中财网足球培训内容:VB - 让Shell具有Wait功能
来源：百度文库 编辑：中财网 时间：2024/04/28 00:49:35
在 VB 中，常以 Shell 指令来执行外部程序，其传回值是PID，然而它在 Create 外部 Process 后，立刻就会回到下一行代码，无法做到等待该 Process 结束时，才执行下一行代码，或者说，无法得知该 Process 是否已结束，因此我们需借助 API 函数来完成。
现举例说明 "WaitForShell" 在控制 Shell 指令中的作用：
****************************************************************************************************************
Option Explicit
Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
Private Declare Function OpenProcess Lib "kernel32" (ByVal dwDesiredAccess As Long, _
ByVal bInheritHandle As Long, _
ByVal dwProcessId As Long) As Long
Private Declare Function GetExitCodeProcess Lib "kernel32" (ByVal hProcess As Long, _
lpExitCode As Long) As Long
Const PROCESS_QUERY_INFORMATION = &H400
Const STILL_ALIVE = &H103
'-------------------｛WaitForShell｝------------------
'让 Shell 所 Create 的 Process 具有 Wait 功能
'-----------------------------------------------------------
Sub WaitForShell(ByVal PID As Long)
Dim hProcess As Long, ExitCode As Long
Dim isDone As Boolean
hProcess = OpenProcess(PROCESS_QUERY_INFORMATION, 0, PID)
isDone = False
Do
Call GetExitCodeProcess(hProcess, ExitCode)
DoEvents
Loop While ExitCode = STILL_ALIVE
Call CloseHandle(hProcess)
isDone = True
End Sub
'调用示例：
Private Sub Command1_Click()
Dim sPid As Long
Dim ReadLine As String, Rtn As String
'╱＊调用 cmd 执行 vol 指令：用以显示磁盘卷标和序列号，并写入 d 盘目录下的 "Disk.txt" 文件＊╱
sPid = Shell("cmd /c vol d:>d:\Disk.txt", vbHide)
'╱＊若注释掉下面一句，会出现“文件未找到！”的错误，因为文件尚未创建好就去读必然出错。＊╱
Call WaitForShell(sPid)
'╱＊尝试读取 "d:\Disk.txt"里的内容＊╱
Open "d:\Disk.txt" For Input As #1
Do While Not EOF(1)
Line Input #1, ReadLine
Rtn = Rtn & ReadLine
Loop
Close #1
MsgBox Rtn
End Sub