Harnessing the Power of DOS

[kazar]

It's a fact - APIs have replaced many of the DOS Functions, and yet there are still people who consider dos a powerful tool, after all .net provides the ability to make console applications.

So, i created a simple way, without messing around with console opening and manipulation, of sending and recieving the results of DOS commands in VB6.

Sending a DOS Command:

Now for most vb programmers, sending a command to DOS is easy as pie. However, if you want to receive a command from DOS, you need to wait for the command to finish executing, right? So i use this code to send a command to DOS and wait for it to finish. Some of it can be found on MSDN btw.

Option Explicit
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 Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
   Private Type PROCESS_INFORMATION
      hProcess As Long
      hThread As Long
      dwProcessID As Long
      dwThreadID As Long
   End Type
Private Declare Function GetSystemDirectory Lib "kernel32" Alias "GetSystemDirectoryA" (ByVal lpBuffer As String, ByVal nSize As Long) As Long
   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$)
      Dim proc As PROCESS_INFORMATION
      Dim start As STARTUPINFO
 
      ' 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)
       DoEvents
        Dim sysbuffer As String
        Dim sysbuffersize As Long
         GetSystemDirectory sysbuffer, sysbuffersize
 
      ' 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
 
Function SendDOSCommand(command as string, destlog as string)
 
'i know that using bat files is a strange way to do it, but i find it works better
 
     Open "C:\Dosemu.bat" for output as #1
              Print #1, command + " > " + destlog
 
'the  > destlog part is the key to the whole thing, since it forces dos to copy it's results to the specifyed file
 
     Close
 
 
 ExecCmd ("C:\dosemu.bat")
'this line waits for the command to finish executing
Kill ("C:\dosemu.bat")
'and this gets rid of the temp bat file
 
End Function

So thats that for sending commands, now for retrieving them. In the code above, the dos results have been saved to a file, called destlog.

To get them back is simple. Just Read the File! Create a textbox and call it dosbox, with multiline enabled.

Sub getdosresults(doslog as string)
 
Open doslog For Input As #1
    On Error GoTo skipfile
        Do
        Input #1, buffer
        dosbox.Text = dosbox.Text + buffer + vbCrLf
     'this line gets each line from the file and adds a next line character
        Loop
        
skipfile:
Close
 
End Sub