diff --git a/CMakeLists.txt b/CMakeLists.txt
index 36a96c2..7b34f76 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3,4 +3,4 @@ project(passwdgen)
 
 set(CMAKE_CXX_STANDARD 20)
 
-add_executable(passwdgen main.cpp)
\ No newline at end of file
+add_executable(passwdgen passwdgen.cpp)
\ No newline at end of file
diff --git a/main.cpp b/passwdgen.cpp
similarity index 65%
rename from main.cpp
rename to passwdgen.cpp
index 582b899..b06b512 100644
--- a/main.cpp
+++ b/passwdgen.cpp
@@ -1,6 +1,12 @@
+//
+//  passwdgen.cpp
+//  Created by Greg Gauthier on 2020.10.22.
+//
+
 #include <iostream>
 #include <random>
 
+
 std::string random_string(std::size_t length, bool punc) {
     std::string CHARACTERS;
     std::string ALPHANUM = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
@@ -13,7 +19,7 @@ std::string random_string(std::size_t length, bool punc) {
     }
     std::random_device random_device;
     std::mt19937 generator(random_device());
-    std::uniform_int_distribution<> distribution(0, CHARACTERS.size() - 1);
+    std::uniform_int_distribution<> distribution(0.0, CHARACTERS.size() - 1.0);
 
     std::string random_string;
     for (std::size_t i = 0; i < length; ++i) {
@@ -25,15 +31,15 @@ std::string random_string(std::size_t length, bool punc) {
 void show_usage(std::string binname) {
     std::cerr << "Usage: " << binname << " [OPTIONS] " << std::endl
               << "Options:" << std::endl
-              << "\t-h, --help        \t\tShow this help message" << std::endl
-              << "\t-l, --length      \t\tThe length of the password (default: 32)" << std::endl
+              << "\t-h, --help          \t\tShow this help message" << std::endl
+              << "\t-l, --length [n]    \t\tThe length of the password (default: 32)" << std::endl
               << "\t-p, --punctuation \t\tToggle special characters (default: false)"
               << std::endl;
 }
 
 int main(int argc, char *argv[]) {
     std::string passlenstr;
-    int passlen;
+    int passlen = 0;
     bool punc = false;
 
     if (argc < 1) {
@@ -48,18 +54,24 @@ int main(int argc, char *argv[]) {
             } else if (arg == "-p") {
                 punc = true;
             } else if ((arg == "-l") || (arg == "--length")) {
-                passlenstr = argv[i + 1];
-                if (passlenstr.empty()) {
-                    std::cerr << "--destination option requires one argument." << std::endl;
+                if (not argv[i +1]) {
+                    std::cerr << "Specify a password length" << std::endl;
                     return 1;
+                } else {
+                    passlenstr = argv[i + 1];
+                    try {
+                        passlen = std::stoi(passlenstr);
+                    } catch (const std::invalid_argument& e){
+                        std::cerr << "Length must be a valid integer" << std::endl;
+                        return 1;
+                    }
                 }
             }
         }
 
-        if (passlenstr.empty()) {
-            passlenstr = "32";
+        if (passlen == 0) {
+            passlen = 32;
         }
-        passlen = std::stoi(passlenstr);
         std::string password = random_string(passlen, punc);
         std::cout << password << std::endl;
         return 0;