Exit codes and error handling
How $?, PIPESTATUS, set -e, and pipefail combine to tell a script what actually succeeded or failed, and where each one falls short.
scripting
Shell scripting techniques
Your first script
Write, mark executable, and run your first bash script, plus what the shebang line and PATH lookup actually do.
Variables and quoting
Why unquoted variables break bash scripts, when to use double vs single quotes, and how glob characters make it worse.
Conditionals and test
The difference between [ and [[ in bash, why unquoted variables crash [ but not [[, and pattern matching with case.
Bulk rename a batch of files
Rename many files at once with a plain bash loop, safely handling spaces and previewing changes before committing.