This is a little popen implementation which will make it easier to kill processes and will give you access to the PID of the process, I don't know why they didn't do this in popen but I'm sure they had good reasons because those guys are way too smart...

This code was inspired by many sources and I think I perfected it, although you might find bugs or issues and if you do, please let me know if the comments section.
You can use it like so:

struct popen_plus_process *process = popen_plus("ls -l");
if (!process) {
     /* Failed do something and return or exit */
     return -1;
}

int MAX_BUFFER = 256;
char buffer[256];

while (!feof(process->read_fp))
     if (fgets(buffer, MAX_BUFFER, process->read_fp) != NULL)
          printf("%s\n", buffer);

popen_plus_close(process);

To kill a process:

popen_plus_kill(process);
popen_plus_close(process);

Terminate is the same...