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.\" Copyright 1989 - 1990, Julianne Frances Haugh
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
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.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of Julianne F. Haugh nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY JULIE HAUGH AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL JULIE HAUGH OR CONTRIBUTORS BE LIABLE
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\"
.\" $Id: su.1,v 1.6 2000/08/26 18:27:17 marekm Exp $
.\"
.TH SU 1
.SH NAME
su \- Change user ID or become super-user
.SH SYNOPSIS
.BR su " [" - ]
.RI [ username " [" args ]]
.SH DESCRIPTION
.B su
is used to become another user during a login session.
Invoked without a username, \fBsu\fR defaults to becoming
the super user.
The optional argument \fB\-\fR may be used to provide an
environment similiar to what the user would expect had
the user logged in directly.
.PP
Additional arguments may be provided after the username,
in which case they are supplied to the user\'s login shell.
In particular, an argument of \fB-c\fR will cause the
next argument to be treated as a command by most command
interpreters.
.\" The command will be executed under the shell specified by
.\" \fB$SHELL\fR, or if undefined, by the one specified in
.\" \fI/etc/passwd\fR.
.\" XXX - the above was not quite correct. --marekm
The command will be executed by the shell specified in
\fI/etc/passwd\fR for the target user.
.PP
The user will be prompted for a password, if appropriate.
Invalid passwords will produce an error message.
All attempts, both valid and invalid, are logged to detect
abuses of the system.
.PP
The current environment is passed to the new shell. The value of
\fB$PATH\fR is reset to \fB/bin:/usr/bin\fR for normal users, or
\fB/sbin:/bin:/usr/sbin:/usr/bin\fR for the super user. This may be
changed with the \fBENV_PATH\fR and \fBENV_SUPATH\fR definitions in
\fI/etc/login.defs\fR.
.PP
A subsystem login is indicated by the presense of a "*" as the first
character of the login shell. The given home directory will be used as
the root of a new filesystem which the user is actually logged into.
.SH CAVEATS
.PP
This version of \fBsu\fR has many compilation options, only some of which
may be in use at any particular site.
.SH Files
/etc/passwd \- user account information
.br
/etc/shadow \- encrypted passwords and age information
.br
$HOME/.profile \- initialization script for default shell
.SH SEE ALSO
.BR login (1),
.BR sh (1),
.BR suauth (5),
.BR login.defs (5)
.SH AUTHOR
Julianne Frances Haugh (jfh@austin.ibm.com)