Bash script for controlling VNC sessions

vnc.sh

#!/usr/bin/env bash

display_help() {
    echo "Usage: `basename "$0"` OPTIONS ACTION

Options must be specified before any action, and only one action may be specified.

Options:

    -g | --geometry size    specify VNC session display size
    -s | --server name      specify VNC server name in case it's not the current host
    -h | --help             display this message and exit

Actions:

    list                    list open sessions
    create                  create session
    kill session            kill session

Environment variables:

    VNC_GEOMETRY            VNC session display size
    VNC_SERVER              VNC server name"
}

list_sessions() {
    server=$1

    if [ -z "$server" ]; then
        if ! sessions=`ls ~/.vnc/*.pid 2>&1`; then
            echo 'Error: no open VNC sessions on current host'
            exit 1
        fi
    else
        if ! sessions=`ssh -q "$server" 'ls ~/.vnc/*.pid' 2>&1`; then
            echo "Error: no open VNC sessions on current $server"
            exit 1
        fi
    fi

    for session in $sessions; do
        basename -s .pid "$session"
    done
}

create_session() {
    server=$1
    geometry=$2

    if [ -z "$server" ]; then
        if ! vncserver -geometry "$geometry" > /dev/null; then
            echo "Error: couldn't create VNC session on current host"
            exit 1
        fi
    else
        if ! ssh -q "$server" "vncserver -geometry $geometry" > /dev/null; then
            echo "Error: couldn't create VNC session on $server"
            exit 1
        fi
    fi

    list_sessions "$server"
}

kill_session() {
    server=$1
    session=$2

    if [ -z "$session" ]; then
        echo 'Error: must specify VNC session to terminate'
        exit 1
    fi

    if [ -z "$server" ]; then
        if ! vncserver -kill "$session" > /dev/null; then
            echo "Error: couldn't kill VNC session $session on current host"
            exit 1
        fi
    else
        if ! ssh -q "$server" "vncserver -kill $session" > /dev/null; then
            echo "Error: couldn't kill VNC session $session on $server"
            exit 1
        fi
    fi
}

if [ $# -eq 0 ]; then
    echo 'Error: no arguments specified'
    display_help
    exit 1
fi

if [ -n "$VNC_GEOMETRY" ]; then
    geometry=$VNC_GEOMETRY
else
    geometry=1024x768
fi

server=$VNC_SERVER

while [ $# -gt 0 ]; do
    case "$1" in
        -g | --geometry)
            geometry=$2
            shift
            shift
            ;;
        -s | --server)
            server=$2
            shift
            shift
            ;;
        -h | --help)
            display_help
            exit 0
            ;;
        list)
            list_sessions "$server"
            exit 0
            ;;
        create)
            create_session "$server" "$geometry"
            exit 0
            ;;
        kill)
            kill_session "$server" "$2"
            exit 0
            ;;
        -*)
            echo "Error: unrecognized option $1"
            display_help
            exit 1
            ;;
        *)
            echo "Error: extra argument $1"
            display_help
            exit 1
            ;;
    esac
done