Compare missing commands on new container image

diff.sh

#!/bin/bash

set -eo pipefail

BEFORE=$(mktemp)
AFTER=$(mktemp)

cleanup() {
  rm -f "${BEFORE}" "${AFTER}"
}

trap cleanup EXIT

function compare(){
    IMG=$1
    BEFORE_TAG=$2
    AFTER_TAG=$3

    DIRS="${DIRS:-/usr/local/sbin /usr/local/bin /usr/sbin /usr/bin /sbin /bin}"
    echo "" > "${BEFORE}"
    echo "" > "${AFTER}"

    for dir in $DIRS; do
        docker run --rm --entrypoint ls "${IMG}:${BEFORE_TAG}" "${dir}" >> "${BEFORE}"
        docker run --rm --entrypoint ls "${IMG}:${AFTER_TAG}" "${dir}" >> "${AFTER}"
    done

    echo "Missing files on new ${IMG}:${AFTER_TAG}:"
    diff -y "${BEFORE}" "${AFTER}" | grep "<" | awk '{ print $1 }' | sort -u
}

if [ $# -lt 3 ]; then
  echo "usage: $0 <IMAGE> <TAG1> <TAG2>" >&2
  exit 1
fi

compare $1 $2 $3