How to fork() two processes simultaneously - c++

Question

I made some headway on my program by allowing it to run for a random number of time between 0 and 20 using rand()%20. However, I cannot figure out how to fork() off multiple processes, 2 maximum.
If I understand fork() correctly, I have created 1 parent and 1 child process in my program. The rand1 value in
else if (pid==0) {
mypid = getpid();
cout << "Child pid is " << mypid << "\n";
execlp("./idle","./idle","1",rand1,0); }
in execlp will create and run the ./idle processes for whatever was generated, correct? For example if rand1 == 19, each process, parent and child, will run for 19 seconds before the program finishes, not including the sleep() timers in the code.
Now my main problem is forking two processes so that I'm not simply left with 1 parent and 1 child, but rather 2 parents and 2 children, but running through the program as it currently works.
I'm lost and hopefully some guidance can come from this post's future replies.
Thank you!
#include <iostream>
#include <unistd.h>
#include <sys/wait.h>
#include <cstdlib>
#include <time.h>
using namespace std;
using std::cout;
volatile sig_atomic_t keep_going = 2;
void catch_child (int sig)
{ int status, p;
p = waitpid(-1,&status,WNOHANG);
if (p==0) return;
keep_going=0;
cout<<"Child process caught: "<< p <<endl;
return;
}
int main()
{
pid_t pid;
pid_t mypid;
int rand1;
int i;
srand(time(NULL)); //init seed
rand1 = rand()%20; //generates random number 0 - 20
cout << "This is the random number (rand1): " << rand1 << "\n"; //output to see how long
signal (SIGCHLD, catch_child); //when child is sent, run function catch_child
pid = fork();
if (pid<0) {
cout<<"Error\n";
return 0;
}
else if (pid==0) {
mypid = getpid();
cout << "Child pid is " << mypid << "\n";
execlp("./idle","./idle","1",rand1,0);
} else {
mypid=getpid();
cout<<"Parent procss is " << mypid << " and child is " << pid << "\n";
sleep(3);
cout<<"Pausing child " << pid <<" for " << rand1 << " seconds\n";
kill(pid,SIGSTOP);
for (int i=0; i < rand1; i++) sleep(3);
cout<<"Resuming child "<<pid<<"\n";
kill(pid,SIGCONT);
cout<<"Parent process pid is "<<mypid<<" waiting for child to stop\n";
while (keep_going==rand1) sleep(2);
cout <<"Parent knows that Child now done\n";
}
return 0;
} //keep
UPDATE:
Here's a sample run of what appears to be a semi working program. Attached is the code and an image regarding the sample run with the updated code below.
#include <iostream>
#include <unistd.h>
#include <sys/wait.h>
#include <cstdlib>
#include <time.h>
using namespace std;
using std::cout;
volatile sig_atomic_t keep_going = 2;
void catch_child (int sig)
{ int status, p;
p = waitpid(-1,&status,WNOHANG);
if (p==0) return;
keep_going=0;
cout<<"Child process caught: "<< p <<endl;
return;
}
int main()
{
pid_t pid;
pid_t mypid;
int rand1;
int i;
srand(time(NULL)); //init seed
rand1 = rand()%20; //generates random number 0 - 20
cout << "This is the random number (rand1): " << rand1 << "\n"; //output to see how long
signal (SIGCHLD, catch_child); //when child is sent, run function catch_child
;
for(int i=0;i<2;i++){
pid = fork();
if (pid<0) {
cout<<"Error\n";
return 0;
}
else if (pid==0) {
mypid = getpid();
cout << "Child pid is " << mypid << "\n";
execlp("./idle","./idle","1",rand1,0); //does rand1 make the processes run for rand1's value?
} else {
mypid=getpid();
cout<<"Parent procss is " << mypid << " and child is " << pid << "\n";
sleep(3);
cout<<"Pausing child " << pid <<" for " << rand1 << " seconds\n";
kill(pid,SIGSTOP); //SIGSTOP acts as a PAUSE
for (int i=0; i < rand1; i++) sleep(3);
cout<<"Resuming child " << pid << "\n";
kill(pid,SIGCONT);
cout<<"Parent process pid is "<<mypid<<" waiting for child to stop\n";
while (keep_going==rand1) sleep(2);
cout <<"Parent knows that Child now done\n";
}
}
return 0;
}