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grep for a line then return lines above

 
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# 1  
Old 03-05-2007
grep for a line then return lines above
Hey guys,

I just want to grep for a line then return a few lines above it I can't seem to find what im looking for on google can someone help me out?

This is on Solaris 9.....

I don't have GNU grep so -B and -A commands will not work
Last edited by kingdbag; 03-05-2007 at 06:01 PM..
# 2  
Old 03-05-2007
Grab GNU grep from sunfreeware.com

http://www.sunfreeware.com/programlistsparc9.html#grep

You can try something like this although it's convoluted.

Cheers
ZB
# 3  
Old 03-05-2007
Wow, do i really need to script something for grep to do this?

I found this and its supposed to return the above 3 lines when it finds FORWARD in the text file and it is blank...

sed -n '/FORWARD/{g;3!p;};h' crap.txt
Last edited by kingdbag; 03-05-2007 at 06:42 PM..
# 4  
Old 03-05-2007
Quote:
Originally Posted by kingdbag
Hey guys,

I just want to grep for a line then return a few lines above it I can't seem to find what im looking for on google can someone help me out?

This is on Solaris 9.....

I don't have GNU grep so -B and -A commands will not work
Code:
pattern=$1
num=$2
shift
nawk -v pattern="$pattern" -v num="$num" '
                       { x[NR % num] = $0 }
  index( $0, pattern ) {
                 n = NR % num
                 top = n + num
                 while ( n++ < top ) print x[n % num]
               }'

I have used nawk, since the default Solaris awk is a version which has been obsolete for almost 20 years.
More recent versions on Solaris, include nawk and /usr/xpg4/bin/awk.

The above version only handles strings, not regular expressions. The following one deals with regexps, but will duplicate lines if there is an overlap. (I may fix that if I have a moment or to, or perhaps someone else can do it.)

Code:
pattern=$1
num=$2
shift
nawk -v num=$num '
                       { x[NR % num] = $0 }
  /'"$pattern"'/ {
                 n = NR % num
                 top = n + num
                 while ( n++ < top ) print x[n % num]
               }'

 
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