Run the same command on multiple Heroku apps via heroku cli

heroku_multi

#!/bin/bash
#
# A command to run a heroku CLI command for multiple apps
#
# USAGE
#  $ heroku_multi config:set FOO=bar -a app-1 two-app three-apps
#

i=0
position=0
async=0
for arg in "$@"; do
    if [ "$arg" = "-a" ]; then
        position=$i
        let ++position
        let ++position
    fi
    if [ "$arg" = "--async" ]; then
        async=$i
    fi
    let ++i
done

if [ "$async" -gt "0" ]; then
    echo "=====> Executing asynchronously"
fi
if [ "$position" -gt "0" ]; then
    apps=${@:$position}
    let --position
    commands=${@:0:$position}
    for arg in $apps; do
        if [ "$arg" = "--async" ]; then
            continue
        fi
        echo "=====> heroku ${commands} -a ${arg}"
        if [ "$async" -gt "0" ]; then
            heroku "${@:0:$position}" -a $arg &
        else
            heroku "${@:0:$position}" -a $arg
        fi
    done
fi

if [ "$i" -lt "2" ]; then
    echo "Usage: heroku_multi <command> -a app [app] [app...] [--async]"
    echo ""
    echo "      Passing the --async flag will spawn a background shell"
    echo "            for each app command, executing asynchronously"
    echo ""
fi