Binaryworld - Redirect command line output to textbox using CreatePipe API ... [ VB -> Thread-Process ]

This example illustrates a Visual Basic application starting another process with the purpose of redirecting that process's standard IO handles. The Visual Basic application redirects the created process's standard output handle to an anonymous pipe, then proceeds to read the output through the pipe. This sample just redirects STDOUT of the new process. To redirect other handles (STDIN and STDERR), create a pipe for each handle for which redirection is desired. The Visual Basic application would read from the read ends of the pipes for the redirected STDOUT and STDERR. If STDIN redirection was desired, the Visual Basic application would write to the write end of the appropriate pipe. An example follows:

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'A pipe for redirection of STDOUT
CreatePipe(hReadPipe1, hWritePipe1, sa, 0)

'A pipe for redirection of STDERR
CreatePipe(hReadPipe2, hWritePipe2, sa, 0)

'A pipe for redirection of STDIN
CreatePipe(hReadPipe3, hWritePipe3, sa, 0)

'Preparing to start the process with redirected handles
start.hStdOutput = hWritePipe1
start.hStdError = hWritePipe2
start.hStdInput = hReadPipe3

'Reading output from the started process's STDOUT
ReadFile(hReadPipe1, mybuff1, 100, bytesread, ByVal 0&)

'Reading output from the started process's STDERR
ReadFile(hReadPipe2, mybuff2, 100, bytesread, ByVal 0&)

'Writing to the started process's STDIN
WriteFile(hWritePipe3, mybuff3, 100, byteswritten, ByVal 0&)

Step-By-Step Example

- Create a standard exe project
- Add 2 textbox controls and one command button control
- Set Multiline=True and Scrollbar=Verticle for Text2
- Add the following code in form1

Click here to copy the following block

Option Explicit
Private Declare Function CreatePipe Lib "kernel32" ( _
    phReadPipe As Long, _
    phWritePipe As Long, _
    lpPipeAttributes As SECURITY_ATTRIBUTES, _
    ByVal nSize As Long) As Long

Private Declare Sub GetStartupInfo Lib "kernel32" Alias "GetStartupInfoA" ( _
    lpStartupInfo As STARTUPINFO)

Private Declare Function CreateProcess Lib "kernel32" Alias "CreateProcessA" ( _
    ByVal lpApplicationName As String, _
    ByVal lpCommandLine As String, _
    lpProcessAttributes As Any, _
    lpThreadAttributes As Any, _
    ByVal bInheritHandles As Long, _
    ByVal dwCreationFlags As Long, _
    lpEnvironment As Any, _
    ByVal lpCurrentDriectory As String, _
    lpStartupInfo As STARTUPINFO, _
    lpProcessInformation As PROCESS_INFORMATION) As Long

Private Declare Function SetWindowText Lib "user32" Alias "SetWindowTextA" ( _
    ByVal hwnd As Long, _
    ByVal lpString As String) As Long

Private Declare Function ReadFile Lib "kernel32" ( _
    ByVal hFile As Long, _
    lpBuffer As Any, _
    ByVal nNumberOfBytesToRead As Long, _
    lpNumberOfBytesRead As Long, _
    lpOverlapped As Any) As Long

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" ( _
    ByVal hwnd As Long, _
    ByVal wMsg As Long, _
    ByVal wParam As Long, _
    lParam As Any) As Long

Private Declare Function CloseHandle Lib "kernel32" ( _
    ByVal hObject As Long) As Long

Private Type SECURITY_ATTRIBUTES
  nLength As Long
  lpSecurityDescriptor As Long
  bInheritHandle As Long
End Type

Private Type PROCESS_INFORMATION
  hProcess As Long
  hThread As Long
  dwProcessId As Long
  dwThreadId As Long
End Type

Private Type STARTUPINFO
  cb As Long
  lpReserved As Long
  lpDesktop As Long
  lpTitle As Long
  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 Byte
  hStdInput As Long
  hStdOutput As Long
  hStdError As Long
End Type

Private Type OVERLAPPED
  ternal As Long
  ternalHigh As Long
  offset As Long
  OffsetHigh As Long
  hEvent As Long
End Type

Private Const STARTF_USESHOWWINDOW = &H1
Private Const STARTF_USESTDHANDLES = &H100
Private Const SW_HIDE = 0
Private Const EM_SETSEL = &HB1
Private Const EM_REPLACESEL = &HC2

Private Sub Command1_Click()
  Command1.Enabled = False
  Redirect Text1.Text, Text2
  Command1.Enabled = True
End Sub
Private Sub Form_Load()
  '//Note: Some DOS command won't work (i.e dir, copy, del ... etc)
  Command1.Caption = "Run Command"
  'Text1.Text = "ping 127.0.0.1"
  'Text1.Text = "ipconfig /all"
  Text1.Text = "cmd /C " & "dir /b c:\"         '//Display only files
  Text2.Font.Name = "Terminal"
End Sub
Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
  If Command1.Enabled = False Then Cancel = True
End Sub

Sub Redirect(cmdLine As String, objTarget As Object)
  Dim i%, t$
  Dim pa As SECURITY_ATTRIBUTES
  Dim pra As SECURITY_ATTRIBUTES
  Dim tra As SECURITY_ATTRIBUTES
  Dim pi As PROCESS_INFORMATION
  Dim sui As STARTUPINFO
  Dim hRead As Long
  Dim hWrite As Long
  Dim bRead As Long
  Dim lpBuffer(1024) As Byte
  pa.nLength = Len(pa)
  pa.lpSecurityDescriptor = 0
  pa.bInheritHandle = True

  pra.nLength = Len(pra)
  tra.nLength = Len(tra)

  If CreatePipe(hRead, hWrite, pa, 0) <> 0 Then
    sui.cb = Len(sui)
    GetStartupInfo sui
    sui.hStdOutput = hWrite
    sui.hStdError = hWrite
    sui.dwFlags = STARTF_USESHOWWINDOW Or STARTF_USESTDHANDLES
    sui.wShowWindow = SW_HIDE

    If CreateProcess(vbNullString, cmdLine, pra, tra, True, 0, Null, vbNullString, sui, pi) <> 0 Then
      SetWindowText objTarget.hwnd, ""
      Do
        Erase lpBuffer()
        If ReadFile(hRead, lpBuffer(0), 1023, bRead, ByVal 0&) Then
          SendMessage objTarget.hwnd, EM_SETSEL, -1, 0
          SendMessage objTarget.hwnd, EM_REPLACESEL, False, lpBuffer(0)
          DoEvents
        Else
          Exit Do
        End If
        CloseHandle hWrite
      Loop
      CloseHandle hRead
    End If
  End If
End Sub