UNIX for Dummies Questions & Answers

Hi,

How do i grep unique occurrences from a file.

I have a log file with multiple occurrences of 'foo' for instance. When i do:
grep foo, I get all the lines that contain foo.
Is there any way to get only one line for foo?

Example file:

Code:

foo at 09.01am Fri 11 May 2007
foo at 09.13am Fri 11 May 2007
foo at 09.17am Fri 11 May 2007
boo at 09.00am Fri 11 May 2007

when I do grep foo I get 3 lines. I only need one line (it doesn't matter which one). Is this possible?

Many thanks for your help.

Do you have GNU grep ?

Code:

grep -m 1 needle haystack

Or

Code:

sed -n -e "/foo/p;q" file

Code:

sed -n "/foo/{p;q;}" file

Code:

awk ' /foo/ { print ; exit } ' file

Code:

grep whatever file | head -1

Thanks that does the trick.

Also taking it a bit further is there a way to clean up a file so it only has unique occurrences? Say I don't know the patterns to search for, I just want to remove all duplicates. Is this possible?

Thanks

Code:

awk ' { arr[$1]=$0 } END { for ( key in arr ) { print arr[key] } } ' filename

Code:

sort input_file | uniq