#!/bin/bash
# Start up xterm (or any other X command) on the specified host
# Adapted from various versions of xon

prog=`echo $0 | sed 's/^.*\///'`
longhost=`hostname -f 2>/dev/null`
if [ $? -ne 0 ]; then 
    echo $prog: Sorry, $prog only works on Linux/GNU systems. >&2
    exit 1
fi
shorthost=`echo $longhost | sed 's/\..*$//'`

function checkrhosts()
{
    cat <<EOF >&2
$prog: The rsh connection to remote host failed.
$prog: Check the following:
$prog:      - the hostname of the remote machine is correct,
$prog:      - the userid on the remote machine is correct,
$prog:      - the .rhosts file lists `$longhost`,
$prog:      - the permissions on the .rhosts are 0600 (accessible to you only),
$prog:      - the program to be invoked exists on the remote machine.
EOF
}

function usage()
{
    cat <<EOF
Usage: $prog [-user user] [-permit] [-nols] [-debug] [-help] 
             hostname [command...]
EOF
}

function showhelp()
{
    usage
    cat <<EOF

Start an X client on a remote machine. 

   -user user     Set your username on the remote machine
   -permit        Copy the authority cookie to the remote machine
   -nols          Don't make xterm a login shell
   -debug         Show errors
   -help          Display this message
   hostname       The name of the remote machine, eg. hammer.thor.cam.ac.uk
   command...     The command to run on the remote machine (default: xterm -ls)

If your userid on the remote machine is not `id -un`, you must use
-user <userid> to set the userid on the remote machine.

For -permit to work, you must name this machine ($longhost) 
in your .rhosts on the remote machine. You may also need to set the
permissions on the .rhosts using chmod 600 .rhosts.

-nols changes the default command from 'xterm -ls' to 'xterm'.

EOF
    exit 0
}

# Parse the argument list
if [ $# -eq 0 ]; then usage >&2; exit 1; fi
redirect="</dev/null >&0 2>&0 3>&- 4>&- 5>&- 6>&- 7>&- 8>&- &"
ls=-ls; continue=:; permit=no; user=; remotehost=
while $continue; do
    case $1 in
    -user)
	shift
	if [ $# -eq 0 ]; then 
	    echo "$prog: Expected username after -user"
	    exit 1;
	fi
	user="-l $1"; shift ;;
    -debug) shift; redirect= ;;
    -access|-permit) shift; permit=yes ;;
    -ls) shift; ls=-ls ;;
    -nols) shift; ls= ;;
    -help|--help) showhelp ;;
    *)
	if [ -z "$remotehost" ]; then
	    remotehost=$1; shift
	else
	    continue=false 
	fi ;;
    esac
done

# Have compulsory arguments been set?
if [ -z "$remotehost" ]; then
    echo "$prog: You must specify a remote host" >&2
    usage >&2
    exit 1
fi
if [ -z "$DISPLAY" ]; then
    echo "$prog: \$DISPLAY should be set for xcmd to work properly." >&2
    exit 1;
fi

# Is this a local or a remote connection?
remote=yes;
case $DISPLAY in unix:*) DISPLAY=`echo $DISPLAY | sed 's/unix//'` ;; esac
case $DISPLAY in :*) DISPLAY=${longhost}$DISPLAY ;; esac
if [ $remotehost = $shorthost -o $remotehost = $longhost \
    -o $remotehost = localhost ]; then
    remote=no
fi

# Copy the authority across if necessary
rcmd="sh -c"
if [ $remote = yes ]; then
    rcmd="rsh $remotehost $user"
    if [ "$permit" = yes ]; then 
	xauth extract - $DISPLAY | $rcmd \
	PATH=\$PATH:/usr/bin/X11 xauth merge - && \
	echo "$prog: permitted $remotehost access to $DISPLAY"
	if [ $? -ne 0 ]; then
	    checkrhosts;
	    exit 1
	fi
    fi
fi

# Run the command
vars=DISPLAY=$DISPLAY
if [ $# -eq 0 ]; then set - xterm $ls; fi
$rcmd "sh -c '$vars $* $redirect'"
xcmd_exit=$?
if [ "$xcmd_exit" -ne 0 ]; then
    if [ $remote = "yes" ]; then 
	checkrhosts
    else
	echo "$prog: Unable to run $*" >&2
    fi
fi
exit $xcmd_exit