Helper for comparing what macOS user defaults change between 2 points in time

read_defaults.sh

#!/usr/bin/env nix-shell
#!nix-shell -i bash -p bash

set -euo pipefail

readonly _mode="${1:-}"
case "$_mode" in
  'pre' | 'post' | 'compare')
    readonly mode="${_mode}"
    ;;
  *)
    echo "Unsupported mode [${_mode}]. Must be one of [pre, post, compare]"
    exit 1
esac

if [ "${mode}" == 'compare' ]; then
  readonly target="${2:-}"
  if [ -z "${target}" ]; then
    echo "Must provide a comparison target"
    exit 1
  fi
fi

readonly basedir="$HOME/.local/share/apple_defaults_helper"

containsElement () {
  local e match="$1"
  shift
  for e; do [[ "$e" == "$match" ]] && return 0; done
  return 1
}

setup() {
  mkdir -p "${basedir}"/{pre,post}
  rm -rf "${basedir}/${mode}"/*
}

write_all_domains() {
  local -r targetdir="${1}"

  local -r ignored_domains=( ContextStoreAgent com.apple.xpc.activity2 )

  echo "--------------------"
  echo "Reading defaults"
  echo "--------------------"

  orig_ifs=$IFS
  IFS=','

  for domain in $( defaults domains | sort ); do
    local trimmed_domain=$( echo $domain | xargs )
    local destfile="${targetdir}/default__${trimmed_domain}"

    if containsElement "${trimmed_domain}" "${ignored_domains[@]}"; then
      continue
    fi

    (defaults read $trimmed_domain 2>/dev/null || echo 'unknown') > "${destfile}"
    local sum=$( md5 -q "${destfile}" )
    echo "$trimmed_domain: $sum" >> "${targetdir}/default__md5sums"
  done

  IFS=$orig_ifs

  echo "Done"
}

write_all_preferences() {
  local -r targetdir="${1}"

  local -r ignored_prefs=( com.apple.TimeMachine.plist com.apple.apsd.plist com.apple.Bluetooth.plist com.apple.networkextension.uuidcache.plist )

  echo
  echo "--------------------"
  echo "Reading preferences"
  echo "--------------------"

  for plist in /Library/Preferences/*.plist; do
    local base_plist=$( basename $plist )
    local destfile="${targetdir}/plist__${base_plist}"

    if containsElement "${base_plist}" "${ignored_prefs[@]}"; then
      continue
    fi

    /usr/libexec/PlistBuddy -c "Print" "${plist}" > "${destfile}" || (echo "Error reading ${base_plist}"; continue)
    local sum=$( md5 -q "${destfile}" )
    echo "$base_plist: $sum" >> "${targetdir}/plist__md5sums"
  done

  echo "Done"
}

do_compare() {
  echo
  echo "--------------------"
  echo "comparing defaults"
  echo "--------------------"
  (diff --side-by-side --suppress-common-lines "${basedir}/pre/default__md5sums" "${basedir}/post/default__md5sums" && echo "No changes") || true

  echo
  echo "--------------------"
  echo "comparing plists"
  echo "--------------------"
  (diff --side-by-side --suppress-common-lines "${basedir}/pre/plist__md5sums" "${basedir}/post/plist__md5sums" && echo "No changes") || true
}

main() {
  if [ "${mode}" == "compare" ]; then
    if [ "${target##*.}" == "plist" ]; then
      diff --text --side-by-side "${basedir}/pre/plist__${target}" "${basedir}/post/plist__${target}"
    else
      diff --text --side-by-side "${basedir}/pre/default__${target}" "${basedir}/post/default__${target}"
    fi
  else
    setup

    write_all_domains "${basedir}/${mode}"
    write_all_preferences "${basedir}/${mode}"

    if [ "${mode}" == "post" ]; then
      do_compare
    fi
  fi

  echo
  echo 'Done.'
}

main