Update MentOs code to the latest development version.

programs/tests/t_groups.c

@@ -0,0 +1,39 @@
+///                MentOS, The Mentoring Operating system project
+/// @file t_groups.c
+/// @brief
+/// @copyright (c) 2014-2021 This file is distributed under the MIT License.
+/// See LICENSE.md for details.
+
+#include <sys/unistd.h>
+#include <sys/wait.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <time.h>
+
+int main(int argc, char **argv)
+{
+    pid_t gid = getgid();
+    pid_t pid = getpid();
+    pid_t sid = getsid(0);
+
+    printf("pid: %d, gid: %d, sid: %d\n\n", pid, gid, sid);
+    for (int i = 0; i < 5; ++i) {
+        if (fork() == 0) {
+            pid_t gid_child  = getgid();
+            pid_t pid_child  = getpid();
+            
+            pid_t ppid_child = getppid();
+            pid_t sid_child  = getsid(ppid_child);
+
+            printf("%d) pid_child: %d, gid_child: %d, ppid_child: %d, sid_child: %d\n",
+                   i, pid_child, gid_child, ppid_child, sid_child);
+            sleep(5);
+            exit(0);
+        }
+    }
+    //int status;
+    //while (wait(&status) > 0)
+    //    ;
+
+    return 0;
+}