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Pattern matching in file and then display 10 lines above every time


 
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# 1  
Old 01-29-2008
Pattern matching in file and then display 10 lines above every time

hiii,

i have to write a shell script like this----

i have a huge log file name abc.log .i have to search for a pattern name "pattern",it may occur 1000 times in the log file,every time it finds the pattern it should display the 10 lines above the pattern.
I appericiate your help.
# 2  
Old 01-29-2008
Quote:
Originally Posted by namishtiwari
hiii,

i have to write a shell script like this----

i have a huge log file name abc.log .i have to search for a pattern name "pattern",it may occur 1000 times in the log file,every time it finds the pattern it should display the 10 lines above the pattern.
I appericiate your help.

Code:
 grep -B 10 ĘpatternĘ file

# 3  
Old 01-29-2008
Quote:
Originally Posted by mirusnet
Code:
 grep -B 10 ĘpatternĘ file

It's telling illegal option -B;I am using HP-UX.
# 4  
Old 01-29-2008
Most Linux grep version supports that option,i guess other dont do,

I have the script to do the job,
Code:
#!/bin/ksh
Usage() {
 echo " mygrep pat files.."
 exit
}

(( $# < 2 )) && Usage

Leading=10

PAT=$1
shift;
FileList=$@

for FileName in ${FileList} ; do
  for LineNo in $( grep -n  $PAT $FileName | cut -d":" -f1 )  ; do
     From=$((LineNo-Leading+1))
     sed -n "$From,$LineNo"p $FileName
  done
done

Thanks
Nagarajan G
# 5  
Old 01-30-2008
Hi.

If I understand the problem and the solution from ennstate, then sed will be loaded up 1000 times. Here is an alternate solution. The attachment is a perl script, pvg (perl version of grep, very limited edition). Assuming that you have perl, this will do simple matching and it will also do the "-B n" behavior of GNU grep. This can then be called once to process the log file. (Get the attachment, rename it to "pvg", then run the test script.) Execute "./pvg -h" for a help page.

Here's a test script:
Code:
#!/bin/bash -

# @(#) s3       Demonstrate printing of text before a matched line.

echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version =o $(_eat $0 $1)

P=./pvg

echo
echo " Input file data3:"
cat data3

echo
echo " Looking for d, normal search:"
$P d data3

echo
echo " Looking for d, print previous 2:"
$P -B 2 d data3

echo
echo " Looking for d, print previous 2, separator:"
$P -s '     ----- \n' -B 2 d data3

echo
echo " Looking for ask, print previous 100, quiet:"
$P -q -B 100 ask data3

exit 0

Producing:
Code:
% ./s3
(Versions displayed with local utility "version")
Linux 2.6.11-x1
GNU bash 2.05b.0

 Input file data3:
     1  Alabama AL
     2  Alaska AK
     3  Arizona AZ
     4  Arkansas AR
     5  California CA
     6  Colorado CO
     7  Connecticut CT
     8  Delaware DE
     9  District of Columbia DC
    10  Florida FL

 Looking for d, normal search:
     6  Colorado CO
    10  Florida FL
 ( Lines read: 10; hits: 2 )

 Looking for d, print previous 2:
     4  Arkansas AR
     5  California CA
     6  Colorado CO
     8  Delaware DE
     9  District of Columbia DC
    10  Florida FL
 ( Lines read: 10; hits: 2 )

 Looking for d, print previous 2, separator:
     4  Arkansas AR
     5  California CA
     6  Colorado CO
     -----
     8  Delaware DE
     9  District of Columbia DC
    10  Florida FL
 ( Lines read: 10; hits: 2 )

 Looking for ask, print previous 100, quiet:
     1  Alabama AL
     2  Alaska AK

It can be a lot of work to make sure that perl and friends are installed, but once it's done, then you can use it for many things. Most systems have it already available.

There is also cgrep at freshmeat.net: Project details for cgrep which has a wealth of features. You need to go through a compilation, but it was fairly painless.

Best wishes ... cheers, drl
# 6  
Old 01-30-2008
The English module is known to create inefficiencies in perl programs. See the English man page for details: English - perldoc.perl.org

I am not sure if it affects the code you posted drl but you may want to take a look.
# 7  
Old 01-30-2008
If I was going to use perl I would just use Tie::File, then you can treat the file like an array and use array subscripting to backtrack 10 lines. But he seems to want a shell script so I can't help with that unless calling a perl script is OK.

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