diff --git a/index.js b/index.js
index 24abaa1..44fd9bc 100644
--- a/index.js
+++ b/index.js
@@ -3,65 +3,83 @@
 const request = require("request");
 const path = require("path");
 const colors = require("colors");
-const fs = require("fs");
-const regex = /(http(s)?:\/\/.)?(www\.)?[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]{2,6}\b([-a-zA-Z0-9@:%_\+.~#?&//=]*)/g
+const fs = require("fs").promises;
+const regex = /(http(s)?:\/\/.)?(www\.)?[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]{2,6}\b([-a-zA-Z0-9@:%_\+.~#?&//=]*)/g;
 
 // If the user doesn't enter any arguments/filenames, it exits the process
 if (process.argv.length === 2) {
-    console.log("Usage: url-fi [argument(s)] [FILENAME]")
-    console.log("-v: print the tool name and its version")
-    console.log("-s: check whether http:// work using https://")
-    console.log("-h: display the usage of this tool")
-    process.exit(1)
+  console.log("Usage: url-fi [argument(s)] [FILENAME]");
+  console.log("-v: print the tool name and its version");
+  console.log("-s: check whether http:// work using https://");
+  console.log("-h: display the usage of this tool");
 }
 
 // for option -s, -h, and -v
 // If user enter -s, the program checks whether http:// actually work using https://
 // If user enter -h, the program prints out the usage of this tool
 let sFlag = false;
+let files = [];
 for (let i = 2; i < process.argv.length; i++) {
-    let arg = process.argv[i];
-    if (arg.startsWith('-')) {
-        if (arg.includes("s")) {
-            sFlag = true;
-        }
+  let arg = process.argv[i];
+  if (arg.startsWith("-")) {
+    if (arg.includes("s")) {
+      sFlag = true;
+    }
 
-        if (arg.includes("h")) {
-            console.log("Usage: url-fi [FILENAME]")
-        }
+    if (arg.includes("h")) {
+      console.log("Usage: url-fi [FILENAME]");
+    }
 
-        if (arg.includes("v")) {
-            console.log("Tool Name: url-fi")
-            console.log("Version: 0.1")
-        }
+    if (arg.includes("v")) {
+      console.log("Tool Name: url-fi");
+      console.log("Version: 0.1");
     }
+  } else {
+    if (checkFile(arg)) files.push(arg);
+  }
+}
+
+// Aggregates links from one or multiple files
+async function readArgFile() {
+  try {
+    console.log(colors.cyan(`${files.length} file/s found`));
+    let data;
+    for (let file of files) {
+      data += await fs.readFile(file, "utf8");
+    }
+    return data;
+  } catch (err) {
+    console.error(err);
+  }
 }
 
 // If the user enters any arguments/filenames, starts process.
 // --version or -v: prints tool name & version
 // filename: checks broken links
-for (let i = 2; i < process.argv.length; i++) {
-    let arg = process.argv[i];
-    if (!arg.startsWith("-")) {
-        fs.readFile(path.normalize(arg), 'utf8', function (err, data) {
-            if (err) {
-                console.log(colors.red(err));
-                process.exit(1);
-            }
-            let links = data.match(regex);
-            for (let i = 0; i < links.length; i++) {
-                let link = links[i];
-                if (link.startsWith("https://")) {
-                    checkUrl(link);
-                } else {
-                    checkUrl(link);
-                    if (sFlag) {
-                        checkUrl(link.replace(/^http/, "https"));
-                    }
-                }
-            }
-        })
-    }
+async function sendHeadRequests(uList) {
+  let urlList = uList.toString();
+  urlList = urlList.match(regex);
+  console.log(colors.cyan(`${urlList.length} links collected`));
+
+  if (sFlag) {
+    urlList = urlList.map((links) => {
+      return links.replace(/^http/, "https");
+    });
+    console.log(colors.magenta("Testing http links with https"));
+  }
+
+  for (link of urlList) {
+    checkUrl(link);
+  }
+}
+
+// Main sequence
+if (files.length > 0) {
+  readArgFile()
+    .then((data) => sendHeadRequests(data))
+    .catch((err) => {
+      console.error(err);
+    });
 }
 
 // Checks the link is broken or not
@@ -69,15 +87,25 @@ for (let i = 2; i < process.argv.length; i++) {
 // - status code 400, 404: broken
 // - otherwise: unknown
 function checkUrl(url) {
-    request({ method: 'HEAD', uri: url }, function (err, res, body) {
-        if (err) {
-            console.log(colors.yellow(`${err} ${url}`));
-        } else if (res.statusCode == 200) {
-            console.log(colors.green(`[PASSED] [200] ${url}`));
-        } else if (res.statusCode == 404 || res.statusCode == 400) {
-            console.log(colors.red(`[FAILED] [${res.statusCode}] ${url}`));
-        } else {
-            console.log(colors.grey(`[UNKNOWN] [${res.statusCode}] ${url}`))
-        }
-    })
+  request({ method: "HEAD", uri: url }, function (err, res, body) {
+    if (err) {
+      console.log(colors.yellow(`${err} ${url}`));
+    } else if (res.statusCode == 200) {
+      console.log(colors.green(`[PASSED] [200] ${url}`));
+    } else if (res.statusCode == 404 || res.statusCode == 400) {
+      console.log(colors.red(`[FAILED] [${res.statusCode}] ${url}`));
+    } else {
+      console.log(colors.grey(`[UNKNOWN] [${res.statusCode}] ${url}`));
+    }
+  });
+}
+
+// Checks if argument provided is a file
+async function checkFile(arg) {
+  try {
+    const stat = await fs.lstat(arg);
+    return stat.isFile();
+  } catch (err) {
+    console.error(err);
+  }
 }