logname — display
user's login name
The logname utility writes the user's
login name to standard output followed by a newline.
The logname utility explicitly ignores the
LOGNAME and USER environment
variables because the environment cannot be trusted.
The logname utility exits 0 on
success, and >0 if an error occurs.
The logname utility is expected to conform
to IEEE Std 1003.2 (“POSIX.2”).
The logname command appeared in
4.4BSD.