feat: update structure

cs2106/labs/lab3/progs/part1/lab3p1-shm.c

@@ -0,0 +1,43 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/shm.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#define NUM_PROCESSES 5
+
+int main() {
+
+  int i, j, pid;
+
+  int *turn;
+  int shmid;
+
+  shmid = shmget(IPC_PRIVATE, sizeof(int), IPC_CREAT | 0600);
+  turn = shmat(shmid, NULL, 0);
+  turn[0] = 0;
+
+  for (i = 0; i < NUM_PROCESSES; i++) {
+    if ((pid = fork()) == 0) {
+      break;
+    }
+  }
+
+  if (pid == 0) {
+    while (turn[0] != i)
+      ;
+    printf("I am child %d\n", i);
+
+    for (j = i * 10; j < i * 10 + 10; j++) {
+      printf("%d ", j);
+      fflush(stdout);
+      usleep(250000);
+    }
+
+    printf("\n\n");
+    turn[0] = i + 1;
+  } else {
+    for (i = 0; i < NUM_PROCESSES; i++)
+      wait(NULL);
+  }
+}