df
#Bytes on device: +\d+ [GMK]?bytes
#Unused bytes on device: +\d+ [GMK]?bytes
#Unused available bytes on device: \d+ [GMK]?bytes
#Bytes per allocation unit: +\d+ [GMK]?bytes
df nosuchpath
#.*file does not exist.*
df ""
#Bytes on device: +\d+ [GMK]?bytes
#Unused bytes on device: +\d+ [GMK]?bytes
#Unused available bytes on device: \d+ [GMK]?bytes
#Bytes per allocation unit: +\d+ [GMK]?bytes
