df - Disk free space
df
Df prints out the amount of free space on all of the mounted file systems. The reported numbers are in 512-byte disk blocks. The percentage of disk space used is also given.
A sample display looks like this:
Dev Blocks Free Used Used% Volume ------------------------------------------------- 3.2 127 100 27 21% /ram 7.1 41616 33302 8314 20% /a 6.1 280 185 95 34% /z
Df supports output redirection into files.