by Darrell Sparti, MCSD (2 Submissions)
Category: Windows API Call/Explanation
Compatability: Visual Basic 3.0
Difficulty: Unknown Difficulty
Date Added: Wed 3rd February 2021
Rating: 
(17 Votes)
Unlike the Shell command in VB which launches an application
asynchronous, this will launch the program synchronous.
What that means is that the shell execute command will launch
an application but not wait for it to execute before processing
the next line of code. This code will launch a program then
wait until the executable has terminated before executing the
next line of code.
Inputs
INPUT: The executables full path and name.
Code Returns
RETURN: True upon termination if successful, false if not.
API DeclarationsPrivate Const INFINITE = &HFFFFFFFF
Private Const NORMAL_PRIORITY_CLASS = &H20
Private Const WAIT_TIMEOUT = &H102&
'
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 CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
'
Private Declare Function WaitForInputIdle Lib "user32" (ByVal hProcess As Long, ByVal dwMilliseconds As Long) As Long
'
Private Declare Function CreateProcessByNum Lib "kernel32" Alias "CreateProcessA" _
(ByVal lpApplicationName As String, ByVal lpCommandLine As String, ByVal lpProcessAttributes _
As Long, ByVal lpThreadAttributes As Long, ByVal bInheritHandles As Long, ByVal dwCreationFlags _
As Long, lpEnvironment As Any, ByVal lpCurrentDirectory As String, lpStartupInfo As _
STARTUPINFO, lpProcessInformation As PROCESS_INFORMATION) As Long
'
Private Declare Function WaitForSingleObject Lib "kernel32" (ByVal hHandle As Long, ByVal dwMilliseconds As Long) As Long
'
VBcodersOption Explicit
'
'Unlike the Shell command in VB which launches an application
'asynchronous, this will launch the program synchronous.
'What that means is that the shell execute command will launch
'an application but not wait for it to execute before processing
'the next line of code. This code will launch a program then
'wait until the executable has terminated before executing the
'next line of code. Works great for launching DOS exe's such
'as batch files, reindexing old databases, and other executables
'which must perform their task before your code continues.
'Some versions don't work in Windows NT because of the added
'security but this version does work in Windows NT.
'I realize there are more elegant and sophisticated ways to do
'the same thing but this one works fine for what I needed in a
'professional application I was working on. I must credit Dan
'Appleman's Programmer's Guide To The Win32 API for this code.
'I also strongly suggest that anyone interested in understanding
'more about these kind of techniques, read his book. In fact,
'I recommend all of Dan Appleman's books when you are ready to
'go from novice to professional programmer.
'I appreciate your comments but please do your homework first!
Public Function LaunchAppSynchronous(strExecutablePathAndName As String) As Boolean
'Launches an executable by starting it's process
'then waits for the execution to complete.
'INPUT: The executables full path and name.
'RETURN: True upon termination if successful, false if not.
Dim lngResponse As Long
Dim typStartUpInfo As STARTUPINFO
Dim typProcessInfo As PROCESS_INFORMATION
LaunchAppSynchronous = False
With typStartUpInfo
.cb = Len(typStartUpInfo)
.lpReserved = vbNullString
.lpDesktop = vbNullString
.lpTitle = vbNullString
.dwFlags = 0
End With
'Launch the application by creating a new process
lngResponse = CreateProcessByNum(strExecutablePathAndName, vbNullString, 0, 0, True, NORMAL_PRIORITY_CLASS, ByVal 0&, vbNullString, typStartUpInfo, typProcessInfo)
If lngResponse Then
'Wait for the application to terminate before moving on
Call WaitForTermination(typProcessInfo)
LaunchAppSynchronous = True
Else
LaunchAppSynchronous = False
End If
End Function
Private Sub WaitForTermination(typProcessInfo As PROCESS_INFORMATION)
'This wait routine allows other application events
'to be processed while waiting for the process to
'complete.
Dim lngResponse As Long
'Let the process initialize
Call WaitForInputIdle(typProcessInfo.hProcess, INFINITE)
'We don't need the thread handle so get rid of it
Call CloseHandle(typProcessInfo.hThread)
'Wait for the application to end
Do
lngResponse = WaitForSingleObject(typProcessInfo.hProcess, 0)
If lngResponse <> WAIT_TIMEOUT Then
'No timeout, app is terminated
Exit Do
End If
DoEvents
Loop While True
'Kill the last handle of the process
Call CloseHandle(typProcessInfo.hProcess)
End Sub
