Something

printf("Disk size: %lu [%luMB] [%3luGB] \t Disk usage : %lu [%luMB] [%3luGB] \t Free space %lu [%luMB] [%3luGB]\n", disk_size,disk_size/(1024*1024), disk_size/(1024*1024*1024), used, used/(1024*1024),used/(1024*1024*1024), free, free/(1024*1024), free/(1024*1024*1024));