Add error handling for non-numbers passedHEADmaster

Non-numbers that are passed will return -1, and print an error message.
This includes decimal places, as only integers can be even or odd.

1 files changed, 6 insertions, 2 deletions

diff --git a/src/main.c b/src/main.c
index e415020..ac45fd5 100644
--- a/src/main.c
+++ b/src/main.c
@@ -35,7 +35,7 @@ int main(int argc, char **argv) {
   quiet = false;
   value = false;
   result = 0;
-  char *output;
+  char *end = NULL;
 
   if (argc > 1) {
     for (int i = 1; i < argc; i++) {
@@ -55,7 +55,11 @@ int main(int argc, char **argv) {
             break;
         }
       }
-      result = strtol(argv[i], &output, 10);
+      result = strtol(argv[i], &end, 10);
+      if ((end == argv[i]) || (end[0] != '\0')) {
+        fprintf(stderr, "Please provide an integer, not %s!\n", argv[i]);
+        return ERR;
+      }
       value = true;
     }
   } else {