In one of my programs I am using rundll32.exe url.dll,FileProtocolHandler c:\path\to\a.file to open files. I would like to handle errors in case this file could not be opened but I can't figure out how to find out if there was an error or not.
That's my code:
QProcess::startDetached( QString( "rundll32.exe url.dll,FileProtocolHandler " + p_target_path ) );
startDetached() now always returns true, because it's always succesfull in opening a process containing rundll32.exe. So how do I know if my file could be found/opened or not?
I tried errorlevel-things in a *.bat file for testing.
rundll32.exe url.dll,FileProtocolHandler c:\not_existing.exe >nul || echo Could not open file.
But there is nothing being echoed. I also tried to read the %ERRORLEVEL%, but even if the file is not existing the errorlevel remains 0.
Does anyone know a way to find out how to deal with this?
It seems to me that rundll32.exe is really not return an erorlevel. It you look at http://support.microsoft.com/kb/164787 you can see, that Rundll32 Interface has no defined way to return error.
VOID CALLBACK FileProtocolHandler (
__in HWND hwnd,
__in HINSTANCE ModuleHandle,
__in PCTSTR pszCmdLineBuffer,
__in INT nCmdShow
);
By the way you can call the function FileProtocolHandler exported by url.dll directly without starting rundll32.exe. As pszCmdLineBuffer you can give p_target_path. Nevertheless you will receive no error information.
UPDATED: By the way if you use rundll32.exe url.dll,FileProtocolHandler to open files only and not URLs than you can use ShellExecute or ShellExecuteEx instead with the verb "open" or NULL (see http://msdn.microsoft.com/en-us/library/bb776886.aspx). In the simplest case the code could looks like following
HINSTANCE hInst = ShellExecute (NULL, TEXT("open"), TEXT("c:\path\to\a.file"), NULL, NULL, 0);
You can test hInst for the errors (see Return Value in http://msdn.microsoft.com/en-us/library/bb762153.aspx)