check

#!/bin/bash

NEEDED_COMMANDS="pandoc"
OPTIONAL_COMMANDS="kindlegen"

for cmd in ${NEEDED_COMMANDS} ; do
    if ! command -v ${cmd} &> /dev/null ; then
        echo Please install ${cmd}!
        exit -1
    fi
done

for cmd in ${OPTIONAL_COMMANDS} ; do
    if ! command -v ${cmd} &> /dev/null ; then
        echo You probably want to install ${cmd}!
    fi
done

echo "You're good!"