Looking at logs from bottom upwards

Question

Is there a linux command or some way to look at logs from bottom up rather than from top towards bottom. I know about tail -n <number of lines>, but is there something that I can actually scroll and go from bottom up?

Answer 1

Some systems have tac, which is a whimsically-named backward cat. Without that, you can still do something like

awk '{print NR ":" $0}' $file | sort -t: -k 1nr,1 | sed 's/^[0-9][0-9]*://'

Answer 2

I think less +G is what you're looking for — it'll load up the file at the end, and you can use the up arrow (or k) to scroll back. Within the viewer, g will take you to the top of the file and G will take you back to the end. And F will scroll to the end and try to keep reading, like tail -f.

Answer 3

The tac command is like a reverse "cat", if that's what you're after.

If you just want to view a file by starting at the bottom, why don't you use an editor or "less"?

Answer 4

You can run less and then use M-> (that's the meta key, usually alt, and the '>' at the same time) to go to the bottom of the file. less supports scrolling.

Answer 5

If you are writing a nagios check the perl module File::ReadBackwards is useful