Writing Bash scripts

A Bash script is a shell script: a text file of commands the shell runs from top to bottom. It starts with a #!/usr/bin/env bash line and is made runnable with chmod +x. Learn variables, quoting, if tests, for loops, functions, exit codes (a number saying whether a command worked) and script arguments.

Start every script with set -euo pipefail. It stops the script at the first failed command, at an unset variable, or when any command inside a pipe fails. Quote your variables ("$file", not $file) so file names with spaces do not break things.

Run ShellCheck on everything you write; it catches common mistakes. Scripts automate backups, health checks and deploy steps. The same shell lines later end up inside CI pipelines and Dockerfiles.