Ejemplos usando el Api de windows para Visual basic

259 - WaitForSingleObject - Lanzar proceso y saber cuando termina

Ejemplo de la KB de Microsoft que usa las funciones del api WaitForSingleObject, CreateProcessA y GetExitCodeProcess

Descripción :

Este ejemplo de microsoft muestra como ejecutar mediante el Shell del sistema un proceso, y saber cuando el proceso lanzado se ha cerrado o finalizado, en este caso mostrando un mensaje

Código fuente en un formulario ( indicar el proceso que se va a abrir )

Option Explicit ' estructuras '''''''''''''''''' 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 ' Funciones Api '''''''''''''''''' 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 ejecutar_Comando(cmdline As String) Dim proc As PROCESS_INFORMATION Dim start As STARTUPINFO Dim ret As Long start.cb = Len(start) ret = CreateProcessA( _ vbNullString, _ cmdline$, _ 0&, 0&, 1&, _ NORMAL_PRIORITY_CLASS, _ 0&, vbNullString, _ start, proc) ret& = WaitForSingleObject(proc.hProcess, INFINITE) Call GetExitCodeProcess(proc.hProcess, ret&) Call CloseHandle(proc.hThread) Call CloseHandle(proc.hProcess) ejecutar_Comando = ret& End Function Sub Form_Click() Dim ret As Long Dim Proceso As String ' linea de comandos Proceso = "mspaint.exe" ret = ejecutar_Comando("mspaint.exe") MsgBox "El proceso :" & Proceso & " se ha cerrado", vbInformation End Sub Private Sub Form_Load() MsgBox "Hacer clic en el formulario", vbInformation End Sub

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