使用 FileSystemWatcher 从文件中获取新行

发布于 2024-07-29 16:54:19 字数 809 浏览 7 评论 0原文

我正在观看一个包含以下代码的文件：

        [..]
        FileSystemWatcher watcher = new FileSystemWatcher();
        watcher.Path = @"C:\";
        watcher.Filter = "t.log";
        watcher.Changed += new FileSystemEventHandler(watcher_Changed);
        watcher.EnableRaisingEvents = true;

        private static void watcher_Changed(object sender, FileSystemEventArgs e)
        {
            Console.WriteLine("Changed!");
        }
        [..]

这有效。现在，假设文件 t.log 的内容是：

row 1
row 2
row 3
row 4

当我向文件添加（并保存）几行时，文件变成这样：

row 1
row 2
row 3
row 4
row 5
row 6

如何检索添加的行是“第 5 行”和“第 6 行” “？

请注意，该文件可能非常大，因此不能将其内容保留在内存中并与新版本进行比较。同样，存储最后读取行的值并从该行开始计数也是不可能的，因为这会迫使我每次都读取整个文件，而且可能存在具有相同值的行。

任何帮助真的很感激。

原文

I'm watching a file with the following code:

        [..]
        FileSystemWatcher watcher = new FileSystemWatcher();
        watcher.Path = @"C:\";
        watcher.Filter = "t.log";
        watcher.Changed += new FileSystemEventHandler(watcher_Changed);
        watcher.EnableRaisingEvents = true;

        private static void watcher_Changed(object sender, FileSystemEventArgs e)
        {
            Console.WriteLine("Changed!");
        }
        [..]

This works. Now, supposed that the content if file t.log is:

row 1
row 2
row 3
row 4

When I add to the file (and save) a couple of lines and the file becomes this:

row 1
row 2
row 3
row 4
row 5
row 6

How can I retrieve that the added lines are "row 5" and "row 6"?

Mind that the file may be very large, so having its content in memory and making a diff with the new version is not an option. Similarly, storing the value of the last read line and count from that on is not possible too, as it would force me to read the whole file every time, plus there may be lines with the same value.

Any help really appreciated.

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烦人精 2024-08-05 16:54:19

如果它是始终附加的日志，您可以保留文件大小和更改：

using (FileStream fs = new FileStream("t.log", FileAccess.Read))
{
  fs.Seek(previousSize, SeekOrigin.Begin);
  //read, display, ...
  previousSize = fs.Length;
}

If it's a log, always appended, you can keep the file size and on change :

using (FileStream fs = new FileStream("t.log", FileAccess.Read))
{
  fs.Seek(previousSize, SeekOrigin.Begin);
  //read, display, ...
  previousSize = fs.Length;
}

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