Tests if an app is installed. Response code could be checked by an if-test

isappinstalled

#!/bin/bash

#Ensure we have one argument specified on the CLI
if [ -z "$1" ]; then ARG_ERR=ERR; fi
if [ -n "$ARG_ERR" ];
then
    echo "Checks if an app (passed as a parameter) is installed/reachable"
    echo " on this machine by using the 'hash' command."
    echo "Usage: isappinstalled <appname>"
    echo "Returns: 0 if is installed, 1 if not installed."
    exit
fi


hash $1 2>&- || { echo >&2 "I require $1 but it's not installed."; exit 1; }