[SOLVED] testing if a directory is empty

it would have been approaching half as many I/O operations for a lot of data i have (lots of empty directories).

Originally Posted by Skaperen if there was a way to determine that a directory is empty from its inode,

Only when
- the file system is ext?
- the directory has NEVER been used (there never were any names stored IN them)
the directory size is 48 bytes (only the . and .. entries), because that's the way "mkdir" creates them.

But as used directories, even after removing all files in them, never shrink their size in an ext? fs you cannot see from its I-node if they are empty (only how large they neede to be at their most full contents). And as extending the directory size goes to the next block size (often 4 KB) a size of "that block size" or a multiple doesn't tell you anything about the current content OF that directory.

EDIT: I was wrong, ext? does NOT create directories with an 48 bytes size.

lt2a/forums /home/forums 23> ls -dl foo
/bin/ls: cannot access 'foo': No such file or directory
lt2a/forums /home/forums 24> mkdir foo
lt2a/forums /home/forums 25> ls -dl foo
drwxr-xr-x 2 forums forums 4096 Mar 27 16:08 foo
lt2a/forums /home/forums 26> fgrep ' /home ' /proc/mounts
/dev/sda4 /home ext4 rw,relatime 0 0
lt2a/forums /home/forums 27>

maybe you are confusing ext4 with btrfs. or was that reiserfs?

Originally Posted by Skaperen maybe you are confusing ext4 with btrfs. or was that reiserfs?

No, reiserfs does shrink directory files as the tree is completely REwritten after changes.

On a ext3 fs
 % mkdir new
 % ls -dl new
drwxr-xr-x 2 hartman beheer 4096 2020-03-27 22:32 new
and a reiserfs one
 % mkdir new
 % ls -dl new
drwxr-xr-x 2 hartman beheer 48 2020-03-27 22:34 new
after putting some files in it
drwxr-xr-x 2 hartman beheer 240 2020-03-27 22:35 new
and removing them again
drwxr-xr-x 2 hartman beheer 48 2020-03-27 22:36 new

so you're right for ext3 at least (and I was wrong - I tested it too in ext2), but in reiserfs a directory size of 48 always means the directory is empty
but on ext? the directory size is a multiple of the blocksize for that fs (correction to my previous MSG), independant of how many filenames are IN it.

And thanks for the reaction, I do make mistakes sometimes!