C＃中连续读取文件 [英] c# continuously read file

问题描述

我想读的文件不断像GNU尾巴-f参数。我需要它来住读取日志文件。
什么是做正确的方式？

I want to read file continuously like GNU tail with "-f" param. I need it to live-read log file. What is the right way to do it?

推荐答案

您想以二进制方式打开的FileStream 。定期，力求文件减去1024字节（或其他）的结尾，然后阅读到最后输出。这是-f 如何尾工作。

You want to open a FileStream in binary mode. Periodically, seek to the end of the file minus 1024 bytes (or whatever), then read to the end and output. That's how tail -f works.

问题的答案：

二进制，因为它是困难的，如果你读它作为文本随机访问文件。你必须自己做二进制到文本的转换，但它并不困难。 （见下文）

Binary because it's difficult to randomly access the file if you're reading it as text. You have to do the binary-to-text conversion yourself, but it's not difficult. (See below)

1024个字节，因为它是一个很好的便利数，应该处理10或15行文字。通常

1024 bytes because it's a nice convenient number, and should handle 10 or 15 lines of text. Usually.

下面是打开文件，读的是最后1024个字节，并将其转换为文本的例子：

Here's an example of opening the file, reading the last 1024 bytes, and converting it to text:

static void ReadTail(string filename)
{
    using (FileStream fs = File.Open(filename, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
    {
        // Seek 1024 bytes from the end of the file
        fs.Seek(-1024, SeekOrigin.End);
        // read 1024 bytes
        byte[] bytes = new byte[1024];
        fs.Read(bytes, 0, 1024);
        // Convert bytes to string
        string s = Encoding.Default.GetString(bytes);
        // or string s = Encoding.UTF8.GetString(bytes);
        // and output to console
        Console.WriteLine(s);
    }
}

请注意，你必须用 FileShare.ReadWrite 打开，因为你试图读取一个文件，该文件是当前打开的另一个进程的写作。

Note that you must open with FileShare.ReadWrite, since you're trying to read a file that's currently open for writing by another process.

另外请注意，我用 Encoding.Default ，这在美国/英语和大多数西欧语言将是一个8位字符编码。如果该文件是写在一些其他的编码（如UTF-8或其他统一code编码），这可能是字节将无法正确转换为字符。你必须通过确定的编码来处理，如果你认为这将是一个问题。搜索堆栈溢出的信息有关确定文件的文本编码。

Also note that I used Encoding.Default, which in US/English and for most Western European languages will be an 8-bit character encoding. If the file is written in some other encoding (like UTF-8 or other Unicode encoding), It's possible that the bytes won't convert correctly to characters. You'll have to handle that by determining the encoding if you think this will be a problem. Search Stack overflow for info about determining a file's text encoding.

如果您想定期做到这一点（每15秒，例如），您可以设置经常只要你想调用 ReadTail 方法的计时器。可以通过在节目的开始打开文件仅一次优化事情有点。这是给你的。

If you want to do this periodically (every 15 seconds, for example), you can set up a timer that calls the ReadTail method as often as you want. You could optimize things a bit by opening the file only once at the start of the program. That's up to you.

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