For the /dev/fd feature, for any user to be able to access these fiels, their permissions must be rw-rw-rw. Some programs that create an output file delete the file first, in case it already exist, ignoring the return code:

unlink (path);

If ((fd = creat (path, FILE_MODE)) < 0)

printf (error );

What happens if path is /dev/fd/1?