$ du // This gives you a list of directories that exist in the current directory along with their sizes.
$ du app/ // This gives you a list of directories that exist in the specified directory app/ along with their sizes.
$ du -h // Better output, '-h' stands for human readable format. So the sizes of the files / directories are this time suffixed with a 'k' if its kilobytes and 'M' if its Megabytes and 'G' if its Gigabytes.
$ du -ah // Lists file size also and in human readable format.
$ du -c // This gives only total size of the directories and the grand total.
$ du -ch | grep total // This gives the total size
$ df
$ df // This shows the free space in kilobytes
Filesystem 1K-blocks Used Available Use% Mounted on
rootfs 40316280 5077616 34829228 13% /
udev 1474708 0 1474708 0% /dev
tmpfs 1482684 9024 1473660 1% /dev/shm
tmpfs 1482684 712 1481972 1% /run
/dev/sda6 40316280 5077616 34829228 13% /
tmpfs 1482684 0 1482684 0% /sys/fs/cgroup
tmpfs 1482684 0 1482684 0% /media
/dev/sda8 46003208 9172500 34493840 22% /home
/dev/sda6 40316280 5077616 34829228 13% /tmp
/dev/sda6 40316280 5077616 34829228 13% /var/tmp
/dev/sda8 46003208 9172500 34493840 22% /home
$ df -h // With human readable format
$ df -h | grep /dev/sda8
/dev/sda8 44G 8.8G 33G 22% /home
/dev/sda8 44G 8.8G 33G 22% /home
$ df -h | grep /dev/sda8 | cut -c 41-43 // This command gives the usage percentage of /dev/sda8
22%
22%
Reference: http://www.codecoffee.com/tipsforlinux/articles/22.html