Update MentOs code to the latest development version.

programs/nice.c

@@ -0,0 +1,35 @@
+///                MentOS, The Mentoring Operating system project
+/// @file nice.c
+/// @brief
+/// @copyright (c) 2014-2021 This file is distributed under the MIT License.
+/// See LICENSE.md for details.
+
+#include <sys/unistd.h>
+#include <string.h>
+#include <stdio.h>
+
+int main(int argc, char** argv)
+{
+    if (argc == 1) {
+        int current = nice(0);
+        printf("%d \n\n", current);
+        return 0;
+    }
+    if (argc != 2) {
+        printf("%s: missing operand.\n", argv[0]);
+        printf("Try '%s --help' for more information.\n\n", argv[0]);
+        return 1;
+    }
+    if (!strcmp(argv[1], "--help")) {
+        printf("Usage: %s <increment>\n\n", argv[0]);
+        return 0;
+    }
+    int increment = atoi(argv[1]);
+    if ((increment < -40) || (increment > 40)) {
+        printf("Error: You must provide a value between (-40,+40). \n\n", increment);
+        return 1;
+    }
+    int newNice = nice(increment);
+    printf("Your new nice value is %d.\n\n", newNice);
+    return 0;
+}