* `path` {string|Buffer}

* `mode` {integer}

* `callback` {Function}

* `err` {Error}

Tests a user's permissions for the file or directory specified by `path`.

The `mode` argument is an optional integer that specifies the accessibility

* `mode` {integer} default = `0o666`

* `flag` {string} default = `'a'`

* `callback` {Function}

* `err` {Error}

Asynchronously append data to a file, creating the file if it does not yet exist.

`data` can be a string or a buffer.

* `path` {string|Buffer}

* `mode` {integer}

* `callback` {Function}

* `err` {Error}

Asynchronous chmod(2). No arguments other than a possible exception are given

to the completion callback.

* `uid` {integer}

* `gid` {integer}

* `callback` {Function}

* `err` {Error}

Asynchronous chown(2). No arguments other than a possible exception are given

to the completion callback.

* `fd` {integer}

* `callback` {Function}

* `err` {Error}

Asynchronous close(2). No arguments other than a possible exception are given

to the completion callback.

* `path` {string|Buffer}

* `callback` {Function}

* `exists` {Boolean}

Test whether or not the given path exists by checking with the file system.

Then call the `callback` argument with either true or false. Example:

* `fd` {integer}

* `mode` {integer}

* `callback` {Function}

* `err` {Error}

Asynchronous fchmod(2). No arguments other than a possible exception

are given to the completion callback.

* `uid` {integer}

* `gid` {integer}

* `callback` {Function}

* `err` {Error}

Asynchronous fchown(2). No arguments other than a possible exception are given

to the completion callback.

* `fd` {integer}

* `callback` {Function}

* `err` {Error}

Asynchronous fdatasync(2). No arguments other than a possible exception are

given to the completion callback.

* `fd` {integer}

* `callback` {Function}

* `err` {Error}

* `stats` {fs.Stats}

Asynchronous fstat(2). The callback gets two arguments `(err, stats)` where

`stats` is an [`fs.Stats`][] object. `fstat()` is identical to [`stat()`][],

* `fd` {integer}

* `callback` {Function}

* `err` {Error}

Asynchronous fsync(2). No arguments other than a possible exception are given

to the completion callback.

* `fd` {integer}

* `len` {integer} default = `0`

* `callback` {Function}

* `err` {Error}

Asynchronous ftruncate(2). No arguments other than a possible exception are

given to the completion callback.

* `atime` {integer}

* `mtime` {integer}

* `callback` {Function}

* `err` {Error}

Change the file timestamps of a file referenced by the supplied file

descriptor.

* `path` {string|Buffer}

* `mode` {integer}

* `callback` {Function}

* `err` {Error}

Asynchronous lchmod(2). No arguments other than a possible exception

are given to the completion callback.

* `uid` {integer}

* `gid` {integer}

* `callback` {Function}

* `err` {Error}

Asynchronous lchown(2). No arguments other than a possible exception are given

to the completion callback.

* `existingPath` {string|Buffer}

* `newPath` {string|Buffer}

* `callback` {Function}

* `err` {Error}

Asynchronous link(2). No arguments other than a possible exception are given to

the completion callback.

* `path` {string|Buffer}

* `callback` {Function}

* `err` {Error}

* `stats` {fs.Stats}

Asynchronous lstat(2). The callback gets two arguments `(err, stats)` where

`stats` is a [`fs.Stats`][] object. `lstat()` is identical to `stat()`,

* `path` {string|Buffer}

* `mode` {integer}

* `callback` {Function}

* `err` {Error}

Asynchronous mkdir(2). No arguments other than a possible exception are given

to the completion callback. `mode` defaults to `0o777`.

* `options` {string|Object}

* `encoding` {string} default = `'utf8'`

* `callback` {Function}

* `err` {Error}

* `folder` {string}

Creates a unique temporary directory.

* `flags` {string|number}

* `mode` {integer}

* `callback` {Function}

* `err` {Error}

* `fd` {integer}

Asynchronous file open. See open(2). `flags` can be:

* `length` {integer}

* `position` {integer}

* `callback` {Function}

* `err` {Error}

* `bytesRead` {integer}

* `buffer` {Buffer}

Read data from the file specified by `fd`.

* `options` {string|Object}

* `encoding` {string} default = `'utf8'`

* `callback` {Function}

* `err` {Error}

* `files` {string[]|Buffer[]}

Asynchronous readdir(3). Reads the contents of a directory.

The callback gets two arguments `(err, files)` where `files` is an array of

* `encoding` {string|null} default = `null`

* `flag` {string} default = `'r'`

* `callback` {Function}

* `err` {Error}

* `data` {string|Buffer}

Asynchronously reads the entire contents of a file. Example:

* `options` {string|Object}

* `encoding` {string} default = `'utf8'`

* `callback` {Function}

* `err` {Error}

* `linkString` {string|Buffer}

Asynchronous readlink(2). The callback gets two arguments `(err,

linkString)`.

* `options` {string|Object}

* `encoding` {string} default = `'utf8'`

* `callback` {Function}

* `err` {Error}

* `resolvedPath` {string|Buffer}

Asynchronous realpath(3). The `callback` gets two arguments `(err,

resolvedPath)`. May use `process.cwd` to resolve relative paths.

* `oldPath` {string|Buffer}

* `newPath` {string|Buffer}

* `callback` {Function}

* `err` {Error}

Asynchronous rename(2). No arguments other than a possible exception are given

to the completion callback.

* `path` {string|Buffer}

* `callback` {Function}

* `err` {Error}

Asynchronous rmdir(2). No arguments other than a possible exception are given

to the completion callback.

* `path` {string|Buffer}

* `callback` {Function}

* `err` {Error}

* `stats` {fs.Stats}

Asynchronous stat(2). The callback gets two arguments `(err, stats)` where

`stats` is an [`fs.Stats`][] object.

* `path` {string|Buffer}

* `type` {string}

* `callback` {Function}

* `err` {Error}

Asynchronous symlink(2). No arguments other than a possible exception are given

to the completion callback. The `type` argument can be set to `'dir'`,

* `path` {string|Buffer}

* `len` {integer} default = `0`

* `callback` {Function}

* `err` {Error}

Asynchronous truncate(2). No arguments other than a possible exception are

given to the completion callback. A file descriptor can also be passed as the

* `path` {string|Buffer}

* `callback` {Function}

* `err` {Error}

Asynchronous unlink(2). No arguments other than a possible exception are given

to the completion callback.

* `filename` {string|Buffer}

* `listener` {Function}

* `eventType` {string}

* `filename` {string|Buffer}

Stop watching for changes on `filename`. If `listener` is specified, only that

particular listener is removed. Otherwise, *all* listeners are removed and you

* `atime` {integer}

* `mtime` {integer}

* `callback` {Function}

* `err` {Error}

Change file timestamps of the file referenced by the supplied path.

* `encoding` {string} Specifies the character encoding to be used for the

filename passed to the listener. default = `'utf8'`

* `listener` {Function}

* `eventType` {string}

* `filename` {string|Buffer}

Watch for changes on `filename`, where `filename` is either a file or a

directory. The returned object is a [`fs.FSWatcher`][].

* `persistent` {boolean}

* `interval` {integer}

* `listener` {Function}

* `current` {fs.Stats}

* `previous` {fs.Stats}

Watch for changes on `filename`. The callback `listener` will be called each

time the file is accessed.

* `length` {integer}

* `position` {integer}

* `callback` {Function}

* `err` {Error}

* `bytesWritten` {integer}

* `buffer` {Buffer|Uint8Array}

Write `buffer` to the file specified by `fd`.

* `position` {integer}

* `encoding` {string}

* `callback` {Function}

* `err` {Error}

* `written` {integer}

* `string` {string}

Write `string` to the file specified by `fd`. If `string` is not a string, then

the value will be coerced to one.

* `mode` {integer} default = `0o666`

* `flag` {string} default = `'w'`

* `callback` {Function}

* `err` {Error}

Asynchronously writes data to a file, replacing the file if it already exists.

`data` can be a string or a buffer.