Function mpv_command_ret 

pub unsafe extern "C" fn mpv_command_ret(
    ctx: *mut mpv_handle,
    args: *mut *const c_char,
    result: *mut mpv_node,
) -> c_int

This is essentially identical to mpv_command() but it also returns a result.

Does not use OSD and string expansion by default.

@param[in] args NULL-terminated list of strings. Usually, the first item is the command, and the following items are arguments. @param[out] result Optional, pass NULL if unused. If not NULL, and if the function succeeds, this is set to command-specific return data. You must call mpv_free_node_contents() to free it (again, only if the command actually succeeds). Not many commands actually use this at all. @return error code (the result parameter is not set on error)