node.js fs.readdir recursive directory search

Question

Any ideas on an async directory search using fs.readdir? I realise that we could introduce recursion and call the read directory function with the next directory to read, bu

Answer 1

There are basically two ways of accomplishing this. In an async environment you'll notice that there are two kinds of loops: serial and parallel. A serial loop waits for one iteration to complete before it moves onto the next iteration - this guarantees that every iteration of the loop completes in order. In a parallel loop, all the iterations are started at the same time, and one may complete before another, however, it is much faster than a serial loop. So in this case, it's probably better to use a parallel loop because it doesn't matter what order the walk completes in, just as long as it completes and returns the results (unless you want them in order).

A parallel loop would look like this:

var fs = require('fs');
var path = require('path');
var walk = function(dir, done) {
  var results = [];
  fs.readdir(dir, function(err, list) {
    if (err) return done(err);
    var pending = list.length;
    if (!pending) return done(null, results);
    list.forEach(function(file) {
      file = path.resolve(dir, file);
      fs.stat(file, function(err, stat) {
        if (stat && stat.isDirectory()) {
          walk(file, function(err, res) {
            results = results.concat(res);
            if (!--pending) done(null, results);
          });
        } else {
          results.push(file);
          if (!--pending) done(null, results);
        }
      });
    });
  });
};

A serial loop would look like this:

var fs = require('fs');
var path = require('path');
var walk = function(dir, done) {
  var results = [];
  fs.readdir(dir, function(err, list) {
    if (err) return done(err);
    var i = 0;
    (function next() {
      var file = list[i++];
      if (!file) return done(null, results);
      file = path.resolve(dir, file);
      fs.stat(file, function(err, stat) {
        if (stat && stat.isDirectory()) {
          walk(file, function(err, res) {
            results = results.concat(res);
            next();
          });
        } else {
          results.push(file);
          next();
        }
      });
    })();
  });
};

And to test it out on your home directory (WARNING: the results list will be huge if you have a lot of stuff in your home directory):

walk(process.env.HOME, function(err, results) {
  if (err) throw err;
  console.log(results);
});

EDIT: Improved examples.

Answer 2

I loved the answer from chjj above and would not have been able to create my version of the parallel loop without that start.

var fs = require("fs");

var tree = function(dir, done) {
  var results = {
        "path": dir
        ,"children": []
      };
  fs.readdir(dir, function(err, list) {
    if (err) { return done(err); }
    var pending = list.length;
    if (!pending) { return done(null, results); }
    list.forEach(function(file) {
      fs.stat(dir + '/' + file, function(err, stat) {
        if (stat && stat.isDirectory()) {
          tree(dir + '/' + file, function(err, res) {
            results.children.push(res);
            if (!--pending){ done(null, results); }
          });
        } else {
          results.children.push({"path": dir + "/" + file});
          if (!--pending) { done(null, results); }
        }
      });
    });
  });
};

module.exports = tree;

I created a Gist as well. Comments welcome. I am still starting out in the NodeJS realm so that is one way I hope to learn more.

Answer 3

A. Have a look at the file module. It has a function called walk:

file.walk(start, callback)

Navigates a file tree, calling callback for each directory, passing in (null, dirPath, dirs, files).

This may be for you! And yes, it is async. However, I think you would have to aggregate the full path's yourself, if you needed them.

B. An alternative, and even one of my favourites: use the unix find for that. Why do something again, that has already been programmed? Maybe not exactly what you need, but still worth checking out:

var execFile = require('child_process').execFile;
execFile('find', [ 'somepath/' ], function(err, stdout, stderr) {
  var file_list = stdout.split('\n');
  /* now you've got a list with full path file names */
});

Find has a nice build-in caching mechanism that makes subsequent searches very fast, as long as only few folder have changed.

Answer 4

Using Promises (Q) to solve this in a Functional style:

var fs = require('fs'),
    fsPath = require('path'),
    Q = require('q');

var walk = function (dir) {
  return Q.ninvoke(fs, 'readdir', dir).then(function (files) {

    return Q.all(files.map(function (file) {

      file = fsPath.join(dir, file);
      return Q.ninvoke(fs, 'lstat', file).then(function (stat) {

        if (stat.isDirectory()) {
          return walk(file);
        } else {
          return [file];
        }
      });
    }));
  }).then(function (files) {
    return files.reduce(function (pre, cur) {
      return pre.concat(cur);
    });
  });
};

It returns a promise of an array, so you can use it as:

walk('/home/mypath').then(function (files) { console.log(files); });

Answer 5

Because everyone should write his own, I made one.

walk(dir, cb, endCb) cb(file) endCb(err | null)

DIRTY

module.exports = walk;

function walk(dir, cb, endCb) {
  var fs = require('fs');
  var path = require('path');

  fs.readdir(dir, function(err, files) {
    if (err) {
      return endCb(err);
    }

    var pending = files.length;
    if (pending === 0) {
      endCb(null);
    }
    files.forEach(function(file) {
      fs.stat(path.join(dir, file), function(err, stats) {
        if (err) {
          return endCb(err)
        }

        if (stats.isDirectory()) {
          walk(path.join(dir, file), cb, function() {
            pending--;
            if (pending === 0) {
              endCb(null);
            }
          });
        } else {
          cb(path.join(dir, file));
          pending--;
          if (pending === 0) {
            endCb(null);
          }
        }
      })
    });

  });
}

Answer 6

Using bluebird promise.coroutine:

let promise = require('bluebird'),
    PC = promise.coroutine,
    fs = promise.promisifyAll(require('fs'));
let getFiles = PC(function*(dir){
    let files = [];
    let contents = yield fs.readdirAsync(dir);
    for (let i = 0, l = contents.length; i < l; i ++) {
        //to remove dot(hidden) files on MAC
        if (/^\..*/.test(contents[i])) contents.splice(i, 1);
    }
    for (let i = 0, l = contents.length; i < l; i ++) {
        let content = path.resolve(dir, contents[i]);
        let contentStat = yield fs.statAsync(content);
        if (contentStat && contentStat.isDirectory()) {
            let subFiles = yield getFiles(content);
            files = files.concat(subFiles);
        } else {
            files.push(content);
        }
    }
    return files;
});
//how to use
//easy error handling in one place
getFiles(your_dir).then(console.log).catch(err => console.log(err));