die() {
    # Use notify-send to send errors when not in a terminal
    # [ -t 0 ] only works outside of pipes
    [ -t 0 ] || notify-send "$@" && >&2 echo "$@"
    exit 1
}

# Output error to stderr and to graphical notification
notify_err() {
    tee /dev/fd/2 | xargs -r -n1 -d "\n" notify-send
}

assert_exists() {
    for c in $@; do
        which "$c" > /dev/null 2>&1 || die "$c doesn't appear to be installed"
    done
}

check_exists() {
    for c in $@; do
        which "$c" > /dev/null 2>&1 || return 1
    done
}