What is set -e in bash?

You’ll often see this at the start of a bash script:

set -e

This instructs the script to exit if any command it executes exits with a non-zero status code.

For example, in the below script:

#!/bin/bash
set -e

echo "This is a test script."

# This command will fail because the directory does not exist
cd /nonexistent/directory

# This command will not be executed because the script will exit after the cd command fails
echo "You will not see this message."

You’ll see the "This is a test script." in the console but you won’t see "You will not see this message" because the cd /nonexistent/directory command will fail with a non-zero status code. The set -e causes the script to exit as soon as it encounters a non-zero status code.

If you omit set -e from the start of the script, you will see the second message.