Question

Sample script is shown below:

#!/bin/bash
sed -i~ 's/user1/user2/g' myfile.txt

It replaces user1 with user2 in myfile.txt

How can I change above script to get confirmation that the script found user1 & replaced it with user2?

Basically, if it doesn’t find user1, it should give an alert message on the command prompt.

Thanks!

Answer 1

An alternative to diffing after is to grep before:

grep -q 'user1' myfile.txt && sed -i~ 's/user1/user2/g' myfile.txt || echo "user1 not there"

The -q means that grep runs quietly and returns success if found, so then and only then will it go on to do the replacement.