I need to write a program in C that will:

1. create child process (child_process1)
2. print PID of parent process using getppid()
3. the child_process1 will create another subprocess (child_process2)
4. child_process2 will print PID of parent process (child_process1) using getppid() and its own PID using getpid()

So far, I’ve written something like that:

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

int main(int argc, char *argv[])
{
    //declaration of PID holding variables
    pid_t child1, child2;
    pid_t child1_PID, child2_PID;
    //forking parent process
    child1 = fork();
    //redeclaring PID so as to omit double execution of code by both parent and child processes
    child1_PID = child1;
    //check whether child1_PID contains PID of a child process
    if(child1_PID == 0){
        //print PID of parent process
        printf("%dn",getppid());
        //make child process child1 fork child process child2
        child2 = fork();
        //redeclaring PID so as to omit double execution of code by both parent and child processes
        child2_PID = child2;
        //check whether child2_PID contains PID of a child process
        if(child2_PID == 0){
            //print PID of parent process of child process child2 (child1)
            printf("%dn",getppid());
            //print PID of child process child2
            printf("%dn",getpid());
        }
    }
    return 0;
}

But the code doesn’t seem to work the way I want. Furthermore, sometimes it prints 4 PIDs, sometimes only one.