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

Question

Looking for an example that    Launches an EXE Waits for the EXE to finish  Properly closes all the handles when the executable finishes

User · Answer

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);
      }
    }
  }
}

User · Answer

Perhaps this is the most complete  http   goffconcepts com techarticles development cpp createprocess html

User · Answer

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  lt Windows h gt   include  lt iostream gt   include  lt stdio h gt   include  lt tchar h gt   include  lt cstdlib gt   include  lt string gt   include  lt algorithm gt   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   amp si  sizeof si             si cb   sizeof si           ZeroMemory   amp 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 lt wchar t  gt   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              amp si                Pointer to STARTUPINFO structure              amp pi                Pointer to PROCESS INFORMATION structure                                 printf   CreateProcess failed   d   n   GetLastError                  throw std  exception  Could not create child process                      else                       std  cout  lt  lt                Successfully launched child process   lt  lt  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   amp 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  amp 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

User · Answer

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

User · Answer

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

User · Answer

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  lt windows h gt   include  lt stdio h gt   include  lt tchar h gt   void  tmain  int argc  TCHAR  argv           STARTUPINFO si      PROCESS INFORMATION pi       ZeroMemory   amp si  sizeof si         si cb   sizeof si       ZeroMemory   amp 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           amp si                Pointer to STARTUPINFO structure          amp 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

User · Answer

Bear in mind that using WaitForSingleObject can get you into trouble in this scenario  The following is snipped from a tip on my website      The problem arises because your application has a window but isn t pumping messages  If the spawned application invokes SendMessage with one of the broadcast targets  HWND BROADCAST or HWND TOPMOST   then the SendMessage won t return to the new application until all applications have handled the message - but your app can t handle the message because it isn t pumping messages     so the new app locks up  so your wait never succeeds     DEADLOCK    If you have absolute control over the spawned application  then there are measures you can take  such as using SendMessageTimeout rather than SendMessage  e g  for DDE initiations  if anybody is still using that   But there are situations which cause implicit SendMessage broadcasts over which you have no control  such as using the SetSysColors API for instance   The only safe ways round this are    split off the Wait into a separate thread  or  use a timeout on the Wait and use PeekMessage in your Wait loop to ensure that you pump messages  or  use the MsgWaitForMultipleObjects API

User · Answer

Something like this   STARTUPINFO info  sizeof info    PROCESS INFORMATION processInfo  if  CreateProcess path  cmd  NULL  NULL  TRUE  0  NULL  NULL   amp info   amp processInfo         WaitForSingleObject processInfo hProcess  INFINITE       CloseHandle processInfo hProcess       CloseHandle processInfo hThread

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