How do I match the closest of repeated strings?

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

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Re: How do I match the closest of repeated strings? by moritz (Cardinal) on Sep 29, 2008 at 08:33 UTC
Something along these lines? `m{ .* # match as late as possible ( ^abc$ # the abc .*? # everything up to ^def$ # the def ) }smx` [download] Untested, and will be confused if there are mulitple `def` lines. In that case it helps to tokenize the input first (for example reading line by line)	[reply] [d/l] [select]
Re^2: How do I match the closest of repeated strings? by Anonymous Monk on Sep 29, 2008 at 09:27 UTC
Sorry for my reply to the response below. I did not have the initial .* to eliminate the first abc strings. I knew this was straightforward. Sometimes when you get a mental block about something, you just can't figure it out no matter how much you stare at it. Thanks to both of you.	[reply]
Re: How do I match the closest of repeated strings? by GrandFather (Saint) on Sep 29, 2008 at 08:42 UTC
Why? Very often the specific application makes a big difference to choosing a good solution. Either the solution is fairly trivial (`/.abc(.?)def/sm`) or there is a bunch of context you are not telling us about. Perl reduces RSI - it saves typing	[reply] [d/l]
Re^2: How do I match the closest of repeated strings? by Anonymous Monk on Sep 29, 2008 at 09:19 UTC
I tried that (as it seemed like the obvious thing to do), but it didn't work. I got the match from the first abc up to the def.	[reply]
Re^3: How do I match the closest of repeated strings? by GrandFather (Saint) on Sep 29, 2008 at 20:00 UTC
`'xyz abc 123 abc pqr abc get this bit def ijk abc lmn' =~ /.abc(.?)d +ef/sm; print ">$1<";` [download] Prints: `> get this bit <` [download] which is what I understood you to want. Update: Ah, I see it did do what you want. ;) Perl reduces RSI - it saves typing	[reply] [d/l] [select]
Re: How do I match the closest of repeated strings? by ikegami (Patriarch) on Sep 29, 2008 at 09:37 UTC
Alternative: `m{ ( ^abc$ (?:(?!^def$).)* ^def$ ) }smx` [download]	[reply] [d/l]
Re^2: How do I match the closest of repeated strings? by moritz (Cardinal) on Sep 29, 2008 at 09:50 UTC
That will match everything from the first `abc` to the first `def`, not not everything starting from the closest `abc` (which I believe is what the OP wants). But it can be adapted, of course: `m{ ( ^abc$ (?:(?!^(?:def\|abc)$).)* ^def$ ) }smx` [download]	[reply] [d/l] [select]
Re: How do I match the closest of repeated strings? by graff (Chancellor) on Sep 30, 2008 at 01:53 UTC
Looks like the kind of game where 'paragraph-mode' input would be a good idea: `$/ = ""; # input record separator set to empty string my $last_rec; while (<>) { # each record is terminated by /\n{2,}/ if ( /^def/ ) { print $last_rec.$_ if ( $last_rec ); } else { $last_rec = $_; } }` [download] Check perlvar for more info on $/. UPDATE: Sorry, I probably misunderstood the problem. If blank lines are actually distributed as shown in the OP, then something like this would be needed in order to use "paragraph-based" input: `$/ = ""; my $last_prefix = my $last_target = ''; while (<>) { if ( /^abc/ ) { print $last_prefix.$last_target if ( $last_target ); $last_prefix = $_; $last_target = ''; } elsif ( /^def/ ) { $last_target = $_; } elsif ( $last_target ) { $last_target .= $_; } elsif ( $last_prefix ) { $last_prefix .= $_; } }` [download] That's pretty icky, really -- very sorry. I suggest you just slurp the whole file and use one of the regex solutions from an earlier reply. Another update: I still did not get the OP's intent -- but no point fixing this code, since other solutions are up there (I think). Never mind me.	[reply] [d/l] [select]