simple join example

threads-sema/join.c

@@ -0,0 +1,27 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <unistd.h>
+
+#include "common.h"
+#include "common_threads.h"
+
+sem_t s;
+
+void *child(void *arg) {
+    sleep(4);
+    printf("child\n");
+    Sem_post(&s); // signal here: child is done
+    return NULL;
+}
+
+int main(int argc, char *argv[]) {
+    Sem_init(&s, 0); 
+    printf("parent: begin\n");
+    pthread_t c;
+    Pthread_create(&c, NULL, child, NULL);
+    Sem_wait(&s); // wait here for child
+    printf("parent: end\n");
+    return 0;
+}
+