diff --git a/runner.c b/runner.c
index e69de29..eee0d2b 100644
--- a/runner.c
+++ b/runner.c
@@ -0,0 +1,26 @@
+#include runner.h
+
+int main(int argc, char *argv[]) {
+    char *check_input;
+
+    //check_input can be compared to INVALID_ARG and DIFF_ARG to determine if -tok and holds the generated file name if it is
+    check_input = is_tok(argc, argv);
+
+    return 0; //not sure what to do yet
+}
+
+char *is_tok(int argc, char *argv[]) {
+    if (argc == 3 && strcmp("-tok", argv[1])) {
+        char *input_prog = argv[2];
+        int file_len = strlen(input);
+        //check that input program is a .alpha file
+        if (strcmp(".alpha", input_prog[file_len - ALPHA_OFFSET]) != 0) {
+            return INVALID_ARG;
+        }
+        char *FILE_tok[file_len - ALPHA_OFFSET + TOK_LEN]; 
+        strncpy(input, FILE_tok, file_len - ALPHA_OFFSET); //copy name of prog before .alpha
+        strcpy(".tok", FILE_tok[file_len - ALPHA_OFFSET]); //add .tok to end of file name
+        return FILE_tok;
+    }
+    return DIFF_ARG;
+} 
diff --git a/runner.h b/runner.h
new file mode 100644
index 0000000..dff315f
--- /dev/null
+++ b/runner.h
@@ -0,0 +1,8 @@
+#define ALPHA_OFFSET 5
+#define TOK_LEN 3
+#define INVALID_ARG "invalid"
+#define DIFF_ARG "diff"
+#include <string.h>
+
+int main(int argc, char* argv);
+char *is_tok(int argc, char* argv);