$out = exec("/bin/df");

/dev/hda5 19228276  14838700   3412828  82% /home/martyn/hda5

$out = system("/bin/df");

Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda1             17140848  15318284    951844  95% /
varrun                 1298328       164   1298164   1% /var/run
varlock                1298328         4   1298324   1% /var/lock
procbususb               10240       460      9780   5% /proc/bus/usb
udev                     10240       460      9780   5% /dev
devshm                 1298328         0   1298328   0% /dev/shm
/dev/hda4            115449964 102753568   6831868  94% /home/martyn/hda4
/dev/hdd2            142876628 132907772   5614200  96% /home/martyn/hdd2
/dev/hda5             19228276  14838700   3412828  82% /home/martyn/hda5
/dev/hda5             19228276  14838700   3412828  82% /home/martyn/hda5