[NTG-context] Create a directory using tex

[Aditya Mahajan]

On Tue, 29 Aug 2006, Taco Hoekwater wrote:

> Aditya Mahajan wrote:
>> Hi,
>>
>>   I want to create a macro that writes files in a sub directory.
>> If the directory is already created, things work fine. However, if the
>> directory is not there, tex complains
>>
>> ! I can't write on file ....
>>
>> Please type another output file name:
>>
>>   Is there a way I can ask tex to create a directory if one does not
>> exist?
>
> Not with TeX, but you can use \write18 or \installprogram  to run a
> system command.

Can I ask TeX to check if a directory exists or is writable. I want it 
to give an informative message if the directory does not exist.

Or is there a way to check if a file is writable, so that I can do

\doiffilewritable{dir/tempfile}{\donothing}{\message{Warning}{Please 
create directory 'dir' \endinput}

Aditya