Mark Post wrote:
On Tue, Sep 4, 2007 at 2:21 PM, in message
<[EMAIL PROTECTED]>, "Scully, William P"
<[EMAIL PROTECTED]> wrote:
What's the best technique for trimming a file? IE: I have file
"/var/log/toolarge". What's the fastest technique to discard
- The first 10,000 records?
sed -i -e '1,10000 d' /var/log/toolarge
- The last 10,000 records?
count=$(wc -l /var/log/toolarge | cut -f1 -d" ")
Why is the cut useful?
let start=$count-9999
if [ ${start} -le 1 ]; then
echo start is set to 1
let start=1
fi
sed -i -e "$start,$ d" /var/log/toolarge
Do we want to read the file twice?
Here's a sed line that I picked up someplace (I think there's a site
devoted to sed) and adapted, but don't really understand, It prints a
few, then maintains a hold buffer to the end, and then prints the hold
buffer.
Perhaps it too can be adapted, and do it in one pass.
CPU consumption may be a drawback though.
And as a bonus, since files are stream oriented, what's the fastest
technique for finding out how many records are in the file?
wc -l /var/log/toolarge
--
Cheers
John
-- spambait
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