UNIX for Dummies Questions & Answers

Hello all. I am trying to make a script to edit any file by replacing a string with a string. The script should be able to be applied to any given file. for instance it should be able to replace "foo" with "bar" in the file myFile.txt. I know i need to make a back up file for this to work. I just dont know how to make the sed command for a file that has to be inputted. so far i have

#!/bin/sh
sed s/$1/$2/g ---this is where the input file name should be right??---

My script is called subst1. So i should be able to give the command

./subst1 $1 $2 -file name??-

any words of wisdon would be greatly appreciated.

Code:

#!/bin/bash
old=$1
new=$2
filename=$3
gawk -v o="$old" -v n="$new" '{ gsub(o,n) ;print}' $filename > newfile

Code:

#!/bin/sh
sed "s/$1/$2/g" "$3"

You can then call the script like this:

Code:

./subst1 foo bar file