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:

1for(var i = 0; i < 10; ++i) console.log(i)

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

1$ cat t.js
2for(var i = 0; i < 10; ++i) console.log(i)
3$ node --version
4v6.11.1
5$ node t.js  | head -n 1
60
7events.js:160
8      throw er; // Unhandled 'error' event
9      ^
10
11Error: write EPIPE
12    at exports._errnoException (util.js:1018:11)
13    at WriteWrap.afterWrite (net.js:800:14)

The process will cleanly exit if you require the module:

1$ cat t.js
2require("exit-on-epipe");
3for(var i = 0; i < 10; ++i) console.log(i)
4$ node t.js  | head -n 1
50

Installation

With npm:

1$ npm install exit-on-epipe

Usage

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

1require('exit-on-epipe');
2// ... rest of source

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

1var eoepipe = require('exit-on-epipe');
2eoepipe(stream);            // will exit process on an EPIPE error on stream
3eoepipe(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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