How do I call ::CreateProcess in c++ to launch a Windows executable?

Question

Something like this:

STARTUPINFO info={sizeof(info)};
PROCESS_INFORMATION processInfo;
if (CreateProcess(path, cmd, NULL, NULL, TRUE, 0, NULL, NULL, &info, &processInfo))
{
    WaitForSingleObject(processInfo.hProcess, INFINITE);
    CloseHandle(processInfo.hProcess);
    CloseHandle(processInfo.hThread);
}

There is an example at http://msdn.microsoft.com/en-us/library/ms682512(VS.85).aspx

Just replace the argv[1] with your constant or variable containing the program.

#include <windows.h>
#include <stdio.h>
#include <tchar.h>

void _tmain( int argc, TCHAR *argv[] )
{
    STARTUPINFO si;
    PROCESS_INFORMATION pi;

    ZeroMemory( &si, sizeof(si) );
    si.cb = sizeof(si);
    ZeroMemory( &pi, sizeof(pi) );

    if( argc != 2 )
    {
        printf("Usage: %s [cmdline]\n", argv[0]);
        return;
    }

    // Start the child process. 
    if( !CreateProcess( NULL,   // No module name (use command line)
        argv[1],        // Command line
        NULL,           // Process handle not inheritable
        NULL,           // Thread handle not inheritable
        FALSE,          // Set handle inheritance to FALSE
        0,              // No creation flags
        NULL,           // Use parent's environment block
        NULL,           // Use parent's starting directory 
        &si,            // Pointer to STARTUPINFO structure
        &pi )           // Pointer to PROCESS_INFORMATION structure
    ) 
    {
        printf( "CreateProcess failed (%d).\n", GetLastError() );
        return;
    }

    // Wait until child process exits.
    WaitForSingleObject( pi.hProcess, INFINITE );

    // Close process and thread handles. 
    CloseHandle( pi.hProcess );
    CloseHandle( pi.hThread );
}

If you application is a Windows GUI application then using the code below to do the waiting is not ideal as messages for your application will not be getting processing. To the user it will look like your application has hung.

WaitForSingleObject(&processInfo.hProcess, INFINITE)

Something like the untested code below might be better as it will keep processing the windows message queue and your application will remain responsive:

//-- wait for the process to finish
while (true)
{
  //-- see if the task has terminated
  DWORD dwExitCode = WaitForSingleObject(ProcessInfo.hProcess, 0);

  if (   (dwExitCode == WAIT_FAILED   )
      || (dwExitCode == WAIT_OBJECT_0 )
      || (dwExitCode == WAIT_ABANDONED) )
  {
    DWORD dwExitCode;

    //-- get the process exit code
    GetExitCodeProcess(ProcessInfo.hProcess, &dwExitCode);

    //-- the task has ended so close the handle
    CloseHandle(ProcessInfo.hThread);
    CloseHandle(ProcessInfo.hProcess);

    //-- save the exit code
    lExitCode = dwExitCode;

    return;
  }
  else
  {
    //-- see if there are any message that need to be processed
    while (PeekMessage(&message.msg, 0, 0, 0, PM_NOREMOVE))
    {
      if (message.msg.message == WM_QUIT)
      {
        return;
      }

      //-- process the message queue
      if (GetMessage(&message.msg, 0, 0, 0))
      {
        //-- process the message
        TranslateMessage(&pMessage->msg);
        DispatchMessage(&pMessage->msg);
      }
    }
  }
}

if your exe happens to be a console app, you might be interested in reading the stdout and stderr -- for that, I'll humbly refer you to this example:

http://support.microsoft.com/default.aspx?scid=kb;EN-US;q190351

It's a bit of a mouthful of code, but I've used variations of this code to spawn and read.

On a semi-related note, if you want to start a process that has more privileges than your current process (say, launching an admin app, which requires Administrator rights, from the main app running as a normal user), you can't do so using CreateProcess() on Vista since it won't trigger the UAC dialog (assuming it is enabled). The UAC dialog is triggered when using ShellExecute(), though.

Here is a new example that works on windows 10. When using the windows10 sdk you have to use CreateProcessW instead. This example is commented and hopefully self explanatory.

#ifdef _WIN32
#include <Windows.h>
#include <iostream>
#include <stdio.h>
#include <tchar.h>
#include <cstdlib>
#include <string>
#include <algorithm>

class process
{
public:

    static PROCESS_INFORMATION launchProcess(std::string app, std::string arg)
    {

        // Prepare handles.
        STARTUPINFO si;
        PROCESS_INFORMATION pi; // The function returns this
        ZeroMemory( &si, sizeof(si) );
        si.cb = sizeof(si);
        ZeroMemory( &pi, sizeof(pi) );

        //Prepare CreateProcess args
        std::wstring app_w(app.length(), L' '); // Make room for characters
        std::copy(app.begin(), app.end(), app_w.begin()); // Copy string to wstring.

        std::wstring arg_w(arg.length(), L' '); // Make room for characters
        std::copy(arg.begin(), arg.end(), arg_w.begin()); // Copy string to wstring.

        std::wstring input = app_w + L" " + arg_w;
        wchar_t* arg_concat = const_cast<wchar_t*>( input.c_str() );
        const wchar_t* app_const = app_w.c_str();

        // Start the child process.
        if( !CreateProcessW(
            app_const,      // app path
            arg_concat,     // Command line (needs to include app path as first argument. args seperated by whitepace)
            NULL,           // Process handle not inheritable
            NULL,           // Thread handle not inheritable
            FALSE,          // Set handle inheritance to FALSE
            0,              // No creation flags
            NULL,           // Use parent's environment block
            NULL,           // Use parent's starting directory
            &si,            // Pointer to STARTUPINFO structure
            &pi )           // Pointer to PROCESS_INFORMATION structure
        )
        {
            printf( "CreateProcess failed (%d).\n", GetLastError() );
            throw std::exception("Could not create child process");
        }
        else
        {
            std::cout << "[          ] Successfully launched child process" << std::endl;
        }

        // Return process handle
        return pi;
    }

    static bool checkIfProcessIsActive(PROCESS_INFORMATION pi)
    {
        // Check if handle is closed
            if ( pi.hProcess == NULL )
            {
                printf( "Process handle is closed or invalid (%d).\n", GetLastError());
                return FALSE;
            }

        // If handle open, check if process is active
        DWORD lpExitCode = 0;
        if( GetExitCodeProcess(pi.hProcess, &lpExitCode) == 0)
        {
            printf( "Cannot return exit code (%d).\n", GetLastError() );
            throw std::exception("Cannot return exit code");
        }
        else
        {
            if (lpExitCode == STILL_ACTIVE)
            {
                return TRUE;
            }
            else
            {
                return FALSE;
            }
        }
    }

    static bool stopProcess( PROCESS_INFORMATION &pi)
    {
        // Check if handle is invalid or has allready been closed
            if ( pi.hProcess == NULL )
            {
                printf( "Process handle invalid. Possibly allready been closed (%d).\n");
                return 0;
            }

        // Terminate Process
            if( !TerminateProcess(pi.hProcess,1))
            {
                printf( "ExitProcess failed (%d).\n", GetLastError() );
                return 0;
            }

        // Wait until child process exits.
            if( WaitForSingleObject( pi.hProcess, INFINITE ) == WAIT_FAILED)
            {
                printf( "Wait for exit process failed(%d).\n", GetLastError() );
                return 0;
            }

        // Close process and thread handles.
            if( !CloseHandle( pi.hProcess ))
            {
                printf( "Cannot close process handle(%d).\n", GetLastError() );
                return 0;
            }
            else
            {
                pi.hProcess = NULL;
            }

            if( !CloseHandle( pi.hThread ))
            {
                printf( "Cannot close thread handle (%d).\n", GetLastError() );
                return 0;
            }
            else
            {
                 pi.hProcess = NULL;
            }
            return 1;
    }
};//class process
#endif //win32