diff --git a/demos/constants.c b/demos/constants.c
index 32af20b..d5d3622 100644
--- a/demos/constants.c
+++ b/demos/constants.c
@@ -8,6 +8,12 @@
  */
 #include "tomcrypt.h"
 
+#if _POSIX_C_SOURCE >= 200112L
+#include <libgen.h>
+#else
+#define basename(x) x
+#endif
+
 /**
   @file demo_crypt_constants.c
 
@@ -17,33 +23,61 @@
   Larry Bugbee, February 2013
 */
 
+static void _print_line(const char* cmd, const char* desc)
+{
+   printf("  %-16s - %s\n", cmd, desc);
+}
 
-int main(void) {
-    /* given a specific constant name, get and print its value */
-    char name[] = "CTR_COUNTER_BIG_ENDIAN";
-    int  value;
-    char *names_list;
-    unsigned int names_list_len;
+int main(int argc, char **argv)
+{
+   if (argc == 1) {
+      /* given a specific constant name, get and print its value */
+      char name[] = "CTR_COUNTER_BIG_ENDIAN";
+      int value;
+      char *names_list;
+      unsigned int names_list_len;
 
-    if (crypt_get_constant(name, &value) != 0)
-      exit(EXIT_FAILURE);
-    printf("\n  %s is %d \n\n", name, value);
+      if (crypt_get_constant(name, &value) != 0) exit(EXIT_FAILURE);
+      printf("\n  %s is %d \n\n", name, value);
 
-    /* get and print the length of the names (and values) list */
+      /* get and print the length of the names (and values) list */
 
-    if (crypt_list_all_constants(NULL, &names_list_len) != 0)
-      exit(EXIT_FAILURE);
-    printf("  need to allocate %u bytes \n\n", names_list_len);
+      if (crypt_list_all_constants(NULL, &names_list_len) != 0) exit(EXIT_FAILURE);
+      printf("  need to allocate %u bytes \n\n", names_list_len);
 
-    /* get and print the names (and values) list */
-    if ((names_list = malloc(names_list_len)) == NULL)
-      exit(EXIT_FAILURE);
-    if (crypt_list_all_constants(names_list, &names_list_len) != 0)
-      exit(EXIT_FAILURE);
-    printf("  supported constants:\n\n%s\n\n", names_list);
-    free(names_list);
+      /* get and print the names (and values) list */
+      if ((names_list = malloc(names_list_len)) == NULL) exit(EXIT_FAILURE);
+      if (crypt_list_all_constants(names_list, &names_list_len) != 0) exit(EXIT_FAILURE);
+      printf("  supported constants:\n\n%s\n\n", names_list);
+      free(names_list);
+   } else if (argc == 2) {
+      if (strcmp(argv[1], "-h") == 0 || strcmp(argv[1], "--help") == 0) {
+         char* base = strdup(basename(argv[0]));
+         printf("Usage: %s [-a] [-s name]\n\n", base);
+         _print_line("<no argument>", "The old behavior of the demo");
+         _print_line("-a", "Only lists all constants");
+         _print_line("-s name", "List a single constant given as argument");
+         _print_line("-h", "The help you're looking at");
+         free(base);
+      } else if (strcmp(argv[1], "-a") == 0) {
+         char *names_list;
+         unsigned int names_list_len;
+         /* get and print the length of the names (and values) list */
+         if (crypt_list_all_constants(NULL, &names_list_len) != 0) exit(EXIT_FAILURE);
+         /* get and print the names (and values) list */
+         names_list = malloc(names_list_len);
+         if (crypt_list_all_constants(names_list, &names_list_len) != 0) exit(EXIT_FAILURE);
+         printf("%s\n", names_list);
+      }
+   } else if (argc == 3) {
+      if (strcmp(argv[1], "-s") == 0) {
+         int value;
+         if (crypt_get_constant(argv[2], &value) != 0) exit(EXIT_FAILURE);
+         printf("%s,%u\n", argv[2], value);
+      }
+   }
 
-    return 0;
+   return 0;
 }