Ofc. unset (empty) variables "rm -rf ${variable}/" ... I guess paths are given without a slash at the end (also for that reason).
But also other commands: "hostname", if you type "hostname help" then your new hostname is set to "help". For us that means a full rebuild/reinstallation of the machine is necessary.
This surely has been discussed before, but why not (again): Let me know of your horror stories, if you like.
What a fun day that was....
Then using the killall command on a Solaris box, which just happened to be running the company's Oracle database...
Cue the support line phone ringing off its hook.
Cue BOFH Excuse : "Hmm it appears the server running the database has crashed. We're rebooting it now", etc etc.
Lesson learned : killall on a Sun/Solaris box behaves VERY differently from the killall on Linux :D
There is no trash can in my Unix, deleted is gone forever.
A move (mv) or copy (cp) just overwrites files with the same name (as default)
Right clicking (&executing everything (every line) that just got pasted from the current clipboard/copy-buffer)
Having your shell expand * is just asking for trouble; on most systems you'll have no problems creating more entries in a directory than you can specify arguments on the command line, so rm -rf * will not work from 'somewhere' but rm -rf somewhere should still work fine.
What the hell? Why not just change it back?
Here is another one: I once shut down a server because I wanted to know how to shutdown & reboot. I typed "shutdown -h" (I thought that would display help-pages :)
It was the option to "halt" immediately.
We needed to open a ticket to start the machine up again.
set -o nounset
set -o pipefail
set -o errexit
set -o xtrace
I added them to all my scripts, and I also added all except errexit to ~/.bashrc
The first one would save you from unset variables.
That's what taught me the importance of backups.