CreateProcess and CreatePipe to execute a process and return output as a string in VC++

Question

I am trying to use CreateProcess and CreatePipe to execute a process from within a Windows Forms C++/CLR application in Visual Studio 2010.

Answer 1

You are not making correct use of the ::ReadFile() function.

Read about it here: http://msdn.microsoft.com/en-us/library/ms891445.aspx

Basically, you want to fail with an error if the function ever does not return TRUE, and you want to keep looping until it yields a zero reDword.

Also, ::ReadFile() will not zero-terminate your data for you, so you have to do it yourself, like this: buf[reDword] = '\0'; (make sure your buf is 101 chars long before doing that.)

EDIT: Since I was asked to provide some example code, here it is, though I have not gone through the trouble of actually compiling it to make sure it works, so please beware of syntax errors, and generally consider it only as a rough pointer to the direction in which it should be done:

#define BUFFER_SIZE 100
string csoutput;
for( ;; )
{
    char buf[BUFFER_SIZE+1];
    DWORD redword; 
    if( !::ReadFile(rPipe,buf,BUFFER_SIZE,&redword,0) )
    {
        DWORD error = ::GetLastError();
        //throw new Exception( "Error " + error ); //or something similar
    }
    if( redword == 0 )
        break;
    buf[redword] = '\0';
    string cstemp = buf;
    csoutput += cstemp;
}
return csoutput;