question about piping to external programs

I've been experimenting with piping to external programs in the last few days and have gain no grounds.

Code:

#include <cstdlib>
#include <iostream>
using namespace std;
int main(int argc, char *argv[])
{   
    string aa = "test";
     echo -e aa | test2.exe;    // doesn't work
     system("aa | test2.exe "); //doesn't work either
     system("PAUSE");
    return EXIT_SUCCESS;
}

Code for test2.exe:

Code:

#include <cstdlib>
#include <iostream>
using namespace std;
int main(int argc, char *argv[])
{    
    string bb; 
    cout << "Please enter stuff: ";
    cin  >> bb;
    cout << bb; 
    system("PAUSE");
    return EXIT_SUCCESS;
}

It would be nice if someone could tell me how to make a pipe. It seems quite simple from those tutorials, however I just can't seem to grasp it and make it work in my code.

_popen, _wpopen (CRT)

Thanks, trying to figure out the example code now.

Code:

  if( (pPipe = _popen( "dir *.c /on /p", "rt" )) == NULL )
      exit( 1 );

I don't really get the line above.

I'm assuming it's referning to
dir =Directory
*=at
.c =C drive
/on= ??
/p= ??
r= The calling process can read the spawned command's standard output via the returned stream
t = Open in text mode.

What's /on and /p? I tired googling it but google doesn't read "/"

if i want to run a program called "test2.exe" would it be

pPipe = _popen( "dir *.c test2.exe", "rt" ))

The * represents a wildcard (0 or more characters). So "*.c" represents all filenames ending in ".c" (or all files with extension "c") in the current working directory.

As for the other arguments to dir:
Command Reference: dir - Microsoft

/o[[:]<SortOrder>]
Sorts the output according to SortOrder, which can be any combination of the following values:

...
n By name (alphabetical)
...

/p

Displays one screen of the listing at a time. To see the next screen, press any key on the keyboard.