C communicate parent and child to increase and print counter - c

Question

I am trying to write a program so that the parent and child process can communicate back and forth between each other. The parent process and the child process ought to print the values from 1-100 where each process prints the value incrementing it by 1 each time. Now the issue I face is that, I know nothing much about pipes. What I gather from reading materials online is that I can use a pipe to read and write values. I have leveraged this to print something in the child process, and send back something to the parent. Now, I am not sure how to get the parent to return to the child after printing for itself? I know my code is probably all wrong, but I am really not sure what I should do.
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
int main(int argc, const char * argv[]) {
int fd[2];
if (pipe(fd)== -1){
printf("An error occured while opening the pipe\n");
}
int id = fork();
int i = 0;
if (id == 0){
close(fd[0]);
printf("In child: %d", i);
i ++;
write(fd[1], &i, sizeof(int));
close(fd[1]);
} else {
wait(NULL);
close(fd[1]);
int y;
read(fd[0],&y, sizeof(int));
close(fd[0]);
}
}

Answer 1

To keep it simple, it's up to you to check return values and handle errors. This will only do it between 0 - 9 and you will have to expand the mathematics.
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
int main(int argc, char *argv[])
{
int pipefd_1[2];
int pipefd_2[2];
pid_t cpid;
pipe(pipefd_1);
pipe(pipefd_2);
cpid = fork();
if (cpid == 0) { /* Child reads from pipe 1, writes to pipe 2*/
char cval[] = {'0'};
close(pipefd_1[1]); /* Close unused write and read ends */
close(pipefd_2[0]);
while (atoi(cval) != 9) {
read(pipefd_1[0], cval, 1);
printf("Child print %d\n", atoi(cval));
cval[0] += 1;
write(pipefd_2[1], cval, 1);
}
} else {
char cval[] = {'0'}; /* Parent writes buf to pipe 1 */
close(pipefd_1[0]); /* Close unused read end */
close(pipefd_2[1]);
while (atoi(cval) != 9) {
write(pipefd_1[1], cval, 1);
read(pipefd_2[0], cval, 1);
printf("Parent print %d\n", atoi(cval));
cval[0] += 1;
}
}
}
Output