General Commands Manual
NAME logname — display user's login name
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.
STANDARDS The logname utility conforms to IEEE Std 1003.2-1992 (“POSIX.2”).
HISTORY The logname command appeared in 4.4BSD.