How to detect a CD Drive / write permissions?

[Tiemo Hollmann TB]

Hello,

didn't found the answer in the archives, though it seems to be very
standard.

1. How to test If I have write permissions on a dir?

Is the appropriate approach to try to write a file on the wanted dir and if
it fails I know I can't? Or is there a Rev function to ask?

2. How can I detect, if a volume is a HD or CD/DVD?

If I know that I don't have write permissions with the above test, I still
don't know, if it is a permission problem (what I could ask the user for) or
if I am on a CD/DVD (where I don't want to ask the user)? How can I
differentiate that, I didn't find a Rev function which tells me something
about the kind of drives?

Thanks for any hints and approaches

Tiemo