exit statement is used with a value
(see Exit Statement), then gawk exits with
the numeric value given to it.
Otherwise, if there were no problems during execution,
gawk exits with the value of the C constant
EXIT_SUCCESS. This is usually zero.
If an error occurs, gawk exits with the value of
the C constant
EXIT_FAILURE. This is usually one.
If gawk exits because of a fatal error, the exit
status is 2. On non-POSIX systems, this value may be mapped