Are there any standard exit status codes in Linux?

Question

A process is considered to have completed correctly in Linux if its exit status was 0.

I\'ve seen that segmentation faults often result in an exit status of 11, thou

Answer 1

To a first approximation, 0 is sucess, non-zero is failure, with 1 being general failure, and anything larger than one being a specific failure. Aside from the trivial exceptions of false and test, which are both designed to give 1 for sucess, there's a few other exceptions I found.

More realistically, 0 means sucess or maybe failure, 1 means general failure or maybe sucess, 2 means general failure if 1 and 0 are both used for sucess, but maybe sucess as well.

The diff command gives 0 if files compared are identical, 1 if they differ, and 2 if binaries are different. 2 also means failure. The less command gives 1 for failure unless you fail to supply an argument, in which case, it exits 0 despite failing.

The more command and the spell command give 1 for failure, unless the failure is a result of permission denied, nonexistent file, or attempt to read a directory. In any of these cases, they exit 0 despite failing.

Then the expr command gives 1 for sucess unless the output is the empty string or zero, in which case, 0 is sucess. 2 and 3 are failure.

Then there's cases where success or failure is ambiguous. When grep fails to find a pattern, it exits 1, but it exits 2 for a genuine failure (like permission denied). Klist also exits 1 when it fails to find a ticket, although this isn't really any more of a failure than when grep doesn't find a pattern, or when you ls an empty directory.

So, unfortunately, the unix powers that be don't seem to enforce any logical set of rules, even on very commonly used executables.