Can I regex & grep to select contiguous lines?

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

I have lines of a file in an array, each begins with a time stamp, HHMMSS, and are in increasing sequential order. How can I construct a grep & regex to select all lines belonging to the 1st 5 minute interval, then the 2nd, 3rd, etc. til end-of-data in array. Thanks!

Originally posted as a Categorized Question.

Comment on Can I regex & grep to select contiguous lines?

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Re: Can I regex & grep to select contiguous lines? by sauoq (Abbot) on Aug 24, 2002 at 20:59 UTC
As your lines are in chronological order anyway, it doesn't make sense to use grep. A grep will search through the whole array but you want a set of contiguous entries and as soon as you find one outside of the right interval you know you are done searching. You would be better off simply iterating through the lines. If seconds don't matter at all, you can just look at the last digit of your minutes and once that digit mod 5 is the same as your starting digit, you are done. If seconds do matter, you'll have to do a little more work but the principle of iterating though the lines instead of grepping still holds.	[reply]
Re: Answer: Can I regex & grep to select contiguous lines? by blakem (Monsignor) on Aug 24, 2002 at 21:13 UTC
once that digit mod 5 is the same as your starting digit, you are done That assumes there is at least one entry for each minute... What if the log looked like: `2:00:00 all is well 2:01:00 all is well 2:02:00 all is well 2:03:00 all is well 2:04:00 oops, reboot 2:21:00 all is well again` [download] I think looking at more than just that one digit is wise. -Blake	[reply] [d/l]


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