There are so many commands of Ubuntu, we just need to know useful and high-frequency commands. I have collected a little common commands which may be useful for you in the future.
Check the size of directory
sudo df -h #show the current info of partitions
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 40G 2.9G 35G 8% /
udev 2.0G 4.0K 2.0G 1% /dev
tmpfs 790M 864K 789M 1% /run
none 5.0M 0 5.0M 0% /run/lock
none 2.0G 152K 2.0G 1% /run/shm
none 100M 40K 100M 1% /run/user
sudo du /home/pinxiong/ --max-depth=1 -h #show the first-level sub-directory info in directory '/home/pinxiong'
4.0K /home/pinxiong/Templates
43M /home/pinxiong/.mozilla
4.0K /home/pinxiong/Pictures
32K /home/pinxiong/.gconf
32K /home/pinxiong/.pulse
4.0K /home/pinxiong/Downloads
12K /home/pinxiong/.mission-control
444K /home/pinxiong/.local
120K /home/pinxiong/.config
4.0K /home/pinxiong/Public
4.0K /home/pinxiong/Videos
4.0K /home/pinxiong/Documents
12K /home/pinxiong/.dbus
716K /home/pinxiong/.cache
4.0K /home/pinxiong/Music
4.0K /home/pinxiong/Desktop
8.0K /home/pinxiong/.gnome2
44M /home/pinxiong/
sudo du /home/pinxiong/ -sh #show the size of directory '/home/pinxiong'
44M /home/pinxiong/