Implement the --inplace flag.

cli.js

@@ -151,7 +151,15 @@ mainOptionKeys.forEach(function(key) {
     program.option('--' + paramCase(key), option);
   }
 });
-program.option('-o --output <file>', 'Specify output file (if not specified STDOUT will be used for output)');
+var inplace = false;
+program.option('--inplace', 'Specify that the files should be overwritten.', function(newInplace) {
+  inplace = newInplace;
+});
+program.option('-o --output <file>', 'Specify output file (if not specified STDOUT will be used for output)', function(outputPath) {
+  return fs.createWriteStream(outputPath).on('error', function(e) {
+    fatal('Cannot write ' + outputPath + '\n' + e.message);
+  });
+}, process.stdout);
 
 function readFile(file) {
   try {
@@ -190,8 +198,9 @@ program.option('--input-dir <dir>', 'Specify an input directory');
 program.option('--output-dir <dir>', 'Specify an output directory');
 program.option('--file-ext <text>', 'Specify an extension to be read, ex: html');
 var content;
-program.arguments('[files...]').action(function(files) {
-  content = files.map(readFile).join('');
+var files;
+program.arguments('[files...]').action(function(newFiles) {
+  files = newFiles;
 }).parse(process.argv);
 
 function createOptions() {
@@ -287,24 +296,34 @@ function writeMinify() {
 var inputDir = program.inputDir;
 var outputDir = program.outputDir;
 var fileExt = program.fileExt;
-if (inputDir || outputDir) {
-  if (!inputDir) {
-    fatal('The option output-dir needs to be used with the option input-dir. If you are working with a single file, use -o.');
-  }
-  else if (!outputDir) {
-    fatal('You need to specify where to write the output files with the option --output-dir');
-  }
-  processDirectory(inputDir, outputDir, fileExt);
-}
-// Minifying one or more files specified on the CMD line
-else if (content) {
-  writeMinify();
+if (inplace) {
+  files.forEach(function(file) {
+    processFile(file, file);
+  });
 }
-// Minifying input coming from STDIN
 else {
-  content = '';
-  process.stdin.setEncoding('utf8');
-  process.stdin.on('data', function(data) {
-    content += data;
-  }).on('end', writeMinify);
+  if (files) {
+    content = files.map(readFile).join('');
+  }
+  if (inputDir || outputDir) {
+    if (!inputDir) {
+      fatal('The option output-dir needs to be used with the option input-dir. If you are working with a single file, use -o.');
+    }
+    else if (!outputDir) {
+      fatal('You need to specify where to write the output files with the option --output-dir');
+    }
+    processDirectory(inputDir, outputDir, fileExt);
+  }
+  // Minifying one or more files specified on the CMD line
+  else if (typeof content === 'string') {
+    writeMinify();
+  }
+  // Minifying input coming from STDIN
+  else {
+    content = '';
+    process.stdin.setEncoding('utf8');
+    process.stdin.on('data', function(data) {
+      content += data;
+    }).on('end', writeMinify);
+  }
 }

test-cli.js

@@ -0,0 +1,53 @@
+#!/usr/bin/env node
+/**
+ * tests for the html-minifier CLI tool
+ *
+ * The MIT/Expat License (MIT)
+ *
+ *  Copyright (c) 2017 Shlomi Fish
+ *
+ *  Permission is hereby granted, free of charge, to any person obtaining a copy of
+ *  this software and associated documentation files (the "Software"), to deal in
+ *  the Software without restriction, including without limitation the rights to
+ *  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ *  the Software, and to permit persons to whom the Software is furnished to do so,
+ *  subject to the following conditions:
+ *
+ *  The above copyright notice and this permission notice shall be included in all
+ *  copies or substantial portions of the Software.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ *  FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ *  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ *  IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ *  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+'use strict';
+
+QUnit.module("CLI Tests");
+
+QUnit.test("inplace test", function(assert) {
+    assert.expect(2);
+
+    const fs = require('fs');
+
+    const temp_dir = fs.mkdtempSync('html-minifier-tests');
+    const fn1 = temp_dir + "/" + "foo.html";
+    const fn2 = temp_dir + "/" + "bar.html";
+    fs.writeFileSync(fn1, "<!DOCTYPE html>\n<html>\n<head>\n<meta charset=\"utf-8\">\n<title>Test file</title>\n</head>\n<body>\n    <p>Text</p>\n</body>\n</html>\n");
+    fs.writeFileSync(fn2, "<!DOCTYPE html>\n<html>\n<head>\n<meta charset=\"utf-8\">\n<title>Bar file</title>\n</head>\n<body>\n    <p>BarText</p>\n</body>\n</html>\n");
+
+    const execFileSync = require('child_process').execFileSync;
+    execFileSync('node', ['cli.js', '-c', 'sample-cli-config-file.conf', '--inplace', fn1, fn2]);
+
+    const contents1 = fs.readFileSync(fn1, {encoding: 'utf-8'});
+    const contents2 = fs.readFileSync(fn2, {encoding: 'utf-8'});
+
+    assert.equal (contents1, "<!DOCTYPE html><meta charset=utf-8><title>Test file</title><p>Text",
+    "file was modified in-place");
+    assert.equal (contents2, "<!DOCTYPE html><meta charset=utf-8><title>Bar file</title><p>BarText",
+    "second file was modified in-place");
+});

tests/index.html

@@ -3,14 +3,14 @@
   <head>
     <meta charset="utf-8">
     <title>HTML Minifier Tests</title>
-    <link rel="stylesheet" href="https://code.jquery.com/qunit/qunit-2.6.1.css">
+    <link rel="stylesheet" href="https://code.jquery.com/qunit/qunit-2.6.2.css">
   </head>
   <body>
     <div id="qunit">
       <button onclick="QUnit.start()">Start</button>
     </div>
     <div id="qunit-fixture"></div>
-    <script src="https://code.jquery.com/qunit/qunit-2.6.1.js"></script>
+    <script src="https://code.jquery.com/qunit/qunit-2.6.2.js"></script>
     <script src="../dist/htmlminifier.min.js"></script>
     <script src="minifier.js"></script>
   </body>