.\" Copyright (c) 1988 The Regents of the University of California.
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.\"	@(#)su.1	6.6 (Berkeley) 09/26/88
.\"
.TH SU 1 ""
.UC
.SH NAME
su \- substitute user id
.SH SYNOPSIS
.B su
[-flm] [login]
.SH DESCRIPTION
\fISu\fP requests the password for \fIlogin\fP (or for ``root'', if no
login is provided), and switches to that user and group ID.  A shell is
then invoked.
.PP
By default, your environment is unmodified with the exception of
\fIUSER\fP, \fIHOME\fP, and \fISHELL\fP.  \fIHOME\fP and \fISHELL\fP
are set to the target login's \fI/etc/passwd\fP values.  \fIUSER\fP
is set to the target login, unless the target login has a UID of 0,
in which  case it is unmodified.  The invoked shell is the target
login's.  This is the traditional behavior of \fIsu\fP.
.PP
The \fI-l\fP option simulates a full login.  The environment is discarded
except for \fIHOME\fP, \fISHELL\fP, \fIPATH\fP, \fITERM\fP, and \fIUSER\fP.
\fIHOME\fP and \fISHELL\fP are modified as above.  \fIUSER\fP is set to
the target login.  \fIPATH\fP is set to ``/usr/ucb:/bin:/usr/bin''.
\fITERM\fP is imported from your current environment.  The invoked shell
is the target login's, and \fIsu\fP will change directory to the target
login's home directory.
.PP
The \fI-m\fP option causes the environment to remain unmodified, and
the invoked shell to be your login shell.  No directory changes are
made.  As a security precaution, if the target shell is not a standard
shell (as defined by \fIgetusershell\fP(3)) it is invoked instead of
your login shell.
.PP
If the invoked shell is \fIcsh\fP, the \fI-f\fP option prevents it from
reading the \fI.cshrc\fP file.  Otherwise, this option is ignored.
.PP
Only users in group 0 (normally ``wheel'') can \fIsu\fP to ``root''.
.PP
By default (unless the prompt is reset by a startup file) the super-user
prompt is set to ``#'' to remind one of its awesome power.
.SH "SEE ALSO"
csh(1), login(1), sh(1), passwd(5), group(5), environ(7)