init commit

3sem/exam/sem3.c

@@ -0,0 +1,38 @@
+#include <unistd.h>
+#include <sys/shm.h>
+#include <sys/sem.h>
+#include <fcntl.h>
+
+struct record
+{
+    double dbl, int num,
+}
+
+int
+main(int argc, char **argv)
+{
+    int shm_key = shmget(IPC_PRIVATE, sizeof(record), IPC_CREAT | 0666);
+    int sem_key = semget(IPC_PRIVATE, 1, IPC_CREAT | 0666);
+
+    record *mem = shmat(shm_key, NULL, 0);
+
+    for (int i = 1; i < argc; ++i) {
+        int fd = open(argv[i], O_RDONLY);
+        double sum = 0;
+        int num = 0;
+        double tmp;
+
+                while (read(fd, &tmp, sizeof(tmp)) {
+            num++;
+            sum += tmp;
+		}
+		semop(sem_key, &(struct sembuf){.sem_num = 0, .sem_op = -2}, 1);
+		*mem = (struct record){.dbl = sum, .num = num};
+		semop(sem_key, &(struct sembuf){.sem_num = 0, .sem_op = -1}, 1);
+    }
+
+    while (wait(NULL) != -1) {
+    }
+
+    return 0;
+}