.TH SU 1 11/16/79
.UC
.SH NAME
su \- substitute user id temporarily
.SH SYNOPSIS
.B su
[ userid ]
.SH DESCRIPTION
.I Su
demands the password of the specified
.I userid,
and if it is given,
changes to that 
.I userid
and invokes the Shell
.IR sh (1)
without changing the current directory.
The user environment
is unchanged except for HOME and SHELL,
which are taken from the password file
for the user being substituted
(see
.IR environ (5)).
The new user ID stays in force until the Shell exits.
.PP
If no 
.I userid
is specified, `root' is assumed.
To remind the super-user of his responsibilities,
the Shell substitutes `#' for its usual prompt.
.SH "SEE ALSO"
sh(1)
.SH BUGS
Local administrative rules cause restrictions to
be placed on who can
.I su
to `root', even with the root password.
These rules vary from site to site.