iOS 获取手机剩余空间大小

+ (NSString *)freeDiskSpaceInBytes
{
    struct statfs buf;
    long long freespace = -1;
    if(statfs("/var", &buf) >= 0)
    {
        freespace = (long long)(buf.f_bsize * buf.f_bfree);
    }
    return [NSString stringWithFormat:@"%qi" ,freespace/1024/1024];
}