Disk Usage related Commands to monitor Disk space

1)Disk Usage on all mounts
df -h -T

Filesystem Type Size Used Avail Use% Mounted on
/dev/sda1 ext3 2.9G 785M 2.0G 29% /
/dev/sda7 ext3 57G 9.3G 45G 18% /cust
/dev/sda6 ext3 2.0G 82M 1.8G 5% /lc
none tmpfs 5.7G 0 5.7G 0% /dev/shm
/dev/sda5 ext3 2.0G 33M 1.8G 2% /tmp
/dev/sda3 ext3 2.0G 64M 1.8G 4% /var

2)prints just one line with the total size of the directory, the below example show the size of the /usr/IBM/Websphere WebSphere Portal Server directory.
du -ch | grep total

bash-2.05b# du -ch | grep total
6.3G total