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Excution of External program

Posted on 1998-09-09
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Last Modified: 2011-09-20
I'm studying Excution of external program. I want a sample code which execute another. The main (Host) application is C++ window program and sub (client) program is based on C or C++. NOT DLL! Processing can be a simple code like 'C=A+B'. Please let me know how process it is. I want to sample! (I know it may bother you if making a sample. ^^, )
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Question by:free096
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LVL 7

Expert Comment

by:faster
ID: 1172406
Just use CreateProcess()
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Author Comment

by:free096
ID: 1172407
I said I needed sample which can run. I can not do it though I know CreateProcess() function.
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Expert Comment

by:faster
ID: 1172408
Sorry, you need a sample.

STARTUPINFO StartupInfo;
PROCESS_INFORMATION ProcessInformation;
char pathbuf[_MAX_PATH];

GetStartupInfo(&StartupInfo);
strcat(pathbuf, "\\path\\a.exe");
CreateProcess(NULL, pszHomeDir, NULL, NULL, FALSE, CREATE_NEW_PROCESS_GROUP | NORMAL_PRIORITY_CLASS, NULL, NULL, &StartupInfo, &ProcessInformation);

I assume that you are using windows, besides CreateProcess, you can also use WinExec().  Another alternative is to use system(), which is a C runtime function so it is also available on other platforms.  However, on windows, CreateProcess() is better.

On UNIX, you can use fork() and execle() (or execlp, execvp ...).  Well, you mentioned Windows, so forget about this.

 
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by:faster
ID: 1172409
Let me know if you have problem using it.
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Author Comment

by:free096
ID: 1172410
Thanks, faster. But still I don't know How app. can exchange data with Client app. Yea, OS is windows, of course. Would you mind showing me both sample of Client & Host which can exchange data like 'C = A + B'. (input A & B into Host, Client calculate it, and  Host must show the result, C)
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Expert Comment

by:faster
ID: 1172411
I see, you are actually talking about IPC.  There are a lot of ways to do it depending on what kind of messages you need to exchange between the parent and the child.  So could you let me know the type and size of the messages (both direction) and do they exchange information frequently or simply a one time process?
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Author Comment

by:free096
ID: 1172412
Thanks, faster, again. Actually I have not heard about IPC. So I have no idea. Are there so many kinds of IPC? Hm... ^^, First of all I want to know just SIMPLE calculation, C=A+B. (It's the starting point. ^^;) I think it's one time process: Host send A&B to Client. and Client send the result, C(=A+B) to Host. And interger type is enough. Can you show me the samples of both Host and Client?
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Accepted Solution

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faster earned 450 total points
ID: 1172413
This is just a simple demo, you need to refine your error checking etc.

Parent:

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


void main()
{
       STARTUPINFO StartupInfo;
     PROCESS_INFORMATION ProcessInformation;
     char pathbuf[_MAX_PATH];
       BOOL bSuccess;
       DWORD r;

     GetStartupInfo(&StartupInfo);
     sprintf(pathbuf, "d:\\faster\\tt\\t2.exe %d %d", 10, 20);
     CreateProcess(NULL, pathbuf, NULL, NULL, FALSE,CREATE_NEW_PROCESS_GROUP | NORMAL_PRIORITY_CLASS, NULL, NULL, &StartupInfo, &ProcessInformation);
       bSuccess = GetExitCodeProcess(ProcessInformation.hProcess, &r);
}


Child:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
      int i,j;

      i = atoi(argv[1]);
      j = atoi(argv[2]);
      return i+j;
}

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Expert Comment

by:faster
ID: 1172414
Note that the server->child communication is by command line, other simple choices include env variable.  But they can only be one time.  Better and more complex way include using a pipe, using windows message (create a window in child), socket, OLE etc.  Child->parent is done using an exit status, this can only work for integer.  A better and still easy way is to use windows message, I mean to create a window in parent with a fixed window name, then the child can find the window handle and then use WM_COPYDATA or other messages to pass data back.  Pipe, socket, OLE etc give you more control.
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LVL 10

Expert Comment

by:viktornet
ID: 1172415
What does the ** in front of the argv means?? in
  int main(int argc, char **argv)

Thanks!

Regards,
Viktor Ivanov
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LVL 7

Expert Comment

by:faster
ID: 1172416
** means a pointer to a list of pointers, that is the standard C stuff
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Author Comment

by:free096
ID: 1172417
Thanks, faster. Your code has some error to debug. Anyway, it looks pretty good. I'll try it. After this, if I had more question, I would ask you. Could I know your Email address? (If question, I'll notify you.)
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