How to list directory size of all child directories?
The simplest is:
du -h --max-depth=1 parent
This will show all sizes of the children of parent
If you also want the grandchildren, you can do
du -h --max-depth=2 parent
If you want the whole family
du -h parent
All these will just summarize the total directory size of each subdirectory up to a given level (except the last, it will give for all)
If you don't want the content of the subdirectories, add the -S
flag.