3 advices to write robust Bash scripts

To write robust Bash scripts, I recommend you to:

1. Activate the Bash options: errexit, nounset

Add these two options at the top of your BASH scripts:

  • errexit will stop your Bash script each time a command in your script returns an exit code different than “0”. It does not show any message when it quits, this is why it is important to show a traceback (check the second advice below “show a Bash traceback”).
  • nounset will stop your script and output an error if you attempt to use undefined variables. nounset is very important because it can avoid you to run dangerous commands like: rm –fr “/$undefinedvariable”

2. Show a Bash Traceback

Because the option “errexit” does not show any message when it stops your Bash script, I recommend you to add the code below to show a traceback each time “errexit” forces your Bash script to stop:

The traceback will help you to know exactly which command in your Bash script exited with an error code different than “0”:

3. Check your Bash scripts with shellcheck and follow the recommendations of Advanced Bash-Scripting Guide.

Temporarily prevent Linux from shutting down

Accidental shutdown or reboot is a serious blunder, especially if the kernel is being updated in the background.

In order to prevent Linux from shutting down while your update script is running, I recommend you to use systemd-inhibit:

systemd-inhibit will block the shutdown or reboot until the update script is finished.

Additional options:

  • –who=”your name”
    A human-readable name
  • list
    List all active inhibition locks

How to stop and remove all docker images and containers

Docker is a great tool, but sometimes it can consume a lot of disk space. docker-clean is a simple bash script you can use to remove all docker images and containers with one command:

To stop and remove all Docker containers:

To remove all Docker images: