The exit code, or error level, of all MAF utilities is 0 if successful. Various exit codes are used if the program fails to complete successfully:
Exit code 1 is used if there is a usage error, or the input supplied to the program is invalid in some way. In this case the program aborts with an error message sent to stderr, without producing its normal output.
Some programs can also exit with exit code 2, which means that they have been aborted with provisional or incomplete results. This applies notably to automata, and to two programs provided for KBMAG compatibility: kbprog and kbprogcos.
Exit code 3 means that the program has failed because of an I/O error. This error would normally be caused by a required file's unexpected non existence, or inaccessibility, or by the program running out of disk space.