Avoiding damage.
WHAT SHELL SCRIPTS FREQUENTLY DO
Delete files, change permissions, restart services, and modify configuration.
WHY THAT MATTERS
A fault does real damage, immediately and irreversibly.
WHAT TO ALWAYS DO
Quote every variable Check that variables are set before using them Verify a path before operating on it Use absolute paths, or set the directory explicitly
WHAT THE CLASSIC DISASTER IS
A deletion where a variable was empty, so the path became the root.
WHAT PREVENTS IT
Checking the variable is non-empty before use.
WHAT TO ADD
A dry-run mode, printing what would be done.
WHY
It allows verification before anything is changed.
WHAT TO LOG
What the script did, with timestamps.
WHAT TO HANDLE
Being run twice, so it is safe to repeat.
WHAT TO AVOID
Parsing output of commands whose format may change Assuming commands exist without checking Running as an administrative user unnecessarily
WHAT TO TEST
Every path, including failure paths.
WHAT TO REVIEW
Any script that runs automatically and unattended.
