any way to run grep backwards, i.e. from the end of the file and up?
Solution 1
I think the command that will best help you is tac: http://linux.die.net/man/1/tac
As it states:
tac - concatenate and print files in reverse
So you could pipe it to grep and match nnn number of lines before stopping, or something along those lines.
Solution 2
That's a big file. You should rotate those logs more often.
If tac
is too slow, you could pick a programming language with a seek
command (perl, for instance), then:
- open the file
- seek to the end
- iteratively:
- seek backwards some amount (4K, or larger)
- read that amount of text
- split on newlines, and search for whatever.
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gcb
Updated on September 18, 2022Comments
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gcb over 1 year
I have a 70G+ log file, and i'd like the most recent entries (apache log append new items at the end) that match a pattern. i can either:
run grep | tail
or
run tail | grep
Option 1 will take forever. Option 2 may return nothing, then I will have to increase the count for tail and keep running until I get something.
If I could grep from the last line up to the first, it would be ideal. But I could not find any option on grep's man page.
Is there any trick to do that? either on grep alone or with any other combination of linux tools?
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Daniel B over 9 yearsAre line numbers important?
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