In Bash scripts set -e

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In Bash scripts set -e

Author：JIYIK Last Updated：2025/03/20 Views：

The -h option instructs the shell to exit if the command returns a non-zero exit status set -e. In simple terms, the shell exits if the command fails.

In Debian package management scripts, set -ethis is also known as set -o errexit. According to Debian policy, this option is required in some scripts; the goal seems to be to avoid any unhandled error conditions.

In practice, this means that you must understand the situations in which the commands you run might return errors and address each problem explicitly.

Use outside of a Bash function`set -e`

Let's write a Bash script to use hello_worldthe print function Hello World. We will use it outside of the function set -e.

set -eOnly used to write or set error display codes.

#!/bin/bash
set -e
function hello_world()
{
echo "Hello World!"
}
hello_world

Output:

Hello World!

Use in Bash function bodies`set -e`

Now, we will set -eplace the inside a function in the above script.

#!/bin/bash
function hello_world()
{
set -e
echo "Hello World!"
}
hello_world

Output:

Hello World!

Using it inside or outside a function set-ewill not affect our output.

`set -e`and`trap`

set -eThe command instructs the terminal to throw an exception when an error is detected, causing the code to stop executing. trapThe keyword allows you to use a built-in function ERRthat accepts the error line number and passes it to the error function.

Let’s look at an example.

#!/bin/bash
set -e
function error()
{
echo "error at $1"
}
trap 'error $LINENO' ERR

errors

We create a function errorand use a shell variable $1to store the line number where the error occurred.

Output:

demo.sh: line 9: errors: command not found
error at 9

demo.shis the name of the script file that contains the above script.

If one line of a script fails, but the last line succeeds, the entire script is considered successful. Therefore, it is easy to ignore errors.

Error tolerance is much better in scripts, and set -eprovides that for you.

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