Gcal produces the following exit codes:
Request for help screen, software license or program version (adjustable).
Invalid command line argument / option.
Year out of range for computing the Easter Sunday’s date.
Virtual memory exhausted.
Invalid date part in resource file or in include file.
Invalid month field entry in resource file or in include file.
Invalid day field entry in resource file or in include file.
Malformed #include statement in resource file or in include file.
Illegal recursive/cyclic #include statement in resource file or in include file.
Resource file or include file not found.
Invalid n’th weekday field (only
Missing whitespace separator character between date part and text part.
Response file respectively shell script cannot be written.
Invalid date variable operation.
Referenced date variable undefined.
Invalid date value assigned to date variable.
Sending output to eMail address failed.
Internal error, C function pipe(), fork(), exec*() or unlink() failed.
Error reading resource, include respectively response file.
Illegal character found in response file.
Internal error, invalid value for the size of an internal table occurred.
Invalid date format text specified.
Invalid text variable definition.
Invalid regular expression search pattern specified.
Program aborted by signal.
Exit code not equal zero returned by external command.
Activated -c|C, -f|F name[+…] or -# line option caused no output of resource file entries.
Normal program termination.