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How can I match a multi-line regexp?

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Contributed by Anonymous Monk on Jun 13, 2000 at 22:34 UTC
Q&A  > regular expressions


Description:

How do I match something like:

BASKET

OPEC WEEKLY BASKET PRICE RISES TO 28.23 DOLLARS

that is - a single keyword, followed by 2 newlines, followed by a single line of several words terminated by another newline.

Answer: How can I match a multi-line regexp?
contributed by nuance

It's hard to be certain exactly what you're looking for, I'm going to assume that you are looking for a specific keyword and that the text following is fairly free form.

my $keyword = "BASKET"; $data =~ /^($keyword\n\n.+)$/m;

This looks for the keyword followed by two newlines, and whatever else is on that line. It will not match if the line following the two newlines is blank. The m at the end of the pattern specifies multi-line matching i.e. the $ will match before any newline, not just at the end of the string.

This answer assumes that $data contains all of the text you are trying to search, not just a single line.

Answer: How can I match a multi-line regexp?
contributed by athomason

You need to tell the regex engine to treat your scalar as a multiline string with the /m option; otherwise it won't attempt to match across newlines. For instance,

$_ = "bunch of stuff\nwith target\nstring inside"; print "Found" if /target\nstring/m;
Answer: How can I match a multi-line regexp?
contributed by wesal

To overcome the limitation with the quick in-place edit not working on matching the first-line you can remove the -p and do it yourself like:

perl -i.bak -e 'undef $/; $_=<>; s/line1\nline1/new content/g; print' files ..
Answer: How can I match a multi-line regexp?
contributed by markjugg

If you want to do a quick in-place edit of a bunch of files, you can use this syntax:

perl -pi.bak -e 'undef $/; s/line1\nline2/new content/' files ..

This will create ".bak" files for every file it operates on. NOTE that it won't find any matches on the first line. If someone knows another one-liner that also matches on the first line, I'm interested to see it. :)

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