df

show disk space

ex: df  -h:

Filesystem            Size  Used Avail Use% Mounted on

/dev/hda3             9.9G  7.0G  2.4G  75% /

udev                  8.0G  132K  8.0G   1% /dev

objdump

show assembly of program:
ex:

objdump -D test.o

fsck

check file system