Issue #654 working on adding feature fs.watchFile()

src/filesystem/interface.js

@@ -206,6 +206,50 @@ function FileSystem(options, callback) {
     return watcher;
   };
 
+  //Object that uses filenames as keys
+  const statWatchers = new Map(); 
+
+  this.watchFile = function(filename, options, listener) {
+    let prevStat, currStat; 
+
+    if (Path.isNull(filename)) {
+      throw new Error('Path must be a string without null bytes.');
+    }
+    // Checks to see if there were options passed in and if not, the callback function will be set here
+    if (typeof options === 'function') {
+      listener = options; 
+      options = {};
+    }
+    // default 5007ms interval, persistent is not used this project
+    const interval = options.interval || 5007;
+    listener = listener || nop;
+
+    // Stores initial prev value to compare 
+    fs.stat(filename, function(err, stats) { 
+      prevStat = stats;
+
+      // Stores interval return values
+      statWatchers.set(filename, value);
+
+      var value = setInterval(function() {
+        fs.stat(filename, function(err, stats) {
+          if(err) {
+            console.log(err);
+          }
+          // Store the current stat
+          currStat = stats;
+          if(Object.toJSON(prevStat) !== Object.toJSON(currStat)) { 
+            listener(prevStat, currStat);
+          }
+          // Set a new prevStat based on previous
+          prevStat = currStat;
+        });
+      }, 
+      interval
+      );
+    }); 
+  };
+
   // Deal with various approaches to node ID creation
   function wrappedGuidFn(context) {
     return function (callback) {

tests/index.js

@@ -41,6 +41,7 @@ require('./spec/trailing-slashes.spec');
 require('./spec/times.spec');
 require('./spec/time-flags.spec');
 require('./spec/fs.watch.spec');
+require('./spec/fs.watchFile.spec');
 require('./spec/fs.unwatchFile.spec');
 require('./spec/errors.spec');
 require('./spec/fs.shell.spec');

tests/spec/fs.watchFile.spec.js

@@ -0,0 +1,31 @@
+'use strict';
+
+var util = require('../lib/test-utils.js');
+var expect = require('chai').expect;
+
+describe('fs.watchFile', function() {
+  beforeEach(util.setup);
+  afterEach(util.cleanup);
+
+  it('should be a function', function() {
+    var fs = util.fs();
+    expect(typeof fs.watchFile).to.equal('function');
+  });
+
+  /*
+  it('should get a change event when writing a file', function(done) {
+    const fs = util.fs();
+
+    fs.watchFile('/myfile.txt', function(event, filename) {
+      expect(event).to.equal('change');
+      expect(filename).to.equal('/myfile.txt');
+      watcher.close();
+      done();
+    });
+
+    fs.writeFile('/myfile.txt', 'data', function(error) {
+      if(error) throw error;
+    });
+  });
+  */
+});