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.\"	from: @(#)su.1	8.2 (Berkeley) 4/18/94
.\"	$NetBSD: su.1,v 1.14 1997/10/19 23:31:52 lukem Exp $
.\"
.Dd April 18, 1994
.Dt SU 1
.Os
.Sh NAME
.Nm su
.Nd substitute user identity
.Sh SYNOPSIS
.Nm
.Op Fl flm
.Op Ar login 
.Op Ar -c shell arguments
.Sh DESCRIPTION
.Nm
requests the password for
.Ar login
and switches to
that user and group ID after obtaining proper authentication.
A shell is then executed, and any additional
.Ar "shell arguments"
after the login name
are passed to the shell.
If
.Nm
is executed by root, no password is requested and a shell
with the appropriate user ID is executed.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl c
Invoke the following command in a subshell as the specified user.
.It Fl f
If the invoked shell is
.Xr csh 1 ,
this option prevents it from reading the
.Dq Pa .cshrc
file.
.It Fl l
Simulate a full login.
The environment is discarded except for
.Ev HOME ,
.Ev SHELL ,
.Ev PATH ,
.Ev TERM ,
and
.Ev USER .
.Ev HOME
and
.Ev SHELL
are modified as above.
.Ev USER
is set to the target login.
.Ev PATH
is set to
.Dq Pa /bin:/usr/bin .
.Ev TERM
is imported from your current environment.
The invoked shell is the target login's, and
.Nm
will change directory to the target login's home directory.
This option is identical to just passing "-", as in "su -".
.It Fl m
Leave the environment unmodified.
The invoked shell is your login shell, and no directory changes are made.
As a security precaution, if the target user's shell is a non-standard
shell (as defined by
.Xr getusershell 3 )
and the caller's real uid is
non-zero,
.Nm
will fail.
.El
.Pp
The
.Fl l
and
.Fl m
options are mutually exclusive; the last one specified
overrides any previous ones.
.Pp
Only users in group
.Dq wheel
(normally gid 0)
or group
.Dq admin
(normally gid 20) can
.Nm
to
.Dq root .
.Pp
By default (unless the prompt is reset by a startup file) the super-user
prompt is set to
.Dq Sy \&#
to remind one of its awesome power.
.Sh SEE ALSO
.Xr csh 1 ,
.Xr login 1 ,
.Xr sh 1 ,
.Xr skey 1 ,
.Xr kinit 1 ,
.Xr kerberos 1 ,
.Xr passwd 5 ,
.Xr group 5 ,
.Xr environ 7
.Sh ENVIRONMENT
Environment variables used by
.Nm 
:
.Bl -tag -width "HOME"
.It Ev HOME
Default home directory of real user ID unless modified as
specified above.
.It Ev PATH
Default search path of real user ID unless modified as specified above.
.It Ev TERM
Provides terminal type which may be retained for the substituted
user ID.
.It Ev USER
The user ID is always the effective ID (the target user ID) after an
.Nm
unless the user ID is 0 (root).
.El
.Sh HISTORY
A
.Nm
command appeared in
.At v7 .