Deletes the file whose name is specified in filename.
This is an operation performed directly on a file identified by its filename; No streams are involved in the operation.
Proper file access shall be available.
C string containing the name of the file to be deleted.
Its value shall follow the file name specifications of the running environment and can include a path (if supported by the system).
If the file is successfully deleted, a zero value is returned.
On failure, a nonzero value is returned.
On most library implementations, the errno variable is also set to a system-specific error code on failure.