size of directory reported by ls

Question

I understand the size reported by ls corresponds with number of inodes inside the directory, not their actual size.

I have noticed peculiar behavior, when displaying directory size with ls. Here is how to quickly reproduce it:

first create empty directory, the size reported by ls is 4096 (as expected)

mkdir test
ll -d test/
drwx------ 2 root root 4,096  2015-Dec-29  22:22:36  test/

create 10,000 files inside. Size reported is now 167,936

touch test/{1..9999}
ll -d test/
drwx------ 2 root root 167,936  2015-Dec-29  22:23:24  test/

remove all files. Size should decrease back to 4096

rm test/*
ll -d test/
drwx------ 2 root root 167,936  2015-Dec-29  22:23:59  test/

But the size is still reported as 167,936.

why?

can somebody explain this?

Answer 1

Generally, directory files are not cleaned up - their space usually is small enough (compared to their contents) that it's not effective to do this (particularly when they might grow again). Finding an authoritative answer for this might be hard... Forum comments are easy:

• Shrink/reset directory size?
• Linux directories do not shrink automatically also gives some insight.
• Why directory with large amounts of entries does not shrink in size after entries are removed? provides a Linux-specific authoritative answer