feat: update structure

cs2106/labs/lab3/progs/part1/sema-right.c

@@ -0,0 +1,32 @@
+//
+// Program to create shared semaphores
+//
+
+#include <semaphore.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/shm.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+int main() {
+  int shmid, pid;
+  sem_t *sem;
+
+  shmid = shmget(IPC_PRIVATE, sizeof(sem_t), IPC_CREAT | 0600);
+  sem = (sem_t *)shmat(shmid, NULL, 0);
+
+  sem_init(sem, 1, 0);
+
+  if ((pid = fork()) != 0) {
+    printf("Parent!. Making my child wait for 1 second.\n");
+    sleep(1);
+    sem_post(sem);
+    wait(NULL);
+    sem_destroy(sem);
+    shmctl(shmid, IPC_RMID, 0);
+  } else {
+    sem_wait(sem);
+    printf("Child! Waited 1 second for parent.\n");
+  }
+}