Alexander Steinböck <bts@bts.grml.org>:
> > As per susv3, id only needs to support short options like '-u'.
> > '--user' is a GNU extension. IOW: if you want to enhance
> > portability, stick to sus.
> Thanks for the hint.
> And done.
[...]
> -if [ $UID != 0 ]; then
> +if [ $(id -u) -ne 0 ]; then
[...]
> -   exit -1
> +   exit 1
[...]
> -if [[ $1 == '-force' ]]; then
> +if [ $1 = '-force' ]; then
[...]
> -if [ $UID != 0 ]; then
> +if [ $(id -u) -ne 0 ]; then
[...]
> -   exit -1
> +   exit 1
[...]
> -if [[ $1 == '-force' ]]; then
> +if [ $1 = '-force' ]; then

ACK.