Trey Darley wrote:
> Say you've got a simple ascii text file, say, 250,000 lines long. Let's
> say it's a logfile. Suppose that you wanted to access an arbitrary range
> of lines, say, lines 10,000 - 13,000. One way of doing this is:
>
> <snip>
> sed -n 10000,13000p foobar.txt
> </snip>
>
> Trouble is, the target systems I need to exec this on are ancient and
> don't take very kindly to the io hammering this delivers. Can you suggest
> a better way of achieving this?
>
> As these *are* logs I'm dealing with I have already implemented rotation
> frequency. That helps, but I'm still facing performance issues. I'm
> specifically looking for input as to whether my sed-based approach can be
> improved.
>
> Because of extremely limited network bandwidth pulling the files off the
> wire and processing them on more studly hardware isn't an option. Also, I
> cannot install any binaries on these remote systems. Standard POSIX
> toolkit is all I've got to work with. :-/
>
> Many thanks, y'all!
> --Trey
>
>
Unfortunately, you can't seek based upon line numbers unless the lines
are fixed length. If the lines are fixed length, you could do that and
save a lot of I/O activity.
If the lines are not fixed length you simply have to start at the
beginnig, however with something like awk you could at least end early
so you don't read (cause I/O) for the whole file.
awk 'NR >= 10000 {print}; NR > 13000 {exit}'
Or, there's good old.
head -13000 file | tail -3000
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