2.11BSD/man/cat1/login.0
LOGIN(1) UNIX Programmer's Manual LOGIN(1)
NAME
login - sign on
SYNOPSIS
login [ -p ] [ username ]
DESCRIPTION
The _l_o_g_i_n command is used when a user initially signs on, or
it may be used at any time to change from one user to
another. The latter case is the one summarized above and
described here. See "How to Get Started" for how to dial up
initially.
If _l_o_g_i_n 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.
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 ".hushlogin" file in his
home directory; this is mostly used to make life easier for
non-human users, such as _u_u_c_p.
_L_o_g_i_n initializes the user and group IDs and the working
directory, then executes a command interpreter (usually
_c_s_h(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 ("-").
Login also modifies the environment _e_n_v_i_r_o_n(7) with informa-
tion specifying home directory, command interpreter, termi-
nal type (if available) and user name. The `-p' argument
causes the remainder of the environment to be preserved,
otherwise any previous environment is discarded.
If the file /etc/nologin exists, _l_o_g_i_n prints its contents
on the user's terminal and exits. This is used by _s_h_u_t_-
_d_o_w_n(8) to stop users logging in when the system is about to
go down.
Login is recognized by _s_h(1) and _c_s_h(1) and executed
directly (without forking).
FILES
/var/run/utmp accounting
/usr/adm/wtmp accounting
/usr/spool/mail/* mail
/etc/motd message-of-the-day
/etc/passwd password file
/etc/nologin stops logins
Printed 11/26/99 November 27, 1996 1
LOGIN(1) UNIX Programmer's Manual LOGIN(1)
.hushlogin makes login quieter
SEE ALSO
init(8), getty(8), mail(1), passwd(1), passwd(5),
environ(7), shutdown(8), rlogin(1c)
DIAGNOSTICS
"Login incorrect," if the name or the password is bad.
"No Shell", "cannot open password file", "no directory":
consult a programming counselor.
BUGS
An undocumented option, -r is used by the remote login
server, _r_l_o_g_i_n_d(8C) to force _l_o_g_i_n to enter into an initial
connection protocol. -h is used by _t_e_l_n_e_t_d(8C) and other
servers to list the host from which the connection was
received.
Printed 11/26/99 November 27, 1996 2