4.2BSD/usr/man/man1/login.1

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.TH LOGIN 1 "1 April 1981"
.UC 4
.SH NAME
login \- sign on
.SH SYNOPSIS
.B login
[ username ]
.SH DESCRIPTION
The
.I login
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 \*(lqHow to Get Started\*(rq for how to dial up initially.
.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,
and
the message of the day is printed,
as is the time he last logged in (unless 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  sh (1))
according to specifications found in a password file.
Argument 0 of the command interpreter is \*(lq\-sh\*(rq, or
more generally the name of the command interpreter with
a leading dash (\*(lq\-\*(rq) prepended.
.PP
Login also initializes the
environment
.IR environ (7)
with information specifying home directory, command interpreter, terminal
type (if available) and user name.
.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).
.SH FILES
.ta \w'/usr/spool/mail/*\ \ 'u
/etc/utmp	accounting
.br
/usr/adm/wtmp	accounting
.br
/usr/spool/mail/*	mail
.br
/etc/motd	message-of-the-day
.br
/etc/passwd	password file
.br
/etc/nologin	stops logins
.br
\&.hushlogin	makes login quieter
.br
/etc/securetty	lists ttys that root may log in on
.SH "SEE ALSO"
init(8), getty(8), mail(1), passwd(1), passwd(5), environ(7),
shutdown(8)
.SH DIAGNOSTICS
\*(lqLogin incorrect,\*(rq
if the name or the password is bad.
.br
\*(lqNo Shell\*(rq, \*(lqcannot open password file\*(rq,
\*(lqno directory\*(rq:
consult a programming counselor.
.SH BUGS
An undocumented option,
.B \-r
is used by the remote login server,
.IR rlogind (8C)
to force
.I login
to enter into an initial connection protocol.