如何重新定义clog到三通到原始的clog和日志文件？ [英] How to redefine clog to tee to original clog and a log file?

问题描述

我在这里看到一个有用的开始：

http://www.cs.technion.ac.il/~imaman/programs/teestream.html

并且它工作伟大的做一个新的流去阻塞和日志文件。

但是，如果我试图重新定义clog是新的流，它不工作，因为新的流具有与clog相同的rdbuf（），所以以下没有效果：

  clog.rdbuf（myTee。 rdbuf（））; 
  

那么如何修改tee类以具有自己的rdbuf

-William

解决方案

如果你真的想继续使用std :: clog作为发球区域，而不是将输出发送到不同的流，你需要降低一个级别：而不是派生自ostream，派生从streambuf。那么你可以这样做：

  fstream logFile（...） 
 TeeBuf tbuf（logFile.rdbuf（），clog.rdbuf（））; 
 clog.rdbuf（& tbuf）; 
  

有关如何派生自己的streambuf类的更多信息，请参阅此处。

I saw a useful start here:

http://www.cs.technion.ac.il/~imaman/programs/teestream.html

And it works great to make a new stream which goes to both clog and a log file.

However, if I try to redefine clog to be the new stream it does not work because the new stream has the same rdbuf() as clog so the following has no effect:

clog.rdbuf(myTee.rdbuf());

So how can I modify the tee class to have its own rdbuf() which can then be the target of clog?

Thanks.

-William

解决方案

If you really want to keep using std::clog for the tee instead of sending output to a different stream, you need to work one level lower: Instead of deriving from ostream, derive from streambuf. Then you can do this:

fstream logFile(...);
TeeBuf tbuf(logFile.rdbuf(), clog.rdbuf());
clog.rdbuf(&tbuf);

For more information on how to derive your own streambuf class, see here.

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