blocks|key|1135122|text|您可以使用FileSystemWatcher类，它可以为文件系统上发生的不同事件发送通知。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1135123|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/system.io.filesystemwatcher.aspx^0|5|H|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

You could use the <a href="http://msdn.microsoft.com/en-us/library/system.io.filesystemwatcher.aspx" rel="nofollow">FileSystemWatcher</a> class which can send notifications for different events happening on the file system like file changed.

blocks|key|1135165|text|如果你只是想找一个工具来做这件事，那就看看Bare+tail的免费版本吧|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1135166|entityMap|0|LINK|mutability|MUTABLE|url|http://baremetalsoft.com/baretail/^0|L|9|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

If you are just looking for a tool to do this then check out free version of <a href="http://baremetalsoft.com/baretail/" rel="nofollow">Bare tail</a>

blocks|key|1135253|text|您希望以二进制模式打开FileStream。定期查找到文件末尾减去1024字节(或其他任何字节)，然后读取到末尾并输出。这就是tail+-f的工作原理。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1135254|您的问题的答案：|1135255|二进制，因为如果您将其作为文本读取，则很难随机访问该文件。您必须自己完成二进制到文本的转换，但这并不困难。(见下文)|1135256|1024字节，因为这是一个非常方便的数字，应该可以处理10到15行文本。通常是这样。|1135257|以下是打开文件、读取最后1024字节并将其转换为文本的示例：|1135258|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);
++++}
}|code-block|syntax|javascript|1135259|请注意，您必须使用FileShare.ReadWrite打开，因为您正在尝试读取当前由另一个进程打开以供写入的文件。|1135260|还要注意，我使用的是Encoding.Default，在美国/英语和大多数西欧语言中，它都是8位字符编码。如果文件是以其他编码(如UTF-8或其他Unicode编码)编写的，则字节可能无法正确转换为字符。如果您认为这将是一个问题，那么您必须通过确定编码来处理它。有关确定文件的文本编码的信息，请搜索堆栈溢出。|1135261|如果您希望定期执行此操作(例如，每15秒)，则可以设置一个计时器，该计时器可以根据需要随时调用ReadTail方法。你可以通过在程序开始时只打开文件一次来优化它。那随你的便。|1135262|entityMap^0|B|A|1R|7|0|0|0|0|0|0|9|J|0|A|G|0|1B|8|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|15|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|16|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|17|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|18|8|@]|D|@]|E|$]]|$1|N|3|O|5|P|7|19|8|@]|D|@]|E|$Q|R]]|$1|S|3|T|5|6|7|1A|8|@$9|1B|A|1C|B|C]]|D|@]|E|$]]|$1|U|3|V|5|6|7|1D|8|@$9|1E|A|1F|B|C]]|D|@]|E|$]]|$1|W|3|X|5|6|7|1G|8|@$9|1H|A|1I|B|C]]|D|@]|E|$]]|$1|Y|3|-4|5|6|7|1J|8|@]|D|@]|E|$]]]|Z|$]]

You want to open a <code>FileStream</code> 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 <code>tail -f</code> works.

Answers to your questions:

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

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

<pre><code>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);
 }
}
</code></pre>

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

Also note that I used <code>Encoding.Default</code>, 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.

If you want to do this periodically (every 15 seconds, for example), you can set up a timer that calls the <code>ReadTail</code> 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.

blocks|key|1135274|text|private+void+button1_Click(object+sender,+EventArgs+e)
{
++++if+(folderBrowserDialog.ShowDialog()+==+DialogResult.OK)
++++{
++++++++path+=+folderBrowserDialog.SelectedPath;
++++++++fileSystemWatcher.Path+=+path;

++++++++string[]+str+=+Directory.GetFiles(path);
++++++++string+line;
++++++++fs+=+new+FileStream(str[0],+FileMode.Open,+FileAccess.Read,+FileShare.ReadWrite);
++++++++tr+=+new+StreamReader(fs);+

++++++++while+((line+=+tr.ReadLine())+!=+null)
++++++++{

++++++++++++listBox.Items.Add(line);
++++++++}


++++}
}

private+void+fileSystemWatcher_Changed(object+sender,+FileSystemEventArgs+e)
{
++++string+line;
++++line+=+tr.ReadLine();
++++listBox.Items.Add(line);++
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1135275|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>private void button1_Click(object sender, EventArgs e)
{
 if (folderBrowserDialog.ShowDialog() == DialogResult.OK)
 {
 path = folderBrowserDialog.SelectedPath;
 fileSystemWatcher.Path = path;

 string[] str = Directory.GetFiles(path);
 string line;
 fs = new FileStream(str[0], FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
 tr = new StreamReader(fs); 

 while ((line = tr.ReadLine()) != null)
 {

 listBox.Items.Add(line);
 }


 }
}

private void fileSystemWatcher_Changed(object sender, FileSystemEventArgs e)
{
 string line;
 line = tr.ReadLine();
 listBox.Items.Add(line); 
}
</code></pre>

blocks|key|1135311|text|使用FileSystemWatcher的更自然的方法|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1135312|++++var+wh+=+new+AutoResetEvent(false);
++++var+fsw+=+new+FileSystemWatcher(".");
++++fsw.Filter+=+"file-to-read";
++++fsw.EnableRaisingEvents+=+true;
++++fsw.Changed+%2B=+(s,e)+=>+wh.Set();

++++var+fs+=+new+FileStream("file-to-read",+FileMode.Open,+FileAccess.Read,+FileShare.ReadWrite);
++++using+(var+sr+=+new+StreamReader(fs))
++++{
++++++++var+s+=+"";
++++++++while+(true)
++++++++{
++++++++++++s+=+sr.ReadLine();
++++++++++++if+(s+!=+null)
++++++++++++++++Console.WriteLine(s);
++++++++++++else
++++++++++++++++wh.WaitOne(1000);
++++++++}
++++}

++++wh.Close();|code-block|syntax|javascript|1135313|在这里，主读周期停止等待传入的数据，FileSystemWatcher只是用来唤醒主读周期。|1135314|entityMap^0|2|H|0|0|I|H|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

More natural approach of using <code>FileSystemWatcher</code>:

<pre><code> var wh = new AutoResetEvent(false);
 var fsw = new FileSystemWatcher(".");
 fsw.Filter = "file-to-read";
 fsw.EnableRaisingEvents = true;
 fsw.Changed += (s,e) =&gt; wh.Set();

 var fs = new FileStream("file-to-read", FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
 using (var sr = new StreamReader(fs))
 {
 var s = "";
 while (true)
 {
 s = sr.ReadLine();
 if (s != null)
 Console.WriteLine(s);
 else
 wh.WaitOne(1000);
 }
 }

 wh.Close();
</code></pre>

Here the main reading cycle stops to wait for incoming data and <code>FileSystemWatcher</code> is used just to awake the main reading cycle.

blocks|key|1135344|text|要连续监控文件的尾部，您只需记住文件之前的长度。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1135345|public+static+void+MonitorTailOfFile(string+filePath)
{
++++var+initialFileSize+=+new+FileInfo(filePath).Length;
++++var+lastReadLength+=+initialFileSize+-+1024;
++++if+(lastReadLength+<+0)+lastReadLength+=+0;

++++while+(true)
++++{
++++++++try
++++++++{
++++++++++++var+fileSize+=+new+FileInfo(filePath).Length;
++++++++++++if+(fileSize+>+lastReadLength)
++++++++++++{
++++++++++++++++using+(var+fs+=+new+FileStream(filePath,+FileMode.Open,+FileAccess.Read,+FileShare.ReadWrite))
++++++++++++++++{
++++++++++++++++++++fs.Seek(lastReadLength,+SeekOrigin.Begin);
++++++++++++++++++++var+buffer+=+new+byte[1024];

++++++++++++++++++++while+(true)
++++++++++++++++++++{
++++++++++++++++++++++++var+bytesRead+=+fs.Read(buffer,+0,+buffer.Length);
++++++++++++++++++++++++lastReadLength+%2B=+bytesRead;

++++++++++++++++++++++++if+(bytesRead+==+0)
++++++++++++++++++++++++++++break;

++++++++++++++++++++++++var+text+=+ASCIIEncoding.ASCII.GetString(buffer,+0,+bytesRead);

++++++++++++++++++++++++Console.Write(text);
++++++++++++++++++++}
++++++++++++++++}
++++++++++++}
++++++++}
++++++++catch+{+}

++++++++Thread.Sleep(1000);
++++}
}|code-block|syntax|javascript|1135346|我不得不使用ASCIIEncoding，因为这段代码不够智能，无法在缓冲区边界上处理可变字符长度的UTF8。|1135347|备注:您可以将Thread.Sleep部件更改为不同的计时，也可以将其与文件守护程序和阻塞模式监视器相链接。输入/等待/脉冲。对我来说，计时器就足够了，如果文件没有变化，它最多只能每秒检查一次文件长度。|1135348|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

To continuously monitor the tail of the file, you just need to remember the length of the file before.

<pre><code>public static void MonitorTailOfFile(string filePath)
{
 var initialFileSize = new FileInfo(filePath).Length;
 var lastReadLength = initialFileSize - 1024;
 if (lastReadLength &lt; 0) lastReadLength = 0;

 while (true)
 {
 try
 {
 var fileSize = new FileInfo(filePath).Length;
 if (fileSize &gt; lastReadLength)
 {
 using (var fs = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
 {
 fs.Seek(lastReadLength, SeekOrigin.Begin);
 var buffer = new byte[1024];

 while (true)
 {
 var bytesRead = fs.Read(buffer, 0, buffer.Length);
 lastReadLength += bytesRead;

 if (bytesRead == 0)
 break;

 var text = ASCIIEncoding.ASCII.GetString(buffer, 0, bytesRead);

 Console.Write(text);
 }
 }
 }
 }
 catch { }

 Thread.Sleep(1000);
 }
}
</code></pre>

I had to use ASCIIEncoding, because this code isn't smart enough to cater for variable character lengths of UTF8 on buffer boundaries.

Note: You can change the Thread.Sleep part to be different timings, and you can also link it with a filewatcher and blocking pattern - Monitor.Enter/Wait/Pulse. For me the timer is enough, and at most it only checks the file length every second, if the file hasn't changed.

blocks|key|920837|text|这是我的解决方案|type|unstyled|depth|inlineStyleRanges|entityRanges|data|920838|++++static+IEnumerable<string>+TailFrom(string+file)
++++{
++++++++using+(var+reader+=+File.OpenText(file))
++++++++{
++++++++++++while+(true)+
++++++++++++{
++++++++++++++++string+line+=+reader.ReadLine();
++++++++++++++++if+(reader.BaseStream.Length+<+reader.BaseStream.Position)+
++++++++++++++++++++reader.BaseStream.Seek(0,+SeekOrigin.Begin);

++++++++++++++++if+(line+!=+null)+yield+return+line;
++++++++++++++++else+Thread.Sleep(500);
++++++++++++}
++++++++}
++++}|code-block|syntax|javascript|920839|因此，在您的代码中，您可以这样做|920840|++++foreach+(string+line+in+TailFrom(file))+
++++{
++++++++Console.WriteLine($"line+read=+{line}");++++++++++++
++++}|920841|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

This is my solution

<pre><code> static IEnumerable&lt;string&gt; TailFrom(string file)
 {
 using (var reader = File.OpenText(file))
 {
 while (true) 
 {
 string line = reader.ReadLine();
 if (reader.BaseStream.Length &lt; reader.BaseStream.Position) 
 reader.BaseStream.Seek(0, SeekOrigin.Begin);

 if (line != null) yield return line;
 else Thread.Sleep(500);
 }
 }
 }
</code></pre>

so, in your code you can do

<pre><code> foreach (string line in TailFrom(file)) 
 {
 Console.WriteLine($"line read= {line}"); 
 }
</code></pre>

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?

c# continuously read file

日志文件

文件系统

我想像GNU tail一样用"-f“参数连续读取文件。我需要它来实时读取日志文件。什么才是正确的方法呢？

问c#连续读取文件
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