root@powerslave:/usr/ports/x11/kde3# df -h .
Filesystem     Size    Used   Avail Capacity  Mounted on
/dev/ad0s1f     31G     28G    753M    97%    /usr
root@powerslave:/usr/ports/x11/kde3# make clean
[...]
root@powerslave:/usr/ports/x11/kde3# df -h .
Filesystem     Size    Used   Avail Capacity  Mounted on
/dev/ad0s1f     31G     25G    3.8G    87%    /usr