According to the documentation, there's no way to directly write back a GKeyFile to its/another file. The only way seems now to write a custom function using g_key_file_to_data() and such as g_file_set_contents().

I think writing a GKeyFile to a file is common enough to consider adding a simple g_key_file_to_file() or such function directly in the GLib. Moreover, there's a function to load a configuration directly from a file, I think it would be more consistent to have a function to do the opposite.

I'll attach a small patch (based on 2.16.6) with a naive but functional implementation.

Regards,
Colomban W.