#!/bin/bash

[[ $# -ne 4 ]] && {

        echo "Usage: $0  pre_patt_numb  post_patt_numb patt filename"
        echo "Usage: $0  2  2 mail /var/adm/messages"
        exit 1
}


pre=$1
post=$2
patt="$3"
fn=$4

[ -f $fn ] || {
        echo "$0: $fn does not exist or insufficent permission"
        exit 1
}

egrep -in "$patt" $fn | awk -F':' ' { print $1 } '  | while read numb
do
        this_pre=`expr $numb - $pre`
        this_post=`expr $numb + $post`
        echo "#_________________ Output of $fn from line ${this_pre} to ${this_post} __________#"
        sed -n ${this_pre},${this_post}p $fn

done

exit 0