 of the specified resource is printed.  If
    no option is given, then -f is assumed.
    
    Values are in 1024-byte increments, except for -t, which is in seconds,
    -p, which is in increments of 512 bytes, and -u, which is an unscaled
    number of processes.
    
    Exit Status:
    Returns success unless an invalid option is supplied or an error occurs.