How can I determine whether Console.Out has been redirected to a file?

Question

If my program is printing to the console, I perform word-wrapping in a certain way according to Console.WindowWidth by inserting newlines - and this works perfectly.

However if the output of the program is redirected to a file or another program I would like it to skip the word-wrapping. How can I detect when this is the case?

Console.WindowWidth returns the same number in both cases.

Bonus points if the solution can distinguish redirected Console.Out from redirected Console.Error.

Answer 1

.NET 4.5 adds Console.IsOutputRedirected and Console.IsErrorRedirected.

Answer 2

p/invoke GetFileType(GetStdHandle(STD_OUTPUT_HANDLE)), or call an innocuous console function like GetConsoleScreenBufferInfo to check for invalid handle error. If you want to know about standard error, use STD_ERROR_HANDLE. I believe you can even compare handles returned by GetStdHandle(STD_OUTPUT_HANDLE) and GetStdHandle(STD_ERROR_HANDLE) to detect stuff like 2>&1.

Answer 3

While this is a little shady and probably isn't guaranteed to work, you can try this:

bool isRedirected;

try
{
    isRedirected = Console.CursorVisible && false;
}
catch
{
    isRedirected = true;
}

Calling CursorVisible throws an exception when the console is redirected.

Answer 4

You need to use reflection - a bit grubby but the following will work:

static bool IsConsoleRedirected()
{
    var writer = Console.Out;
    if (writer == null || writer.GetType ().FullName != "System.IO.TextWriter+SyncTextWriter") return true;
    var fld = writer.GetType ().GetField ("_out", BindingFlags.Instance | BindingFlags.NonPublic);
    if (fld == null) return true;
    var streamWriter = fld.GetValue (writer) as StreamWriter;
    if (streamWriter == null) return true;
    return streamWriter.BaseStream.GetType ().FullName != "System.IO.__ConsoleStream";
}