c output in vb

[gokul]

how do i run a c pgm in dos prompt using vb and view the output in a vb text box or any other feature of vb ?
plz advise

[riis]

I don't know how to show output realtime in a textbox. (Maybe a real C guru will know how to do it.) I couldn't determine from your question if you meant that.
However, I know a way to show the contents in a textbox after execution.

I found this example to run DOS programs somewhere on the net (vbexplorer I think). It seems to be better than the Shell command, but I forgot why. At least this works well for me

Private Type STARTUPINFO
  cb As Long
  lpReserved As String
  lpDesktop As String
  lpTitle As String
  dwX As Long
  dwY As Long
  dwXSize As Long
  dwYSize As Long
  dwXCountChars As Long
  dwYCountChars As Long
  dwFillAttribute As Long
  dwFlags As Long
  wShowWindow As Integer
  cbReserved2 As Integer
  lpReserved2 As Long
  hStdInput As Long
  hStdOutput As Long
  hStdError As Long
  End Type
 
Private Type PROCESS_INFORMATION
  hProcess As Long
  hThread As Long
  dwProcessID As Long
  dwThreadID As Long
End Type
 
Private Declare Function WaitForSingleObject Lib "kernel32" (ByVal _
  hHandle As Long, ByVal dwMilliseconds As Long) As Long
 
Private Declare Function CreateProcessA Lib "kernel32" (ByVal _
  lpApplicationName As String, ByVal lpCommandLine As String, ByVal _
  lpProcessAttributes As Long, ByVal lpThreadAttributes As Long, _
  ByVal bInheritHandles As Long, ByVal dwCreationFlags As Long, _
  ByVal lpEnvironment As Long, ByVal lpCurrentDirectory As String, _
  lpStartupInfo As STARTUPINFO, lpProcessInformation As _
  PROCESS_INFORMATION) As Long
 
Private Declare Function CloseHandle Lib "kernel32" _
  (ByVal hObject As Long) As Long
 
Private Declare Function GetExitCodeProcess Lib "kernel32" _
 (ByVal hProcess As Long, lpExitCode As Long) As Long
 
Private Const NORMAL_PRIORITY_CLASS = &H20&
Private Const INFINITE = -1&
 
Public Function ExecCmd(cmdline As String) As Long
  Dim proc As PROCESS_INFORMATION
  Dim start As STARTUPINFO
  Dim ret As Long
  
  ' Initialize the STARTUPINFO structure:
  start.cb = Len(start)
  
  ' Start the shelled application:
  ret = CreateProcessA(vbNullString, cmdline$, 0&, 0&, 1&, _
     NORMAL_PRIORITY_CLASS, 0&, vbNullString, start, proc)
  
  ' Wait for the shelled application to finish:
  ret = WaitForSingleObject(proc.hProcess, INFINITE)
  Call GetExitCodeProcess(proc.hProcess, ret)
  Call CloseHandle(proc.hThread)
  Call CloseHandle(proc.hProcess)
  ExecCmd = ret
  
End Function

In your program, create a variable as long. Name it something like retVal, since it will hold the return value of your program.
Create another variable as string, like sCommand. This will be your command string. In your command string, direct the output of your C app to a file: "c:\dir\blah.exe >output.txt".

Call your C app like this:
retVal = ExecCmd(sCommand)

If retVal = 0, then execution has completed successfully, and you can go further with your code. If retVal <> 0, then something has happened, and the C program produced an error code.

In your VB app, read the contents of output.txt and show it in your textbox.

I'm not 100% sure if this will work, since I haven't tested it with redirection output to a file and then to a textbox, if your program is being called from VB.

[riis]

Maybe I know a workaround to show your C app's output realtime, although it's being faked a little.

Your C app could write some texts to temporary files, which can be read by your VB app. You could use the GetTickCount API to check for the existance of new files.

This can be somewhat tricky, since a file might still be open when you're trying to read it in VB, but sound error handling surely will deal with it

[JoshT]

Private Type STARTUPINFO
  cb As Long
  lpReserved As String
  lpDesktop As String
  lpTitle As String
  dwX As Long
  dwY As Long
  dwXSize As Long
  dwYSize As Long
  dwXCountChars As Long
  dwYCountChars As Long
  dwFillAttribute As Long
  dwFlags As Long
  wShowWindow As Integer
  cbReserved2 As Integer
  lpReserved2 As Long
  [b]hStdInput As Long
  hStdOutput As Long
  hStdError As Long[/b]
  End Type

The members I made bold can be pass handles to Pipes if you set the correct dwFlags value, enabling you to redirect Standard IO to a Pipe your VB app can read.

[riis]

Cool, I didn't know that. But how can VB read from that pipe. Is there another API call for that? Or should they refer to the hwnd property (or a different one) of your textbox?

[riis]

Never mind, I already found an example