# exit-on-epipe

Cleanly exit on pipe errors in NodeJS scripts.

NOTE: The underlying problem was addressed in 8.x NodeJS versions but the fix
was not backported to 6.x and other versions of NodeJS.

These errors are common in pipelines that involve NodeJS scripts. For example,
take a simple script that prints out 10 lines:

```js
for(var i = 0; i < 10; ++i) console.log(i)
```

NodeJS will print an error message if the output is truncated:

```bash
$ cat t.js
for(var i = 0; i < 10; ++i) console.log(i)
$ node --version
v6.11.1
$ node t.js  | head -n 1
0
events.js:160
      throw er; // Unhandled 'error' event
      ^

Error: write EPIPE
    at exports._errnoException (util.js:1018:11)
    at WriteWrap.afterWrite (net.js:800:14)
```

The process will cleanly exit if you require the module:

```bash
$ cat t.js
require("exit-on-epipe");
for(var i = 0; i < 10; ++i) console.log(i)
$ node t.js  | head -n 1
0
```

## Installation

With [npm](https://www.npmjs.org/package/exit-on-epipe):

```bash
$ npm install exit-on-epipe
```

## Usage

For basic scripts, requiring at the top of the source file suffices:

```js
require('exit-on-epipe');
// ... rest of source
```

For more advanced situations (e.g. handing other streams), call the module:

```js
var eoepipe = require('exit-on-epipe');
eoepipe(stream);            // will exit process on an EPIPE error on stream
eoepipe(stream, handler);   // will call handler() instead of process.exit
```

## Interface

The module exports a single function (exposed as the variable `eoepipe`).

`eoepipe(stream, bail)` will attach an error handler to `stream` which will:

- call the `bail` function if the error `.code` is `"EPIPE"` or `.errno` is `32`
- defer to the default behavior if there are no other error handlers
- noop if the error is not `EPIPE` and if there are other error handlers

If the `bail` function is not specified, `process.exit` is used.

If the `stream` parameter is not specified, no action will be taken

## Notes

The script will not perform any action if `process` or `process.stdout` are not
available.  It is safe to use in a web page.

## License

Please consult the attached LICENSE file for details.  All rights not explicitly
granted by the Apache 2.0 license are reserved by the Original Author.

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