fs-ext
======

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Extras not included in Node's fs module.

**Note**:

* From `v2.0.0` onwards, module doesn't override `fs` and `constants` Node.js core modules. Instead
  import functions and constants directly:

  ```js
  const {flock, constants} = require('fs-ext');
  // or
  const fsExt = require('fs-ext');
  // fsExt.flock
  // fsExt.constants
  ```

* From `v1.0.0` onwards, fs.utime and fs.utimeSync have been removed.
  Use fs.utimes and fs.utimesSync instead.

Installation
------------

Install via npm:

```sh
npm install fs-ext
```

Usage
-----

fs-ext imports all of the methods from the core 'fs' module, so you don't
need two objects.

```js
const fs = require('fs');
const {flock} = require('fs-ext');

const fd = fs.openSync('foo.txt', 'r');
flock(fd, 'ex', (err) => {
    if (err) {
        return console.error("Couldn't lock file");
    }
    // file is locked
});
```

For an advanced example checkout `example.js`.

API
---

### flock(fd, flags, [callback])

Asynchronous flock(2). No arguments other than a possible error are passed to
the callback. Flags can be 'sh', 'ex', 'shnb', 'exnb', 'un' and correspond
to the various LOCK_SH, LOCK_EX, LOCK_SH|LOCK_NB, etc.

NOTE (from flock() man page): flock() does not lock files over NFS. Use fcntl(2)
instead: that does work over NFS, given a sufficiently recent version of Linux
and a server which supports locking.


### flockSync(fd, flags)

Synchronous flock(2). Throws an exception on error.

### fcntl(fd, cmd, [arg], [callback])

Asynchronous fcntl(2).

callback will be given two arguments (err, result).

The supported commands are:

- 'getfd' ( F_GETFD )
- 'setfd' ( F_SETFD )
- 'setlk' ( F_SETLK )
- 'getlk' ( F_GETLK )
- 'setlkw' ( F_SETLKW )

Requiring this module adds `FD_CLOEXEC` to the constants module, for use with F_SETFD,
and also F_RDLCK, F_WRLCK and F_UNLCK for use with F_SETLK (etc).

File locking can be used like so:

```js
const {fnctl, constants} = require('fs-ext');

fcntl(fd, 'setlkw', constants.F_WRLCK, (err) => {
    if (!err) {
        // Lock succeeded
    }
});
```

### fcntlSync(fd, flags)

Synchronous fcntl(2). Throws an exception on error.

### seek(fd, offset, whence, [callback])

Asynchronous lseek(2).

callback will be given two arguments (err, currFilePos).

whence can be 0 (SEEK_SET) to set the new position in bytes to offset,
1 (SEEK_CUR) to set the new position to the current position plus offset
bytes (can be negative), or 2 (SEEK_END) to set to the end of the file
plus offset bytes (usually negative or zero to seek to the end of the file).

### seekSync(fd, offset, whence)

Synchronous lseek(2). Throws an exception on error.  Returns current
file position.



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