Function to make an ssh tunnel that forwards a local display port back to the login node's display port in an LSF cluster that doesn't support X Forwarding

tund.sh

# Tunnel Display
# This function sets up an ssh tunnel that forwards a local display port
# back to the login node's display port. The tunnel is controlled by the
# socket in $HOME/tmp/ssh-${LSB_SUB_HOST}-${HOSTNAME}-${DISPLAY_NUMBER}.
# The ssh tunnel is in the background and keeps running even after the
# interactive shell is closed, thus preventing completion of the LSF job.
# To avoid this, we setup a trap on SIGINT SIGTERM EXIT that uses the ssh
# control socket to signal the tunnel to exit.
tund(){
if [[ -n $LSB_JOBID ]]; then
        DISPLAY_NUMBER=$(echo $DISPLAY | sed 's/.\+:\([0-9]\+\)\.[0-9]\+/\1/')
        COOKIE=$(xauth list | grep $LSB_SUB_HOST/unix:$DISPLAY_NUMBER | awk '{print $2,$3}')
        xauth add $HOSTNAME/unix:$DISPLAY_NUMBER $COOKIE
        SSH_CTRL_SOCKET="$HOME/tmp/ssh-${LSB_SUB_HOST}-${HOSTNAME}-${DISPLAY_NUMBER}"
        if [[ -f $SSH_CTRL_SOCKET ]]; then
                echo "Error: $SSH_CTRL_SOCKET SSH control socket already exists"
                return 1
        fi
        ssh -M -S $SSH_CTRL_SOCKET -f -N -L60${DISPLAY_NUMBER}:127.0.0.1:60${DISPLAY_NUMBER} $LSB_SUB_HOST
        export DISPLAY=localhost:$DISPLAY_NUMBER
        export SSH_CTRL_SOCKET
        trap "if [[ -n "$SSH_CTRL_SOCKET" ]] && [[ -S "$SSH_CTRL_SOCKET" ]]; then ssh -S $SSH_CTRL_SOCKET -O exit $LSB_SUB_HOST; fi" SIGINT SIGTERM EXIT
else
        echo "Not on a compute node"
        return 1
fi
}
export -f tund