How do i run a program from another program and pass data to it via stdin in c or c++?

Question

Say i have an exe, lets say sum.exe. Now say the code for sum.exe is

void main ()
{
 int a,b;
 scanf (\"%d%d\", &a, &b);
 printf (\"%d\", a+b);
}
         


        

Answer 1

This is my solution and it worked:

sum.cpp

#include "stdio.h"
int main (){
  int a,b;
  scanf ("%d%d", &a, &b);
  printf ("%d", a+b);
  return 0;
}

test.cpp

#include 
#include 

int main(){
  system("./sum.exe < data.txt");
  return 0;
}

data.txt

3 4

Try this solution :)