For completeness I will note that Windows is completely different. The plain exit status (1 for typical command failures) appears in the os.system result rather than a wait-encoded value. And, incidentally, an MSVC program which calls abort() will return an exit status of 3. A process that terminates another process with TerminateProcess can set that process's exit status to an arbitrary 32-bit value. The MSVC exit function limits the value to one byte, but the raw ExitProcess system call supports any 32-bit value.
And, just for fun, two versions of "cat" on my system (one supplied with Git, and one from gnuwin32) return 0x10200 and 0xC000013A respectively when terminated by Ctrl-C. I think the first is some effort at an alternate encoding that's compatible with plain exit statuses in the low-order byte, and the second is the value of STATUS_CONTROL_C_EXIT (an HRESULT). I found some information on google suggesting that some unix-alike layers use an exit status of 0xC00002NN to represent signals (with, once again, plain exit status being a value of 0x00NN). All of these values are available as the returned value from os.system. -- https://mail.python.org/mailman/listinfo/python-list
