Help with CreateProcess()

Hi,

I have a problem using CreateProcess().

Let me show you the code first:

Code:

if(!CreateProcess(NULL,   // No module name (use command line)
   "POI.exe < data1.in > data1.out",        // 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() );
   scanf("%d", &n);
   return 0;
}

(Obviously I copied the code from MSDN and only modified a little :P)

I executed it, and it was sucessfully running POI.exe. However, the input and output are not redirected to data1.in and data1.out. Why is this happening? What's the solution to it?

Thanks in advance.

I/O redirection is handled by the command processor (cmd.exe). You can use system() instead, or take care of the I/O redirection yourself.
Creating a Child Process with Redirected Input and Output (Windows)

gg

The output redirection should be specified in the STARTUPINFO struct; first open a handle to the in and out files and then use those handles in the struct:

Code:

STARTUPINFO si;
HANDLE hin,hout;

hin=CreateFile(...);//for reading
hout=CreateFile(...);//for writing

memset(&si,0,sizeof(si));
si.cb=sizeof(si);
si.dwFlags=STARTF_USESTDHANDLES;
si.hStdInput=hin;
si.hStdOutput=hout;

//remember to close the handles

If you like you can also redirect the std error output assigning to the hStdError struct's member a handle to an errors file.

Hope that helps
Niara

Oops I've seen it now: I've explained the same as the the Codeplug's link. Sorry.

Niara

Thanks for your help. But now I'm having trouble with this code:

Code:

   STARTUPINFO si;
   PROCESS_INFORMATION pi;

   HANDLE hin = CreateFile("data1.in", GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
   if(hin == INVALID_HANDLE_VALUE){
      printf("in error %d\n", GetLastError());
   }
   HANDLE hout = CreateFile("data1.out", GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
   if(hout == INVALID_HANDLE_VALUE){
      printf("out error %d\n", GetLastError());
   }

   ZeroMemory(&si, sizeof(si));
   si.cb = sizeof(si);
   si.dwFlags = STARTF_USESTDHANDLES;
   si.hStdInput = hin;
   si.hStdOutput = hout;
   ZeroMemory(&pi, sizeof(pi));

   if(!CreateProcess(NULL,   // No module name (use command line)
      "POI",        // 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() );
      scanf("%d", &n);
      return 0;
   }

It seems that the input is not working, but hin != INVALID_HANDLE_VALUE, and somehow the POI.exe just seems not to read from data1.in at all and the whole program is stuck. Any ideas?

Thanks.

Call SetHandleInformation() on hin and hout - like in the article I posted.
The 5th parameter to CreateProcess() should be TRUE.

gg

This is still not working?

Code:

   STARTUPINFO si;
   PROCESS_INFORMATION pi;

   HANDLE hin = CreateFile("data1.in", GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
   if (!SetHandleInformation(hin, HANDLE_FLAG_INHERIT, 0)){
      printf("set in handle error %d", GetLastError());
      scanf("%d", &n);
      return 0;
   }
   if(hin == INVALID_HANDLE_VALUE){
      printf("in error %d\n", GetLastError());
   }
   HANDLE hout = CreateFile("data1.out", GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
   if (!SetHandleInformation(hout, HANDLE_FLAG_INHERIT, 0)){
      printf("set out handle error %d", GetLastError());
      scanf("%d", &n);
      return 0;
   }
   if(hout == INVALID_HANDLE_VALUE){
      printf("out error %d\n", GetLastError());
   }

   ZeroMemory(&si, sizeof(si));
   si.cb = sizeof(si);
   si.dwFlags = STARTF_USESTDHANDLES;
   si.hStdInput = hin;
   si.hStdOutput = hout;
   ZeroMemory(&pi, sizeof(pi));

   if(!CreateProcess(NULL,   // No module name (use command line)
      "POI",        // Command line
      NULL,           // Process handle not inheritable
      NULL,           // Thread handle not inheritable
      TRUE,          // Set handle inheritance to TRUE
      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() );
      scanf("%d", &n);
      return 0;
   }

I get error no.5 when setting the hin handle.

Error 5 is access denied. Probably that means data1.in doesn't exist (where the computer thinks it should). It should be in the current working directory, which IIRC is not the directory where your executable is (i.e., not Debug or Release but the one above that).

data1.in is in the directory my executable is in, how should I do it?

Check for INVALID_HANDLE_VALUE after CreateFile. Then call SetHandleInformation on both hin and hout.

Then you should wait for the process the exit.

gg

Originally Posted by jasperleeabc

data1.in is in the directory my executable is in, how should I do it?

Perhaps I'm hallucinating again, but I believe that is not the right place for it. It shoudl be up one directory level.

I don't have any errors printed now, but it's still not reading from data1.in...

Code:

Code:

   STARTUPINFO si;
   PROCESS_INFORMATION pi;

   HANDLE hin = CreateFile("E:\\Personal Data\\Jasper's Stuff\\C\\IOI 2009\\Day 1\\data1.in", GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
   if(hin == INVALID_HANDLE_VALUE){
      printf("in error %d\n", GetLastError());
   }
   if (!SetHandleInformation(hin, HANDLE_FLAG_INHERIT, 0)){
      printf("set in handle error %d", GetLastError());
      scanf("%d", &n);
      return 0;
   }
   HANDLE hout = CreateFile("E:\\Personal Data\\Jasper's Stuff\\C\\IOI 2009\\Day 1\\data1.out", GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
   if(hout == INVALID_HANDLE_VALUE){
      printf("out error %d\n", GetLastError());
   }
   if (!SetHandleInformation(hout, HANDLE_FLAG_INHERIT, 0)){
      printf("set out handle error %d", GetLastError());
      scanf("%d", &n);
      return 0;
   }
   ZeroMemory(&si, sizeof(si));
   si.cb = sizeof(si);
   si.dwFlags = STARTF_USESTDHANDLES;
   si.hStdInput = hin;
   si.hStdOutput = hout;
   ZeroMemory(&pi, sizeof(pi));

   if(!CreateProcess(NULL,   // No module name (use command line)
      "POI",        // Command line
      NULL,           // Process handle not inheritable
      NULL,           // Thread handle not inheritable
      TRUE,          // Set handle inheritance to TRUE
      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() );
      scanf("%d", &n);
      return 0;
   }

My program is like now stuck and can't do anything.

>> Call SetHandleInformation() on hin and hout - like in the article I posted.
Well, not *exactly* like in the article. You want hin and hout to be inheritable, but you're clearing HANDLE_FLAG_INHERIT instead of setting it.

gg

Problem solved, many thanks!