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

In C on platforms whose name end with X (i.e. not Windows), the key components are:

1. pipe - Returns a pair of file descriptors, so that what's written to one can be read from the other.

2. fork - Forks the process to two, both keep running the same code.

3. dup2 - Renumbers file descriptors. With this, you can take one end of a pipe and turn it into stdin or stdout.

4. exec - Stop running the current program, start running another, in the same process.

Combine them all, and you can get what you asked for.