Handling command line options in bash scripts, example

cmdline-example.sh

# Starts the elasticsearch node container, optionally setting
# a cluster name and host IP to expose to other nodes. Mounts
# the directory at /var/lib/elasticsearch to the same location
# on the host.
#
# exposes ports:
#    9200 = elasticsearch http
#    9300 = elasticsearch transport
#
IP=""
C_NAME=""

print_help() {
    echo "Usage: start-container [-h 'IP_ADDRESS'] [-c CLUSTER_NAME]"
    echo "Options:"
    echo "    -i|--hostip      : host IP to expose to other es nodes"
    echo "    -c|--cluster     : name of the cluster to join"
    echo "    -h|--help        : print this help screen"
}

while [[ $# > 0 ]]
do
    key="$1"

    case $key in
        -i|--hostip)
        IP="$2"
        shift
        ;;
        -c|--cluster)
        C_NAME="$2"
        shift
        ;;
        -h|--help)
        print_help
        exit 0
        ;;
        *)
        echo "Unknown option $key"
        print_help
        exit 1
        ;;
    esac
    shift
done

sudo docker run -i -t\
 -e "CLUSTER_NAME=$C_NAME"\
 -e "HOST_IP=$IP"\
 -v /var/lib/elasticsearch:/var/lib/elasticsearch\
 --name="elasticsearch" -h="es" -p 9200:9200 -p 9300:9300 feedgrub/elasticsearch