Extracting MacOS pkg files on Linux

xpkg.sh

#!/bin/bash
#
# Super basic MacOS .pkg file extractor using p7zip & cpio
# @yellowcrescent
#
# Usage: xpkg.sh MyPkg.pkg /path/to/output/dir
#

ZBIN=7z
PLFILE="Payload~"
SRCPKG="$1"
OUTDIR=$(readlink -m "${2:-.}")

if [[ -z "${SRCPKG}" || "${SRCPKG}" == "-h" || "${SRCPKG}" == "--help" ]]; then
  echo "usage: $0 INPUT_PKG.pkg [OUTPUT_DIR]"
  exit 2
fi

if [[ ! $(which ${ZBIN}) ]]; then
  echo "7-zip is not installed (command ${ZBIN} not found). Try installing p7zip-full or similar package."
  exit 3
fi

# Requires the full version of 7-zip (eg. "p7zip-full" or similar)
$ZBIN x "${SRCPKG}" "-o${OUTDIR}"
if [[ "$1" != 0 ]]; then
  echo "Extraction failed."
fi

# Extract payload via cpio if it exists
CPIOFILE="${OUTDIR}/${PLFILE}"
if [[ -e "${CPIOFILE}" ]]; then
  cpio -idmv -F "${CPIOFILE}" -D "${OUTDIR}"
fi

echo "Complete."