.\" Copyright 1989 - 1994, Julianne Frances Haugh
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.\"	$Id: login.1,v 1.6 1999/06/07 16:40:44 marekm Exp $
.\"
.TH LOGIN 1
.SH NAME
login \- Begin session on the system
.SH SYNOPSIS
.B login
.RI [ username " [" environmental-variables ]]
.\" XXX - document -f -h -p -r options
.SH DESCRIPTION
.B login
is used to establish a new session with the system.
It is normally invoked automatically by responding to the
.I login:
prompt on the user\'s terminal.
.B login
may be special to the shell and may not be invoked as a sub-process.
Typically,
.B login
is treated by the shell as \fBexec login\fR which causes the user
to exit from the current shell.
Attempting to execute \fBlogin\fR from any shell but the login shell
will produce an error message.
.PP
When invoked from the \fIlogin:\fR prompt, the user may enter
environmental variables after the username.
These variables are entered in the form \fBNAME=VALUE\fR.
Not all variables may be set in the fashion, notably \fBPATH\fR,
\fBHOME\fR and \fBSHELL\fR.
Additionally, \fBIFS\fR may be inhibited if the user\'s login
shell is \fB/bin/sh\fR.
.PP
The user is then prompted for a password, where appropriate.
Echoing is disabled to prevent revealing the password.
Only a small number of password failures are permitted before
\fBlogin\fR exits and the communications link is severed.
.PP
If password aging has been enabled for your account, you may be
prompted for a new password before proceeding.
You will be forced to provide your old password and the new
password before continuing.
Please refer to \fBpasswd \fR(1) for more information.
.PP
After a successful login,
you will be informed of any system messages and the presence
of mail.
You may turn off the printing of the system message file,
\fI/etc/motd\fR, by creating a zero-length file \fI.hushlogin\fR
in your login directory.
The mail message will be one of "\fBYou have new mail.\fR",
"\fBYou have mail.\fR", or "\fBNo Mail.\fR" according to
the condition of your mailbox.
.PP
Your user and group ID will be set according to their values in
the \fI/etc/passwd\fR file.
The value for \fB$HOME\fR, \fB$SHELL\fR, \fB$PATH\fR, \fB$LOGNAME\fR,
and \fB$MAIL\fR are set according to the appropriate fields in the
password entry.
Ulimit, umask and nice values may also be set according to
entries in the GECOS field.
.PP
On some installations, the environmental variable \fB$TERM\fR will be
initialize to the terminal type on your tty line, as specified in
\fI/etc/ttytype\fR.
.PP
An initialization script for your command interpreter may also be
executed.
Please see the appropriate manual section for more information on
this function.
.SH CAVEATS
.PP
This version of \fBlogin\fR has many compilation options, only some of which
may be in use at any particular site.
.PP
The location of files is subject to differences in system configuration.
.SH FILES
/etc/utmp \- list of current login sessions
.br
/etc/wtmp \- list of previous login sessions
.br
/etc/passwd \- user account information
.br
/etc/shadow \- encrypted passwords and age information
.br
/etc/motd \- system message file
.br
/etc/nologin \- prevent non-root users from logging in
.br
/etc/ttytype \- list of terminal types
.br
$HOME/.profile \- initialization script for default shell
.br
$HOME/.hushlogin \- suppress printing of system messages
.br
.SH SEE ALSO
.PP
.BR getty (8),
.BR mail (1),
.BR passwd (1),
.BR sh (1),
.BR su (1),
.BR login.defs (5),
.\" .BR d_passwd (5),
.BR passwd (5),
.BR nologin (5)
.SH AUTHOR
Julianne Frances Haugh (jfh@bga.com)