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# steno [](https://www.npmjs.org/package/steno) [](https://travis-ci.org/typicode/steno)
> Simple file writer with __atomic writing__ and __race condition prevention__.
Can be used as a drop-in replacement to `fs.writeFile()`.
Built on [graceful-fs](https://github.com/isaacs/node-graceful-fs) and used in [lowdb](https://github.com/typicode/lowdb).
## Install
```
npm install steno --save
```
## Usage
```javascript
const steno = require('steno')
steno.writeFile('file.json', data, err => {
if (err) throw err
})
```
## The problem it solves
### Without steno
Let's say you have a server and want to save data to disk:
```javascript
var data = { counter: 0 }
server.post('/', (req, res) => {
// Increment counter
++data.counter
// Save data asynchronously
fs.writeFile('data.json', JSON.stringify(data), err => {
if (err) throw err
res.end()
})
})
```
Now if you have many requests, for example `1000`, there's a risk that you end up with:
```javascript
// In your server
data.counter === 1000
// In data.json
data.counter === 865 // ... or any other value
```
Why? Because, `fs.write` doesn't guarantee that the call order will be kept. Also, if the server is killed while `data.json` is being written, the file can get corrupted.
### With steno
```javascript
server.post('/increment', (req, res) => {
++data.counter
steno.writeFile('data.json', JSON.stringify(data), err => {
if (err) throw err
res.end()
})
})
```
With steno you'll always have the same data in your server and file. And in case of a crash, file integrity will be preserved.
if needed, you can also use `steno.writeFileSync()` which offers atomic writing too.
__Important: works only in a single instance of Node.__
## License
MIT - [Typicode](https://github.com/typicode)
|