#!/usr/bin/env bash
# Exit 0 when PATTERN is absent.
# Exit 1 when PATTERN is present.
# Exit 64 on usage error.
set -u

if [ "$#" -lt 2 ]; then
  echo "usage: router-grep-absent PATTERN FILE..." >&2
  exit 64
fi

pattern="$1"
shift

grep -E -- "$pattern" "$@" >/dev/null 2>&1
rc="$?"

case "$rc" in
  0) exit 1 ;;   # found => expected absence violated
  1) exit 0 ;;   # not found => OK
  *) exit "$rc" ;;
esac
