我有多数民众赞成追加到随着时间的推移一个文本文件，并定期我想截断下来到一定规模，如10MB，但保持最后10MB，而不是第一个。

I have a text file that's appended to over time and periodically I want to truncate it down to a certain size, e.g. 10MB, but keeping the last 10MB rather than the first.

有什么聪明的方法来做到这一点？我猜我应该寻求正确的点，从那里读入一个新的文件，删除旧文件并重新命名新文件到旧名称。更好的想法或例如code？理想情况下我也不会读取整个文件到内存，因为该文件可能是很大的。

Is there any clever way to do this? I'm guessing I should seek to the right point, read from there into a new file, delete old file and rename new file to old name. Any better ideas or example code? Ideally I wouldn't read the whole file into memory because the file could be big.

请使用log4net的任何建议等。

Please no suggestions on using Log4Net etc.

推荐答案

如果你没问题，光看过去的10MB内存，这应该工作：

If you're okay with just reading the last 10MB into memory, this should work:

using(MemoryStream ms = new MemoryStream(10 * 1024 * 1024)) {
    using(FileStream s = new FileStream("yourFile.txt", FileMode.Open, FileAccess.ReadWrite)) {
        s.Seek(-10 * 1024 * 1024, SeekOrigin.End);
        s.CopyTo(ms);
        s.SetLength(10 * 1024 * 1024);
        s.Position = 0;
        ms.CopyTo(s);
    }
}