enter shows timestamp when enter is pressed

Author: alanboy

tail.js

@@ -1,65 +1,77 @@
 const fs = require('fs');
 const readline = require('readline');
 
-// Define the filename and number of lines
-const filename = process.argv[2];
-const numLines = parseInt(process.argv[3]) || 10;
+// Parse command line arguments
+const args = process.argv.slice(2);
+let numLines = 10; // default number of lines
+let filePath = null;
 
-if (!filename) {
-  console.error('Usage: node tail.js <filename> [number of lines]');
-  process.exit(1);
+for (let i = 0; i < args.length; i++) {
+    if (args[i] === '-n' && i + 1 < args.length) {
+        numLines = parseInt(args[i + 1]);
+        i++; // skip the next argument since we used it
+    } else if (!filePath) {
+        filePath = args[i];
+    }
 }
 
-// Function to read the last N lines
-function readLastLines(file, numLines) {
-  return new Promise((resolve, reject) => {
-    const lines = [];
-    const stream = fs.createReadStream(file, { encoding: 'utf8' });
-    const rl = readline.createInterface({ input: stream });
+if (!filePath) {
+    console.error('Usage: node tail.js <filename> [-n lines]');
+    process.exit(1);
+}
 
-    rl.on('line', (line) => {
-      lines.push(line);
-      if (lines.length > numLines) {
-        lines.shift();
-      }
-    });
+// Create interface for stdin/stdout
+const rl = readline.createInterface({
+    input: process.stdin,
+    output: process.stdout
+});
 
-    rl.on('close', () => resolve(lines));
-    rl.on('error', reject);
-  });
+// ANSI escape codes for red background and reset
+const RED_BG = '\x1b[41m';
+const RESET = '\x1b[0m';
+
+// Function to read last N lines of a file
+function readLastLines(file, n) {
+    try {
+        const content = fs.readFileSync(file, 'utf8');
+        const lines = content.split('\n');
+        return lines.slice(-n).join('\n');
+    } catch (err) {
+        console.error(`Error reading file: ${err.message}`);
+        process.exit(1);
+    }
 }
 
-// Function to follow the file
+// Function to follow file changes
 function followFile(file) {
-  let fileSize = fs.statSync(file).size;
+    let fileSize = fs.statSync(file).size;
 
-  fs.watch(file, (eventType) => {
-    if (eventType === 'change') {
-      const newFileSize = fs.statSync(file).size;
-      if (newFileSize > fileSize) {
-        const stream = fs.createReadStream(file, {
-          encoding: 'utf8',
-          start: fileSize,
-        });
-
-        stream.on('data', (chunk) => {
-          process.stdout.write(chunk);
-        });
-
-        fileSize = newFileSize;
-      }
-    }
-  });
+    fs.watch(file, (eventType) => {
+        if (eventType === 'change') {
+            const newSize = fs.statSync(file).size;
+            if (newSize > fileSize) {
+                const stream = fs.createReadStream(file, {
+                    start: fileSize,
+                    encoding: 'utf8'
+                });
+                stream.on('data', (chunk) => process.stdout.write(chunk));
+                fileSize = newSize;
+            }
+        }
+    });
 }
 
-// Read the last few lines and start following the file
-readLastLines(filename, numLines)
-  .then((lines) => {
-    console.log(lines.join('\n'));
-    console.log('\n--- Start Following File ---');
-    followFile(filename);
-  })
-  .catch((err) => {
-    console.error(`Error: ${err.message}`);
-  });
+// Show initial lines
+console.log(`Last ${numLines} lines of ${filePath}:`);
+console.log(readLastLines(filePath, numLines));
+console.log('\n--- Following file (Press Enter for timestamp, Ctrl+C to exit) ---');
+
+// Start following the file
+followFile(filePath);
 
+// Listen for Enter key press
+rl.on('line', () => {
+    const now = new Date();
+    const timestamp = now.toISOString();
+    console.log(`${RED_BG}${timestamp}${RESET}`);
+});