server_control.py

#!/usr/bin/env python3

"""
Usage:
    ./server_control show -e ENVIRONMENT -a APPLICATION
    ./server_control terminate -e ENVIRONMENT -a APPLICATION
    ./server_control launch -e ENVIRONMENT -a APPLICATION

Options:
    -e ENVIRONMENT  Environment the server is in. Supported values are staging, production.
    -a APPLICATION  Application name. 

Commands:
    show        Show instance metadata.
    terminate   Shut down the instances.
    launch      Create a new instance with the given tags.
"""

import sys
try:
    from docopt import docopt
except ModuleNotFoundError:
    print("\n".join(["You don't have docopt installed. Install it with the command:",
        "\tpip install docopt"]), file=sys.stderr)
    sys.exit(10)

def parse_args(argv):
    args = {}
    docopted_args = docopt(__doc__, argv=argv[1:])
    print(docopted_args)

    for command in ["show", "terminate", "launch"]:
        if docopted_args[command]:
            args["command"] = command
            break

    accepted_environments = ["staging", "production"]
    if docopted_args["-e"] not in accepted_environments:
        print("Unrecognized environment '{}'. Supported environments are {}\n{}".format(docopted_args["-e"], 
            ", ".join(accepted_environments), __doc__))
        sys.exit(11)

    args["environment"] = docopted_args["-e"]
    args["application"] = docopted_args["-a"]

    return args

def main():
    args = parse_args(sys.argv)

    print("Running command '{command}' in environment '{environment}' for application '{application}'".format(**args)

if __name__ == '__main__':
    main()

server_control.sh

#!/bin/bash
set -e

## Set a usage message
USAGE=$(cat <<EOF

    Usage:
        ./server_control show -e ENVIRONMENT -a APPLICATION
        ./server_control terminate -e ENVIRONMENT -a APPLICATION
        ./server_control launch -e ENVIRONMENT -a APPLICATION

    Options:
        -e ENVIRONMENT  Environment the server is in. Supported values are staging, production.
        -a APPLICATION  Application name. 

    Commands:
        show        Show instance metadata.
        terminate   Shut down the instances.
        launch      Create a new instance with the given tags.

EOF
)

## Exit quickly if there's not the right number of argments.
if [[ $# -ne 5 ]]; then
    ( >&2 echo "Need exactly 5 arguments. $USAGE")
    exit 1
fi

## Pop the positional argument off.
case "$1" in
    show|terminate|launch ) 
        COMMAND=$1
        shift
        ;;
    * )
        ( >&2 echo "unrecognized command '$1' $USAGE")
        exit 2
        ;;
esac

## Parse the flags
APPLICATION=""
ENVIRONMENT=""
while getopts ":e:a:" opt; do
    case ${opt} in
        e )
            case "$OPTARG" in
                staging|production )
                    ENVIRONMENT=$OPTARG
                    ;;
                * )
                    ( >&2 echo "unsupported value '$OPTARG' $USAGE" )
                    exit 3
            esac
            ;;
        a )
            APPLICATION=$OPTARG
            ;;
        : ) 
            ( >&2 echo "-$OPTARG needs an argument $USAGE")
            exit 4
            ;;
        \? )
            ( >&2 echo "unrecognized option -$opt $USAGE")
            exit 5
            ;;
    esac
done
shift $((OPTIND -1))

## Validate the variables
if [[ -z "$ENVIRONMENT" ]] || [[ -z "$APPLICATION" ]]; then
    ( >&2 echo "need both environment and application specified $USAGE")
    exit 5
fi


echo "Running command '$COMMAND' in '$ENVIRONMENT' for application '$APPLICATION'"