Console application. Console.Clear = IOException

  • Thread starter Thread starter Dinsdale
  • Start date Start date
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Dinsdale

I am writing a small console application that runs fine unless I am re-
directing the output to a file (i.e. c:\ > app.exe >>output.txt) . I
have determined that the issue is caused by the Console.Clear()
function. When piping to a file, the console.clear causes the
following error:

Unhandled Exception: System.IO.IOException: The handle is invalid.

at System.IO.IO__Error.WinIOError(Int32 errorCode, String
maybeFullPath)
at System.Console.Clear()
....

Is there any way to determine where my output is being directed so
that I can skip over the Console.Clear command if I am re-directing
stdOut?

The other side of the error is with input. I prompt the user at one or
two points but if the output is re-directed, I would like to simply
skip the prompt. Again, this would be possible if I can determine
where standard output is going.

Thanks!
Dinsdale
 
I am writing a small console application that runs fine unless I am re-
directing the output to a file (i.e. c:\ > app.exe >>output.txt) . I
have determined that the issue is caused by the Console.Clear()
function. When piping to a file, the console.clear causes the
following error:

Unhandled Exception: System.IO.IOException: The handle is invalid.

at System.IO.IO__Error.WinIOError(Int32 errorCode, String
maybeFullPath)
at System.Console.Clear()
...

Is there any way to determine where my output is being directed so
that I can skip over the Console.Clear command if I am re-directing
stdOut?

The other side of the error is with input. I prompt the user at one or
two points but if the output is re-directed, I would like to simply
skip the prompt. Again, this would be possible if I can determine
where standard output is going.

Thanks!
Dinsdale
Click to expand...

So did nobody answer this because I am stupid and totally missed
something obvious? Seriously, hints anyone???
 
I am writing a small console application that runs fine unless I am re-
directing the output to a file (i.e. c:\ > app.exe >>output.txt) . I
have determined that the issue is caused by the Console.Clear()
function. When piping to a file, the console.clear causes the
following error:

Unhandled Exception: System.IO.IOException: The handle is invalid.

at System.IO.IO__Error.WinIOError(Int32 errorCode, String
maybeFullPath)
at System.Console.Clear()
...

Is there any way to determine where my output is being directed so
that I can skip over the Console.Clear command if I am re-directing
stdOut?

The other side of the error is with input. I prompt the user at one or
two points but if the output is re-directed, I would like to simply
skip the prompt. Again, this would be possible if I can determine
where standard output is going.

Thanks!
Dinsdale
Click to expand...

AFIK, there is no way to tell if you have been redirected. Sorry.
 
I am writing a small console application that runs fine unless I am re-
directing the output to a file (i.e. c:\ > app.exe >>output.txt) . I
have determined that the issue is caused by the Console.Clear()
function. When piping to a file, the console.clear causes the
following error:

Unhandled Exception: System.IO.IOException: The handle is invalid.

at System.IO.IO__Error.WinIOError(Int32 errorCode, String
maybeFullPath)
at System.Console.Clear()
...

Is there any way to determine where my output is being directed so
that I can skip over the Console.Clear command if I am re-directing
stdOut?

The other side of the error is with input. I prompt the user at one or
two points but if the output is re-directed, I would like to simply
skip the prompt. Again, this would be possible if I can determine
where standard output is going.

Thanks!
Dinsdale
Click to expand...

You can't do it directly from the framework. However, take a look at
http://msdn.microsoft.com/archive/default.asp?url=/archive/en-us/dnaraskdr/html/askgui07152003.asp
for information detecting redirection. Personally, I would wrap my
Console.Clear() function inside a small sub as follows:

public Sub ClearConsole()
static failed as boolean = false
if failed then exit sub

try
system.Console.Clear()
catch
failed = true
end try
end sub

Mike.
 
You can't do it directly from the framework.  However, take a look athttp://msdn.microsoft.com/archive/default.asp?url=/archive/en-us/dnar...
Click to expand...


Hey, Michael - good find. I wasn't aware of the PeekConsoleInput
trick... This may actually be what the OP needs, because he also
wants to not display the prompt....
 
Hey, Michael - good find. I wasn't aware of the PeekConsoleInput
trick... This may actually be what the OP needs, because he also
wants to not display the prompt....
Click to expand...

Thanks Michael, this is the type of info I was looking for. I kind of
assumed I would have to delve into some win32 / platform sdk stuff.
Another good article can be found here: http://msdn2.microsoft.com/en-us/library/ms682075.aspx
I found this while research the Dr. Gui article you referenced. Also a
reference file here: http://msdn2.microsoft.com/en-us/library/ms682073(VS.85).aspx.
I'll try to remember to post an answer if I find one as the Dr.Gui
example deals with input, not output...

Cheers,
Dinsdale
 
Thanks Michael, this is the type of info I was looking for. I kind of
assumed I would have to delve into some win32 / platform sdk stuff.
Another good article can be found here:http://msdn2.microsoft.com/en-us/library/ms682075.aspx
I found this while research the Dr. Gui article you referenced. Also a
reference file here:http://msdn2.microsoft.com/en-us/library/ms682073(VS.85).aspx.
I'll try to remember to post an answer if I find one as the Dr.Gui
example deals with input, not output...

Cheers,
Dinsdale
Click to expand...

Okay, here's what I have so far:

I can use the GetStdHandle sdk call in VB.net to return the handle of
the current console window (code below). In the preliminary tests, I
find that the IntPtr returns 7 if the handle is pointing to the
console window, and a value other than 7 if it is pointing to a file
(i.e. 132, 128 etc). What I do not know for sure is if the console
window ALWAYS returns 7? This seems way too easy for the level of
effort I have had to invest in finding this solution... Can anyone
confirm or deny this (return value of 7, not my effot level. lol)?

Code:

Imports System
Imports System.Runtime.InteropServices

Module Module1

Sub Main()

Dim handle As IntPtr

handle = STDIO.GetStdHandle(STDIO.STD_OUTPUT_HANDLE)

If handle <> 7 Then
Console.WriteLine("This is a redirected console. Handle # " +
handle.ToString())
Else
Console.WriteLine("Not redirected")
Console.ReadLine()
End If

End Sub

End Module

Class STDIO
' see http://msdn2.microsoft.com/en-us/library/ms683231(VS.85).aspx
Public Const STD_OUTPUT_HANDLE As Long = (-11 And &HFFFFFFFFL)

<DllImport("Kernel32", SetLastError:=True)> _
Public Shared Function GetStdHandle(ByVal nStdHandle As
System.UInt32) _
As IntPtr
End Function

End Class


Cheers,
Dinsdale
 
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