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node-walk

| Sponsored by ppl

nodejs walk implementation.

This is somewhat of a port python's os.walk, but using Node.JS conventions.

EventEmitter
Asynchronous
Chronological (optionally)
Built-in flow-control
includes Synchronous version (same API as Asynchronous)

As few file descriptors are opened at a time as possible. This is particularly well suited for single hard disks which are not flash or solid state.

Installation

npm install --save walk

Getting Started

(function () {
  "use strict";

  var walk = require('walk');
  var fs = require('fs');
  var walker;

  walker = walk.walk("/tmp", options);

  walker.on("file", function (root, fileStats, next) {
    fs.readFile(fileStats.name, function () {
      // doStuff
      next();
    });
  });

  walker.on("errors", function (root, nodeStatsArray, next) {
    next();
  });

  walker.on("end", function () {
    console.log("all done");
  });
}());

Common Events

All single event callbacks are in the form of function (root, stat, next) {}.

All multiple event callbacks callbacks are in the form of function (root, stats, next) {}, except names which is an array of strings.

All error event callbacks are in the form function (root, stat/stats, next) {}. stat.error contains the error.

names
directory
directories
file
files
end
nodeError (stat failed)
directoryError (stat succedded, but readdir failed)
errors (a collection of any errors encountered)

A typical stat event looks like this:

{ dev: 16777223,
  mode: 33188,
  nlink: 1,
  uid: 501,
  gid: 20,
  rdev: 0,
  blksize: 4096,
  ino: 49868100,
  size: 5617,
  blocks: 16,
  atime: Mon Jan 05 2015 18:18:10 GMT-0700 (MST),
  mtime: Thu Sep 25 2014 21:21:28 GMT-0600 (MDT),
  ctime: Thu Sep 25 2014 21:21:28 GMT-0600 (MDT),
  birthtime: Thu Sep 25 2014 21:21:28 GMT-0600 (MDT),
  name: 'README.md',
  type: 'file' }

Advanced Example

Both Asynchronous and Synchronous versions are provided.

(function () {
  "use strict";

  var walk = require('walk');
  var fs = require('fs');
  var options;
  var walker;

  options = {
    followLinks: false
    // directories with these keys will be skipped
  , filters: ["Temp", "_Temp"]
  };

  walker = walk.walk("/tmp", options);

  // OR
  // walker = walk.walkSync("/tmp", options);

  walker.on("names", function (root, nodeNamesArray) {
    nodeNamesArray.sort(function (a, b) {
      if (a > b) return 1;
      if (a < b) return -1;
      return 0;
    });
  });

  walker.on("directories", function (root, dirStatsArray, next) {
    // dirStatsArray is an array of `stat` objects with the additional attributes
    // * type
    // * error
    // * name

    next();
  });

  walker.on("file", function (root, fileStats, next) {
    fs.readFile(fileStats.name, function () {
      // doStuff
      next();
    });
  });

  walker.on("errors", function (root, nodeStatsArray, next) {
    next();
  });

  walker.on("end", function () {
    console.log("all done");
  });
}());

Sync

Note: You can't use EventEmitter if you want truly synchronous walker (although it's synchronous under the hood, it appears not to be due to the use of process.nextTick()).

Instead you must use options.listeners for truly synchronous walker.

Although the sync version uses all of the fs.readSync, fs.readdirSync, and other sync methods, I don't think I can prevent the process.nextTick() that EventEmitter calls.

(function () {
  "use strict";

  var walk = require('walk');
  var fs = require('fs');
  var options;
  var walker;

  // To be truly synchronous in the emitter and maintain a compatible api,
  // the listeners must be listed before the object is created
  options = {
    listeners: {
      names: function (root, nodeNamesArray) {
        nodeNamesArray.sort(function (a, b) {
          if (a > b) return 1;
          if (a < b) return -1;
          return 0;
        });
      }
    , directories: function (root, dirStatsArray, next) {
        // dirStatsArray is an array of `stat` objects with the additional attributes
        // * type
        // * error
        // * name

        next();
      }
    , file: function (root, fileStats, next) {
        fs.readFile(fileStats.name, function () {
          // doStuff
          next();
        });
      }
    , errors: function (root, nodeStatsArray, next) {
        next();
      }
    }
  };

  walker = walk.walkSync("/tmp", options);

  console.log("all done");
}());

API

Emitted Values

on('XYZ', function(root, stats, next) {})
root - the containing the files to be inspected
stats[Array] - a single stats object or an array with some added attributes
- type - 'file', 'directory', etc
- error
- name - the name of the file, dir, etc
next - no more files will be read until this is called

Single Events - fired immediately

end - No files, dirs, etc left to inspect
directoryError - Error when fstat succeeded, but reading path failed (Probably due to permissions).
nodeError - Error fstat did not succeeded.
node - a stats object for a node of any type
file - includes links when followLinks is true
directory - NOTE you could get a recursive loop if followLinks and a directory links to its parent
symbolicLink - always empty when followLinks is true
blockDevice
characterDevice
FIFO
socket

Events with Array Arguments - fired after all files in the dir have been stated

names - before any stat takes place. Useful for sorting and filtering.
- Note: the array is an array of strings, not stat objects
- Note: the next argument is a noop
errors - errors encountered by fs.stat when reading ndes in a directory
nodes - an array of stats of any type
files
directories - modification of this array - sorting, removing, etc - affects traversal
symbolicLinks
blockDevices
characterDevices
FIFOs
sockets

Warning beware of infinite loops when followLinks is true (using walk-recurse varient).

Comparisons

Tested on my /System containing 59,490 (+ self) directories (and lots of files). The size of the text output was 6mb.

find: time bash -c "find /System -type d | wc" 59491 97935 6262916

real  2m27.114s
user  0m1.193s
sys 0m14.859s

find.js:

Note that find.js omits the start directory

time bash -c "node examples/find.js /System -type d | wc"
59490   97934 6262908

# Test 1
real  2m52.273s
user  0m20.374s
sys 0m27.800s

# Test 2
real  2m23.725s
user  0m18.019s
sys 0m23.202s

# Test 3
real  2m50.077s
user  0m17.661s
sys 0m24.008s

In conclusion node.js asynchronous walk is much slower than regular "find".

LICENSE

node-walk is available under the following licenses:

MIT
Apache 2

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