#!/bin/bash
#problem: grep gives "memory exhausted" error on 6TB disks
##solution: read it on parts
if [ -z $2 ] || ! [ -e $1 ]; then echo "$0 file string|less -S # greps in chunks"; exit; fi

FILE="$1"
MATCH="$2"

nlines=$(wc -l < $1)
chunk=1000
LC_ALL=C
for((i=1; i < nlines; i += chunk))
do
  sed -n $i,+$((chunk - 1))p $1 | grep -F -a -z -C 500 $2
done