PWB1/usr/man/man8/setuid.8

.th SETUID VIII 5/31/77
.sh NAME
setuid \*- set user id of command
.sh SYNOPSIS
.bd /etc/setuid
username [ login-directory ]
.br
.it "command     . . ."
.sh DESCRIPTION
.it Setuid
sets the real and effective user ID of the command that follows to
it's argument.
It also changes the login
.it name
and,  optionally, the
login
.it directory.
The line following the setuid command is executed by the shell.
The user ID then reverts to `root' (the only one who can use this
command, after all).