So, following the suggestion in #201, let's start to discuss file system access API. In order to keep it focused, I'd suggest to start with the directory related operations first. My proposal:

open_directory(dirname, dirdesc, status): Opens a directory and returns a descriptor

type(dirdesc_t): Type containing the data of an opened directory

dirdesc_t%get_next(): Returns the next entry in the open directory or "" if
there are no more entries.

make_directory(dirname, parents, status): Makes a directory. If parents is .true.
also parent directories are created in case they do not exist yet.

remove_directory(dirname, content, status): Removes a directory. If content is
.true. also the directory content is removed (recursive delete).

change_directory(dirname, status): Changes to the given directory

get_working_dir() -> char(:), allocatable: Returns the current working directory.

is_dir(fname) -> logical: GIve .true. if fname is a directory.

A few notes:

• The functionality above can be easily realized with a libc-interface (should work on all POSIX systems) and a bit of C-code. The big question is Windows, as I have no clue how to implement this functionality on WIndows.

• As for error handling we could have a status argument. I'd argue for having a derived type type(status_t) containg the result of the operation (OK/Error) and a string with the error message in case of error. Whether the status argument should be optional or not is open for discussions.