Once applying for a job I took a test for Linux knowledge.

I remember one question I didn't gave a correct answer for: "Where is the location of 'mtab' file?"

OK, that's a dumb question and really it could be better if it were something like "How to get the list of currently mounted file systems?"

And the answer might be "run 'mount' command without arguments". (Please note that 'mount' is shorter than 'cat /etc/mtab' and can be run as unprivileged user).

That is exactly what I've been doing until once I restarted my system into run level 1 (single) mode. File system has to be checked and it have been mounted read-only. I tried to edit something and realized that root file system is not writable despite 'mount' says it's been mounted RW. (Without arguments 'mount' command just prints '/etc/mtab' to console)

So the only way to get reliable list of currently mounted file systems would be to print '/proc/mounts' file content.