Question about _popen

[cunnus88]

After foraging about here and there, I found a way to run a subprocess from my program (if that's the right way to call it).
All in all, it runs the way I want it to, but there's a slight tick with it that I want to get rid of.
If I want to display the output from the subprocess, I can't write to it, but if I write to it, I can't get output from it.

Here's the offending line of code:

if( (pPipe = _popen( "xfst", "wr" )) == NULL )
      exit( 1 );

If I change the ordering of the second argument in _popen to "rw", I can't pass input to it. It's fine the way it is right now, but I would like to see what's going on, while I'm at it.

Here's the entire body of the code:

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

using namespace std;

int main()
{
   char   psBuffer[128];
   FILE   *pPipe;

   if( (pPipe = _popen( "xfst", "wr" )) == NULL )
      exit( 1 );

   while( !strcmp("\n", psBuffer))
   {
      if( fgets( psBuffer, 128, pPipe ) != NULL )
         printf( psBuffer );
   }
	fprintf(pPipe, "define A [a|b]*;");
	fprintf(pPipe, "exit\n");

	printf( "\nProcess returned %d\n", _pclose( pPipe ) );
	system("pause");
	return 0;
}

[Salem]

popen() is a convenience function which restricts you to one-way communication.

You need to dig deeper and find out the underlying mechanisms for inter-process communication.

[cunnus88]

Thanks for letting me know it's impossible with popen.

I just tried a google search with interprocess communication. It seems it's a field of its own (630,000 results).

One thing I noticed was that the hits on the first page had to do with Unix or Linux and that piping was involved. I'm actually working with Windows, and as far as I know the Windows command line does not have piping built into it (unless you count the ">>" operator).

Would it help me to sift through all that Unix information? If not, could you point me to a good reference site which is relevant to Windows (or OS neutral)?

[Salem]

Since you used _popen(), I'm guessing windows
http://faq.cprogramming.com/cgi-bin/...&id=1043284392

Some solution based around CreateProcess() would be my guess

[cunnus88]

Thanks. Hopefully, my brains will be up to the task.