create file in directory without x permission set on directory : How?

Question

From this page, http://content.hccfl.edu/pollock/aunix1/filepermissions.htm, I understand that I need the +w bit set in a directory to create a new file and +x bit to cd into it/access its inode. So far, so good. But, I can't use vi/cat/nano/echo etc to do stuff like:

echo hello > dir/file

because I can't access inode of dir. My question is, how do I create/delete/rename a new file in dir if I can't access its inode ? Can I edit the directory structure using

vi dir

and create/edit/rename a new file? Is there a tutorial to do so ?

Answer 1

If you don't have +x even if you have +w, you can not create new entries in the directory, neither files nor directories.

Answer 2

The x permission on directories is a "lookup" permission. It is needed to get hold of dentry in the directory by name.

Since each and every filesystem operation starts with a lookup on the target path, you have absolutely no access to content of a directory where you don't have x permission. There is thus no point in having w without x, because creating dentries in the directory requires lookup permission there.

The fact that you can't cd is kind of side-effect, because it looks up . inside the directory, not just the directory itself (you still can stat the directory).