topic Re: previous line in Operating System - HP-UX

previous line

SAM_24 — Thu, 08 Jan 2004 14:58:38 GMT

Hi,

I want to grep the line which contains word "connected" and print previous line.Any help is appreciated.

Thanks.

Re: previous line

Pete Randall — Thu, 08 Jan 2004 15:03:28 GMT

SAM,

Here's a solution from the "Handy One-Liners for Sed" (attached):

# print 1 line of context before and after regexp, with line number
# indicating where the regexp occurred (similar to "grep -A1 -B1")
sed -n -e '/regexp/{=;x;1!p;g;$!N;p;D;}' -e h

Pete

Re: previous line

Rodney Hills — Thu, 08 Jan 2004 16:12:12 GMT

If you get the GNU grep command, it has an option "-B num" to print "num" lines before each line.

HTH

-- Rod Hills

Re: previous line

Michael Schulte zur Sur — Thu, 08 Jan 2004 16:18:19 GMT

Hi,

something with awk:
BEGIN{ll="no previous line";}
/connect/ {print ll;print $0}
{ll=$0;}
END{}

use awk -f yourname.awk yourfile

greetings,

Michael

Re: previous line

Elmar P. Kolkman — Fri, 09 Jan 2004 02:00:15 GMT

If you want, it can even be done with a shell script:
grep -n connected | cut -d: -f1 | while read number
do
(( number=number-1 ))
sed -n "${number}p"
done

You could even use tail and head to get the line you want.

Re: previous line

Elmar P. Kolkman — Fri, 09 Jan 2004 02:15:37 GMT

Neater solution using shell:
grep -n connected | cut -d: -f1 | while read number
do
(( number=number-1 ))
echo "${number}p"
done | ed -

This way the file is opened twice instead of 1 plus the number of occurrences...