dateId(id, 'id');
      if (typeof id === 'number') id |= 0;
      // Result is 0 on success, 1 if credential is unknown.
      const result = method(id);
      if (result === 1) {
        throw new ERR_UNKNOWN_CREDENTIAL(type, id);
      }
    };
  }

  function validateId(id, name) {
    if (typeof id === 'number') {
      validateUint32(id, name);
    } else if (typeof id !== 'string') {
      throw new ERR_INVALID_ARG_TYPE(name, ['number', 'string'], id);
    }
  }

  return {
    initgroups,
    setgroups,
    setegid: wrapIdSetter('Group', _setegid),
    seteuid: wrapIdSetter('User', _seteuid),
    setgid: wrapIdSetter('Group', _setgid),
    setuid: wrapIdSetter('User', _setuid)
  };
}

// Cache the working directory to prevent lots of lookups. If the working
// directory is changed by `chdir`, it'll be updated.
let cachedCwd = '';

function wrappedChdir(directory) {
  validateString(directory, 'directory');
  rawMethods.chdir(directory);
  // Mark cache that it requires an update.
  cachedCwd = '';
}

function wrappedUmask(mask) {
  if (mask !== undefined) {
    mask = parseFileMode(mask, 'mask');
  }
  return rawMethods.umask(mask);
}

function wrappedCwd() {
  if (cachedCwd === '')
    cachedCwd = rawMethods.cwd();
  return cachedCwd;
}