#!/bin/bash

# Given a filename, a regex pattern to match and a replacement string:
# Replace string if found, else no change.
# (# $1 = filename, $2 = pattern to match, $3 = replacement)
               
grep $2 $1 >/dev/null
if [ $? -eq 0 ]; then
	# Pattern found; replace in file
	sed -i "s/$2/$3/g" $1 >/dev/null
fi