logname prints the calling user's name, as found in a system-maintained file (often /var/run/utmp or /etc/utmp), and exits with a status of 0. If there is no entry for the calling process, logname prints an error message and exits with a status of 1.
The only options are --help and --version. See Common options.
An exit status of zero indicates success, and a nonzero value indicates failure.