login
[options
]
Sign on and identify yourself to the system. At the beginning of each terminal session, the system prompts you for your username and, if relevant, a password. The options are usually not used.
user
Sign on as user
(instead of being prompted).
tty
Specify the pathname of the tty
that serves as the login port.
var
=value
When specified after the username,
assign a value
to one or more environment variables.
PATH and SHELL can't be changed.)