre_maketables() is called to build a set of character tables for the locale,
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and this is then passed to pcre_compile() when compiling the regular
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expression. Without an /L modifier, NULL is passed as the tables pointer; that
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is, /L applies only to the expression on which it appears.
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The /I modifier requests that pcretest output information about the compiled
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expression (whether it is anchored, has a fixed first character, and so on). It
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does this by calling pcre_fullinfo() after compiling an expression, and
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outputting the information it gets back. If the pattern is studied, the results
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of that are also output.
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The /D modifier is a PCRE debugging feature, which also assumes /I. It causes
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the internal form of compiled regular expressions to be output after
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compilation.
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The /S modifier causes pcre_study() to be called after the expression has been
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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 compiled
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pattern to be output.
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The /P modifier causes pcretest to call PCRE via the POSIX wrapper API rather
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than its native API. When this is done, all other modifiers except /i, /m, and
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/+ are ignored. REG_ICASE is set if /i is present, and REG_NEWLINE is set if /m
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is present. The wrapper functions force PCRE_DOLLAR_ENDONLY always, and
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PCRE_DOTALL unless REG_NEWLINE is set.
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The /8 modifier causes pcretest to call PCRE with the PCRE_UTF8 option set.
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This turns on the (currently incomplete) support for UTF-8 character handling
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in PCRE, provided 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 using
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the \x{hh...} notation if they are valid UTF-8 sequences.
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DATA LINES
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----------
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Before each data line is passed to pcre_exec(), leading and trailing whitespace
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is removed, and it is then scanned for \ escapes. The following 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 UTF-8 character
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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 after a successful
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match (any decimal number less than 32)
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\Gdd call pcre_get_substring() for substring dd after a successful
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match (any decimal number less than 32)
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\L call pcre_get_substringlist() after a successful match
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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 pcre_exec() to dd
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(any number of decimal digits)
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\Z pass the PCRE_NOTEOL option to pcre_exec()
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A backslash followed by anything else just escapes the anything else. If the
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very last character is a backslash, it is ignored. This gives a way of passing
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an empty line as data, since a real empty line terminates the data input.
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If /P was present on the regex, causing the POSIX wrapper API to be used, only
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\B, and \Z have any effect, causing REG_NOTBOL and REG_NOTEOL to be passed to
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regexec() respectively.
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The use of \x{hh...} to represent UTF-8 characters is not dependent on the use
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of the /8 modifier on the pattern. It is recognized always. There may be any
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number of hexadecimal digits inside the braces. The result is from one to six
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bytes, encoded according to the UTF-8 rules.
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OUTPUT FROM PCRETEST
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--------------------
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When a match succeeds, pcretest outputs the list of captured substrings that
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pcre_exec() returns, starting with number 0 for the string that matched the
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whole pattern. Here is an example of an interactive pcretest run.
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$ pcretest
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PCRE version 2.06 08-Jun-1999
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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 \0x
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escapes, or as \x{...} escapes if the /8 modifier was present on the pattern.
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If the pattern has the /+ modifier, then the output for substring 0 is followed
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by the the rest of the subject string, identified 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 matching
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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 \C, \G, or \L are present in a data line that is successfully
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matched, the substrings extracted by the convenience functions are output with
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C, G, or L after the string number instead of a colon. This is in addition to
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the normal full list. The string length (that is, the return from the
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extraction function) is given in parentheses 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 newlines can be
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included in data by means of the \n escape.
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COMMAND LINE OPTIONS
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--------------------
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If the -p option is given to pcretest, it is equivalent to adding /P to each
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regular expression: the POSIX wrapper API is used to call PCRE. None of the
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following flags has any effect in this case.
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If the option -d is given to pcretest, it is equivalent to adding /D to each
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regular expression: the internal form is output after compilation.
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If the option -i is given to pcretest, it is equivalent to adding /I to each
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regular expression: information about the compiled pattern is given after
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compilation.
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If the option -m is given to pcretest, it outputs the size of each compiled
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pattern after it has been compiled. It is equivalent to adding /M to each
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regular expression. For compatibility with earlier versions of pcretest, -s is
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a synonym for -m.
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If the -t option is given, each compile, study, and match is run 20000 times
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while being timed, and the resulting time per compile or match is output in
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milliseconds. Do not set -t with -m, because you will then get the size output
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20000 times and the timing will be distorted. If you want to change the number
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of repetitions used for timing, edit the definition of LOOPREPEAT at the top of
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pcretest.c
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Philip Hazel <ph10@cam.ac.uk>
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August 2000
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