docker-machine command with default machine name

dm

#!/bin/bash
set -euo pipefail

MACHINE_NAME=$(printf "%q" ${DOCKER_MACHINE_NAME:-null})
if [ "$MACHINE_NAME" == "null" ]; then
    echo "Error: No docker machine env variables are set"
    exit -1;
fi

DM_SPECIAL_COMMANDS=(
    'config' 'env' 'inspect' 'ip' 'kill' 'provision'
    'regenerate-certs' 'restart' 'scp' 'ssh' 'start'
    'status' 'stop' 'upgrade'
)

PRINT_EXPLANATION=0

SCRIPT_NAME=`basename "$0"`
ARGS="$@"
FIRST_ARG="${1:-}"
SECOND_ARG="${2:-}"
LAST_ARG="${@: -1}"

if [ "$LAST_ARG" == "--explain" ]; then
    # remove last arg
    ARGS="${@:1:${#}-1}"
    PRINT_EXPLANATION=1
fi

parse () {

    if [ -z "$ARGS" ]; then
        return
    fi

    # if using a docker-machine flag or an option, it's too complicated to parse
    if [ ${FIRST_ARG:0:1} == '-' ]; then
        # echo "skipped - option usage detected"
        return
    fi

    USING_SPECIAL_COMMAND=0
    for COMMAND in "${DM_SPECIAL_COMMANDS[@]}"; do
        if [ "$COMMAND" == "$FIRST_ARG" ]; then
            USING_SPECIAL_COMMAND=1
            SPECIAL_COMMAND="$COMMAND"
            break
        fi
    done
    
    if [ $USING_SPECIAL_COMMAND == 0 ]; then
        # echo "skipped - not using a special command"
        return
    fi

    # Skip injection if machine name is already used in the original command
    ALL_MACHINE_NAMES=$(docker-machine ls -t 0 --quiet)
    GREP_ARGS=$(echo ${ALL_MACHINE_NAMES} | sed 's/ /\\|/g')
    if [ ! -z "$(echo $ARGS | grep -w $GREP_ARGS)" ]; then
        # echo "skipped - found a machine name in the command"
        return
    fi
    
    ARGS=$(echo $ARGS | sed -e "s/^${SPECIAL_COMMAND}\b/${SPECIAL_COMMAND} $MACHINE_NAME/")

}

parse

if [ "$PRINT_EXPLANATION" == 1 ]; then
    set -x
fi

docker-machine $ARGS

This bash script injects the default docker machine name into commands that are supported by the script.

The default machine name is taken from DOCKER_MACHINE_NAME env variable.
Usage example:

dm ssh

This will run docker-machine ssh $DOCKER_MACHINE_NAME

The supported commands are config, env, inspect, ip, kill, provision, regenerate-certs, restart, scp, ssh, start, status, stop and upgrade

The script will not inject the default machine name if a supported command is not used as the first arguments or if there's a use of an existing machine name in the command.
This means that running dm ssh dev, will run docker-machine ssh dev as usual without the usage of DOCKER_MACHINE_NAME env variable.

You can add --explain as last parameter to print the actual command that the script runs.

To use this script, download the dm file and make it executable by running chmod +x dm