You `open()` a directory, and `getdents()` takes that file descriptor as input. “These are not the interfaces you are interested in. Look at readdir(3)

You `open()` a directory, and `getdents()` takes that file descriptor as input. “These are not the interfaces you are interested in. Look at readdir(3) for the POSIX-conforming C library interface.” — getdents manpage