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Perl regex help - matching parentheses

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Top Forums Shell Programming and Scripting Perl regex help - matching parentheses
# 8  
Old 02-27-2009
The right answer here is in the perlre of modern perls:

Code:
                 The following pattern matches a parenthesized group:

                   $re = qr{
                              \(
                              (?:
                                 (?> [^()]+ )    # Non-parens without backtracking
                               |
                                 (??{ $re })     # Group with matching parens
                              )*
                              \)
                           }x;

Basically, (??{...}) embeds a regular expression (or a nested expression that chooses a regular expression) within another RE -- getting you recursive regular expressions.

If you have access to perl 5.10, you've got some other approaches available, as 5.10 has true recursive pattern matching without this kind of magic -- see here: perldelta - what is new for perl 5.10.0 - search.cpan.org
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LEARN ABOUT ULTRIX

regex

regex(3)						     Library Functions Manual							  regex(3)

Name
       re_comp, re_exec - regular expression handler

Syntax
       char *re_comp(s)
       char *s;

       re_exec(s)
       char *s;

Description
       The  subroutine	compiles  a string into an internal form suitable for pattern matching.  The subroutine checks the argument string against
       the last string passed to

       The subroutine returns 0 if the string s was compiled successfully; otherwise a string containing an  error  message  is  returned.  If	is
       passed 0 or a null string, it returns without changing the currently compiled regular expression.

       The  subroutine returns 1 if the string s matches the last compiled regular expression, 0 if the string s failed to match the last compiled
       regular expression, and -1 if the compiled regular expression was invalid (indicating an internal error).

       The strings passed to both and may have trailing or embedded newline characters; they are terminated by	nulls.	 The  regular  expressions
       recognized are described in the manual entry for given the above difference.

Diagnostics
       The subroutine returns -1 for an internal error.

       The subroutine returns one of the following strings if an error occurs:

       No previous regular expression
       Regular expression too long
       unmatched (
       missing ]
       too many () pairs
       unmatched )

See Also
       ed(1), ex(1), egrep(1), fgrep(1), grep(1)

																	  regex(3)