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Answer: How do I extract all text between two keywords like start and end?

by chromatic (Archbishop)
on Apr 14, 2000 at 19:41 UTC ( #7636=categorized answer: print w/replies, xml ) Need Help??

Q&A > regular expressions > How do I extract all text between two keywords like start and end? - Answer contributed by chromatic

The basic regexp is:
if ($text =~ /\bstart\b(.*?)\bend\b/) { $result = $1; # do something with results }
Note that the . character matches any character but a newline (see m// if you want to span lines), the * means match zero or more times, and the ? forces * to match as few times as possible -- so it will pick up the first end instead of the last one. The \b is in there to prevent mismatches on words like 'starting' and 'backend'.

It has the limitation of not catching nested starts and ends, in which case you might go the recursion route, and write this as a function:

sub between { my $text = shift; if ($text =~ /start(.*?)end/) { $result = $1; between($result); } else { return $text; } }
That can become prohibitively expensive, depending on your data set. I suspect there's a more hideous solution involving split and join, but that's likely to be counterproductive at this point. It also depends on having balanced tags -- if you don't, don't do this!

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[Corion]: As for somebody hosting national conferences, we don't always know the kind of connectors and aspect ratios available ;)
[ambrus]: Corion: well sure, but that's the similar to any printed document, and the margin is diminishing with today's technology. Video games no longer have to assume that the CRTs won't show the edges of the screen.
[Corion]: If you cram your slides with that much information, they might work in an "offline" situation but not very well for a live presentation IMO
[ambrus]: Corion: in that case I also ask the people who rent the conference rooms to tell conference organizers about the available tech.
[Corion]: ambrus: No, you're misunderstanding. If you place content too far on the left/right/top/ bottom, people might not see it because the view is obstructed ;)(
[Corion]: In Amsterdam, the screen went down to the bottom of the stage (60cm above ground) and the seating was on the ground, meaning that the rows in the back couldn't see the bottom of slides.
[Corion]: There also were some columns that meant that maybe you couldn't see the left/right edge of a slide.
[ambrus]: Corion: Sure. I've had a course in a 50 seat lecture hall that has two fucking columns in the middle.
[Corion]: Talking about it, the top should be fairly visible in the situations I've experienced at least. The top is uncomfortable for people in the first three rows, but that's life ;)
[ambrus]: The pillars are there because this is in the 6th floor of building R of BME, which is an attic that was built in after the original building, which is also why the elevator doesn't go that high and the windows are tiny.

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