Aargh mailslots and the like!!

Hi guys,

i just registered, and since there is no point in lying.... ill tell you straight off. Im a inforatics student from holland, and i have an home work assignment... BUT i dont want you guys making it for me but help me with... So here goes:

I need to write a C++ program which starts 3 (with help from createprocess) ms-dos boxes each printing a, b, c when it their turn. So first box 1 prints a then box 2 prints a then box three prints a and after this box 1 prints b, and so forth and so on...
But when only one ms-box is running it will print: abcabcabcabc etc, etc.

This process needs to be synchronized with mailslots...

Ok im just beginnen but this is what i have so far:

Code:

---

void main()

{
  // Set the startup information
  STARTUPINFO startup_info = {0};
  startup_info.cb = sizeof startup_info;
  PROCESS_INFORMATION pi = {0};

  // Create the process
 CreateProcess("D:\\ipc\\opdracht\\debug\\printer.exe", "D:\\ipc\\opdracht\\debug\\printer.exe", NULL, NULL, FALSE, 0, NULL, NULL, &startup_info, &pi);
}

---

Where printer.exe is the program which prints abcabcbabc....
But i need three of those boxes, simply copying the piece of code i have three times doesn't work.... anybody wiling to help a lost soul here?

Hi, welcome to the boards. For future reference a question about windows api function can elict more responses on the windows board.

In the processes you create(output processes) you need to:
- Create a mailslot.
- Listen on that mailslot.
- Write to output when told to.

In the master process you need to:
- Create the output processes.
- Connect to their mailslots.
- Write to their mailslots to tell them to continue.

Sample for output process:

Code:

---

int main(void)
{
        HANDLE hSlot = CreateMailslot("\\\\.\\mailslot\\msname", 0,  MAILSLOT_WAIT_FOREVER,  NULL);

        while (TRUE)
        {
                ReadFile(hSlot, buf, sizeof(buf), &dwRead, NULL); // Receive message from master.
                printf("%s", buf); // print what the master has told us to.
        }
}

---

Sample for master process:

Code:

---

int main(void)
{

        // Create Processes

        // Connect to mailslots.
        hSlot1 = CreateFile("\\\\.\\mailslot\\msname", ...);

        // Write to mailslots what you want them to output.
        WriteFile(hSlot1, "test", 4, ...);
}

---

Things to think about:
- You need a different name for each mailslot (maybe pass the name you want the output process to use on the command line).
- You need to make sure that the master process does not try to connect to a mailslot before it is created.

Hey man thanks for your help, really! And thanks for the tip, i posted my updated problems ;) in the other section of the board, so if anyone is willing to take a risk and a look its over here: http://cboard.cprogramming.com/showt...threadid=50080