1

#include <stdio.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <unistd.h>
#include <stdlib.h>


void child() {
	printf("child\n");
	return;
}

int main() {
	// get key
	key_t shmKey = ftok("/tmp", 1);
	key_t semKey = ftok("/tmp", 2);
	printf("shmkey = %d semkey = %d\n", (int)shmKey, (int)semKey);

	// create shm
	int shmid = shmget(shmKey, 3 * sizeof(int), IPC_CREAT | 0600);
	printf("shm id %d\n", shmid);
	// attach shm
	int *shm = (int *) shmat(shmid, NULL, 0);
	printf("shm ptr %p\n", shm);

	// create sem
	int semid = semget(semKey, 2, IPC_CREAT | 0600);


	sleep(3);

	// detach shm
	shmdt(shm);
	// remove shm
	shmctl(shmid, IPC_RMID, 0);
	
	int pid = fork();
	if(pid == 0) {
		child();
		exit(0);
	}
	printf("main\n");
	return 0;
}

 #include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/ipc.h>
#include <sys/sem.h>

void make(int id) {
	srand(time(0));
	for(int i=0;i<6;i++) {
		// add data
		usleep(rand() % 1000000);
		int data = rand();
		printf("W-%d-%d -> %d\n", id, i, data);
	}
}

void use(int id) {
	srand(time(0));
	for(int i=0;i<6;i++) {
		// get data
		usleep(rand() % 1000000);
		int data;
		data = rand();
		printf("R-%d-%d <- %d\n", id, i, data);
	}
}

int main() {
	int *child = (int*)malloc(5*sizeof(int));
	int child_cnt;
	for(int i=0;i<2;i++) {
		// maker
		int pid = fork();
		if(pid == 0) {
			// child process
			make(i);
			exit(0);
		}
		else {
			child[child_cnt++] = pid;
		}
	}
	for(int i=0;i<3;i++) {
		// user
		int pid = fork();
		if(pid == 0) {
			use(i);
			exit(0);
		}
		else {
			child[child_cnt++] = pid;
		}
	}
	for(int i=0;i<child_cnt;i++) {
		waitpid(child[i], NULL, 0);
	}
	return 0;
}