Bash wrapper to conditionally apply patch

safepatch.sh

#!/usr/bin/env bash

# first argument is a patch file
if [ $# -eq 0 ]; then
  echo "No arguments supplied. Aborting."
  exit 0
fi

PATCH_FILE=$1

# try to apply patch and see if it was already applied
STAT=$(patch -p0 -N --dry-run --silent < "${PATCH_FILE}" 2>&1>/dev/null; echo $?)
if [ ${STAT} -eq 0 ]; then
  # actually apply patch if it wasn't applied yet
  patch -p0 -N < "${PATCH_FILE}"
else
  echo "Patch was already applied: ${PATCH_FILE}"
  exit 0
fi