walk/README.md

# 2021 Update

Consider using [`@root/walk`](https://npmjs.org/package/@root/walk) instead.

I created `walk` quite literally a decade ago, in the Node v0.x days.
Back then using an EventEmitter seemed like the thing to do. Nowadays,
it seems a bit overkill for the simple task of walking over directories.

There's nothing wrong with `walk` - it's about the same as it was 10 years ago -
however, at only 50 lines of code long, `@root/walk` is much simpler and much faster.

# node-walk

| a [Root](https://rootprojects.org) project

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

```bash
npm install --save walk
```

# Getting Started

```javascript
'use strict';

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

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:

```javascript
{ 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.

```javascript
'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.

```javascript
(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 `stat`ed

- `names` - before any `stat` takes place. Useful for sorting and filtering.

  - Note: the array is an array of `string`s, 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

Copyright 2011 - Present AJ ONeal