Mirroring console output to a file

In a C# console application, is there a smart way to have console output mirrored to a text file?

Currently I am just passing the same string to both Console.WriteLine and InstanceOfStreamWriter.WriteLine in a log method.

This may be some kind of more work, but I would go the other way round.

Instantiate a TraceListener for the console and one for the log file; thereafter use Trace.Write statements in your code instead of Console.Write. It becomes easier afterwards to remove the log, or the console output, or to attach another logging mechanism.

static void Main(string[] args)
{
    Trace.Listeners.Clear();

    TextWriterTraceListener twtl = new TextWriterTraceListener(Path.Combine(Path.GetTempPath(), AppDomain.CurrentDomain.FriendlyName));
    twtl.Name = "TextLogger";
    twtl.TraceOutputOptions = TraceOptions.ThreadId | TraceOptions.DateTime;

    ConsoleTraceListener ctl = new ConsoleTraceListener(false);
    ctl.TraceOutputOptions = TraceOptions.DateTime;

    Trace.Listeners.Add(twtl);
    Trace.Listeners.Add(ctl);
    Trace.AutoFlush = true;

    Trace.WriteLine("The first line to be in the logfile and on the console.");
}

As far as I can recall, you can define the listeners in the application configuration making it possible to activate or deactivate the logging without touching the build.

This is a simple class which subclasses TextWriter to allow redirection of the input to both a file and the console.

Use it like this

  using (var cc = new ConsoleCopy("mylogfile.txt"))
  {
    Console.WriteLine("testing 1-2-3");
    Console.WriteLine("testing 4-5-6");
    Console.ReadKey();
  }

Here is the class:

class ConsoleCopy : IDisposable
{

  FileStream fileStream;
  StreamWriter fileWriter;
  TextWriter doubleWriter;
  TextWriter oldOut;

  class DoubleWriter : TextWriter
  {

    TextWriter one;
    TextWriter two;

    public DoubleWriter(TextWriter one, TextWriter two)
    {
      this.one = one;
      this.two = two;
    }

    public override Encoding Encoding
    {
      get { return one.Encoding; }
    }

    public override void Flush()
    {
      one.Flush();
      two.Flush();
    }

    public override void Write(char value)
    {
      one.Write(value);
      two.Write(value);
    }

  }

  public ConsoleCopy(string path)
  {
    oldOut = Console.Out;

    try
    {
      fileStream = File.Create(path);

      fileWriter = new StreamWriter(fileStream);
      fileWriter.AutoFlush = true;

      doubleWriter = new DoubleWriter(fileWriter, oldOut);
    }
    catch (Exception e)
    {
      Console.WriteLine("Cannot open file for writing");
      Console.WriteLine(e.Message);
      return;
    }
    Console.SetOut(doubleWriter);
  }

  public void Dispose()
  {
    Console.SetOut(oldOut);
    if (fileWriter != null)
    {
      fileWriter.Flush();
      fileWriter.Close();
      fileWriter = null;
    }
    if (fileStream != null)
    {
      fileStream.Close();
      fileStream = null;
    }
  }

}

Check out log4net. With log4net you can set up console and file appenders that will can output log messages to both places with a single log statement.

Can't you just redirect the output to a file, using the > command?

c:\>Console.exe > c:/temp/output.txt

If you need to mirror, you can try find a win32 version of tee that splits the output to a file.

See https://superuser.com/questions/74127/tee-for-windows to run tee from PowerShell

You could subclass the TextWriter class, and then assign its instance to the Console.Out using the Console.SetOut method - which in particular does the same thing as passing the same string to both methods in the log method.

Another way might declaring your own Console class and use the using statement to distinguish between the classes:

using Console = My.Very.Own.Little.Console;

To access the standard console you'd then need:

global::Console.Whatever