HowToForkInC

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>

//this code must be run in an unix env


int main(int argc, char *argv[]){

    pid_t pid;
    //get parent pid before the fork
    //getpid will change for child after fork
    //the parent will still have the same pi
    pid_t parentPid =  getpid();
    fork();

    pid = getpid();

    //do sometihng in the child proces
    if(pid != parentPid){
        printf("\nHello from child process pid %d", pid);
    }

    //do something in the parent process
    if(pid == parentPid){
        printf("\nHello from parent process pid %d", pid);
    }

    printf("\nhello world from both... one each in the fork\n");

    fork();

    pid_t gpid = getpid();

    if(gpid != parentPid && gpid != pid)
       printf("\nHello from the grandchildren %d\n", gpid);

    return 0;

}