-.I login
-command
-is used when a user initially
-signs on.
-It may also be used at any time to change
-from one user to another.
-This case is the one summarized first above and described here.
-See \*(lqHow to Get Started\*(rq for how to connect initially.
-The invocation of
-.I login
-for initial sign-on
-is made by a system program or server using the latter form of the command
-and is described below.
-.PP
-If
-.I login
-is invoked without an argument,
-it asks for a user name, and, if
-appropriate, a password.
-Echoing is turned off (if possible) during the typing of the password,
-so it will not appear on the written record of the
-session.
-.PP
-After a successful login,
-accounting files are updated and
-the user is informed of the
-existence of mail.
-The message of the day is printed,
-as is the time of his last login.
-Both are suppressed if he has a \*(lq.hushlogin\*(rq
-file in his home directory; this
-is mostly used to make life easier for non-human users, such as
-.IR uucp .
-.PP
-.I Login
-initializes the user and group IDs and the working directory,
-then executes a command interpreter (usually
-.IR csh (1))
-according to specifications found in a password file.
-Argument 0 of the command interpreter is
-the name of the command interpreter with
-a leading dash (\*(lq\-\*(rq).
-.PP
-Login also modifies the
-environment
-.IR environ (7)
-with information specifying home directory, command interpreter, terminal
-type (if available) and user name.
-The `\-p' argument causes the remainder of the environment to be preserved,
-otherwise any previous environment is discarded.
-.PP
-If the file /etc/nologin exists,
-.I login
-prints its contents on the user's terminal and exits. This is
-used by
-.IR shutdown (8)
-to stop users logging in when the system is about to go down.
-.PP
-Login is recognized by
-.IR sh (1)
-and
-.IR csh (1)
-and executed directly (without forking).
-.PP
-There are several additional options to
-.I login
-for use at initial login.
-With one exception, these options are available only to the superuser.