SAMPLE: RunWait.exe - DLL Provides Synchronous Spawn Function

ID: Q105116

The information in this article applies to:

Microsoft Windows Software Development Kit (SDK) for Windows versions 3.0, 3.1

SUMMARY

The sample RunWait.exe demonstrates how to use TOOLHELP.DLL to provide a dynamic-link library (DLL) function that spawns applications and waits for their termination before returning from the function call. The sample is compatible with Visual Basic (VB) and Windows 3.0. The sample loads a hidden task at DLL startup time to own the Toolhelp callback.

MORE INFORMATION

The following file is available for download from the Microsoft Software Library:

 ~ RunWait.exe (size: 23229 bytes)

For more information about downloading files from the Microsoft Software Library, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q119591
   TITLE     : How to Obtain Microsoft Support Files from Online Services

The following is the VB function declaration (this must be on a single line in VB):

Declare Function SpawnAndWait& Lib "RUNLIB.DLL" (ByVal parenthwnd%,

ByVal lpszOp$, ByVal lpszFile$, ByVal lpszParams$, ByVal lpszDir$, ByVal nShow%)

DWORD SpawnAndWait(hwnd, lpszOp, lpszFile, lpszParams, lpszDir, fsShowCmd)

HWND   hwnd        /* Handle of parent window                          */
LPCSTR lpszOp      /* Address of string for operation to perform       */
LPCSTR lpszFile    /* Address of string for filename                   */

LPCSTR lpszParams /* Address of string for executable-file parameters */

LPSCTR lpszDir     /* Address of string for default directory          */
int    fsCmdShow   /* Whether file is shown when opened                */

The SpawnAndWait function executes and waits for termination of the specified application or associated file.

Parameter Description

hwnd       Identifies the parent window. This window receives any message
           boxes an application produces (for example, for error
           reporting).

lpszOp     Points to a null-terminated string specifying the operation to
           perform. This string can be "open" or "print". If this parameter
           is NULL, "open" is the default value.

lpszFile   Points to a null-terminated string specifying the file to
           open.

lpszParams Points to a null-terminated string specifying parameters

           NULL; "open" is the default value. Passed to the application
           when the lpszFile parameter specifies an executable file. If
           lpszFile points to a string specifying a document file, this
           parameter is NULL.

lpszDir    Points to a null-terminated string specifying the default
           directory.

fsShowCmd Specifies whether the application window is to be shown when

           the application is opened. See ShowWindow for valid values.

Returns

HIWORD == hInstance of started application. Values less than 32 are errors

          returned from ShellExecute. 0xFFFF is a general error.

LOWORD == Return code of spawned application. 0xFFFF is a general error.

Comments

The file specified by the lpszFile parameter can be a document file or an executable file. If it is a document file, this function opens or prints it, depending on the value of the lpszOp parameter. If it is an executable file, this function opens it, even if the string "print" is pointed to by lpszOp.

WARNING: This function will not wait on applications such as Word and Excel that respond to the DDE broadcast made by ShellExecute or the second instance of multiple data applications.

WARNING: This function supports only one block at a time per task. Calling tasks should not call this function when it has a prior pending SpawnAndWait call.

Sample Code

DWORD SpawnAndWaitIndirect(lpSpawnWait)

LPSPAWNWAIT lpSpawnWait /* Far reference to SPAWNWAIT structure

typedef struct tagSPAWNWAIT {

   HWND   hwnd;
   LPCSTR lpszOp;
   LPCSTR lpszFile;
   LPCSTR lpszParams;
   LPCSTR lpszDir;
   int    fsShowCmd;
   LPMSGPROC lpmsgproc;

} SPAWNWAIT;

Member       Description

hwnd         Handle of parent window
lpszOp       Address of string for operation to perform
lpszFile     Address of string for filename
lpszParams   Address of string for executable-file parameters
lpszDir      Address of string for default directory
fsShowCmd    Whether file is shown when opened
lpmsgproc    Address of application provided MessagePump (must load
             DS on entry)

void CALLBACK MessagePump(lpmsg)

LPSMG lpsg   /* Long pointer to MSG to process

Message Proc is a place holder for an application-provided callback function (which must load DS on entry) that will process messages retrieved in RunLib's PeekMessage loop. It allows the calling application to do modeless dialog box and accelerator message processing.

lpmsgproc should be set to NULL if it is not used. RunLib will do a default TranslateMessage/DispatchMessage instead.

The following is an example of a message processing function for a MDI application:

void CALLBACK MyMessagePump(LPMSG lpmsg)

{

   if(!TranslateMDISysAccel(hClient, lpsmg) &&
      !TranslateAccelerator(hFram, hAccel, lpsmg))
      {
         TranslateMessage(lpsmg);
         DispatchMessage(lpmsg);
      }

}

Returns

HIWORD == hInstance of started application. Values less than 32 are errors

          returned from ShellExecute. 0xFFFF is a general error.

LOWORD == Return code of spawned application. 0xFFFF is a general

          error.

Comments

WARNING: This function will not wait on applications such as Word and Excel that respond to the DDE broadcast made by ShellExecute or the second instance of multiple data applications.

WARNING: This function supports only one block at a time per task. Calling tasks should not call this function when it has a prior pending SpawnAndWait call.

Additional query words: Keywords : kbfile kbsample kb16bitonly

Last Reviewed: December 10, 1998