How to get the file size given a path?

If you want only file size with bytes just use,

unsigned long long fileSize = [[[NSFileManager defaultManager] attributesOfItemAtPath:yourAssetPath error:nil] fileSize];

NSByteCountFormatter string conversion of filesize (from Bytes) with precise KB, MB, GB ... Its returns like 120 MB or 120 KB

NSError *error = nil;
NSDictionary *attrs = [[NSFileManager defaultManager] attributesOfItemAtPath:yourAssetPath error:&error];
if (attrs) {
    NSString *string = [NSByteCountFormatter stringFromByteCount:fileSize countStyle:NSByteCountFormatterCountStyleBinary];
    NSLog(@"%@", string);
}

In Swift 3.x and above you can use:

do {
    //return [FileAttributeKey : Any]
    let attr = try FileManager.default.attributesOfItem(atPath: filePath)
    fileSize = attr[FileAttributeKey.size] as! UInt64

    //or you can convert to NSDictionary, then get file size old way as well.
    let attrDict: NSDictionary = try FileManager.default.attributesOfItem(atPath: filePath) as NSDictionary
    fileSize = dict.fileSize()
} catch {
    print("Error: \(error)")
}