[6a3a178] | 1 | # node-errno
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| 2 |
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| 3 | > Better [libuv](https://github.com/libuv/libuv)/[Node.js](https://nodejs.org)/[io.js](https://iojs.org) error handling & reporting. Available in npm as *errno*.
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| 4 |
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| 5 | [![npm](https://img.shields.io/npm/v/errno.svg)](https://www.npmjs.com/package/errno)
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| 6 | [![Build Status](https://secure.travis-ci.org/rvagg/node-errno.png)](http://travis-ci.org/rvagg/node-errno)
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| 7 | [![npm](https://img.shields.io/npm/dm/errno.svg)](https://www.npmjs.com/package/errno)
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| 8 |
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| 9 | * [errno exposed](#errnoexposed)
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| 10 | * [Custom errors](#customerrors)
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| 11 |
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| 12 | <a name="errnoexposed"></a>
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| 13 | ## errno exposed
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| 14 |
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| 15 | Ever find yourself needing more details about Node.js errors? Me too, so *node-errno* contains the errno mappings direct from libuv so you can use them in your code.
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| 16 |
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| 17 | **By errno:**
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| 18 |
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| 19 | ```js
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| 20 | require('errno').errno[3]
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| 21 | // → {
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| 22 | // "errno": 3,
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| 23 | // "code": "EACCES",
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| 24 | // "description": "permission denied"
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| 25 | // }
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| 26 | ```
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| 27 |
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| 28 | **By code:**
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| 29 |
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| 30 | ```js
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| 31 | require('errno').code.ENOTEMPTY
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| 32 | // → {
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| 33 | // "errno": 53,
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| 34 | // "code": "ENOTEMPTY",
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| 35 | // "description": "directory not empty"
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| 36 | // }
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| 37 | ```
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| 38 |
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| 39 | **Make your errors more descriptive:**
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| 40 |
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| 41 | ```js
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| 42 | var errno = require('errno')
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| 43 |
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| 44 | function errmsg(err) {
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| 45 | var str = 'Error: '
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| 46 | // if it's a libuv error then get the description from errno
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| 47 | if (errno.errno[err.errno])
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| 48 | str += errno.errno[err.errno].description
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| 49 | else
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| 50 | str += err.message
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| 51 |
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| 52 | // if it's a `fs` error then it'll have a 'path' property
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| 53 | if (err.path)
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| 54 | str += ' [' + err.path + ']'
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| 55 |
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| 56 | return str
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| 57 | }
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| 58 |
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| 59 | var fs = require('fs')
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| 60 |
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| 61 | fs.readFile('thisisnotarealfile.txt', function (err, data) {
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| 62 | if (err)
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| 63 | console.log(errmsg(err))
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| 64 | })
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| 65 | ```
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| 66 |
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| 67 | **Use as a command line tool:**
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| 68 |
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| 69 | ```
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| 70 | ~ $ errno 53
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| 71 | {
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| 72 | "errno": 53,
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| 73 | "code": "ENOTEMPTY",
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| 74 | "description": "directory not empty"
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| 75 | }
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| 76 | ~ $ errno EROFS
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| 77 | {
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| 78 | "errno": 56,
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| 79 | "code": "EROFS",
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| 80 | "description": "read-only file system"
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| 81 | }
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| 82 | ~ $ errno foo
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| 83 | No such errno/code: "foo"
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| 84 | ```
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| 85 |
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| 86 | Supply no arguments for the full list. Error codes are processed case-insensitive.
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| 87 |
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| 88 | You will need to install with `npm install errno -g` if you want the `errno` command to be available without supplying a full path to the node_modules installation.
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| 89 |
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| 90 | <a name="customerrors"></a>
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| 91 | ## Custom errors
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| 92 |
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| 93 | Use `errno.custom.createError()` to create custom `Error` objects to throw around in your Node.js library. Create error hierarchies so `instanceof` becomes a useful tool in tracking errors. Call-stack is correctly captured at the time you create an instance of the error object, plus a `cause` property will make available the original error object if you pass one in to the constructor.
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| 94 |
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| 95 | ```js
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| 96 | var create = require('errno').custom.createError
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| 97 | var MyError = create('MyError') // inherits from Error
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| 98 | var SpecificError = create('SpecificError', MyError) // inherits from MyError
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| 99 | var OtherError = create('OtherError', MyError)
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| 100 |
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| 101 | // use them!
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| 102 | if (condition) throw new SpecificError('Eeek! Something bad happened')
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| 103 |
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| 104 | if (err) return callback(new OtherError(err))
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| 105 | ```
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| 106 |
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| 107 | Also available is a `errno.custom.FilesystemError` with in-built access to errno properties:
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| 108 |
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| 109 | ```js
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| 110 | fs.readFile('foo', function (err, data) {
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| 111 | if (err) return callback(new errno.custom.FilesystemError(err))
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| 112 | // do something else
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| 113 | })
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| 114 | ```
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| 115 |
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| 116 | The resulting error object passed through the callback will have the following properties: `code`, `errno`, `path` and `message` will contain a descriptive human-readable message.
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| 117 |
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| 118 | ## Contributors
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| 119 |
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| 120 | * [bahamas10](https://github.com/bahamas10) (Dave Eddy) - Added CLI
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| 121 | * [ralphtheninja](https://github.com/ralphtheninja) (Lars-Magnus Skog)
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| 122 |
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| 123 | ## Copyright & Licence
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| 124 |
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| 125 | *Copyright (c) 2012-2015 [Rod Vagg](https://github.com/rvagg) ([@rvagg](https://twitter.com/rvagg))*
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| 126 |
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| 127 | Made available under the MIT licence:
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| 128 |
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| 129 | Permission is hereby granted, free of charge, to any person obtaining a copy
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| 130 | of this software and associated documentation files (the "Software"), to deal
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| 131 | in the Software without restriction, including without limitation the rights
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| 132 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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| 133 | copies of the Software, and to permit persons to whom the Software is furnished
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| 134 | to do so, subject to the following conditions:
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| 135 |
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| 136 | The above copyright notice and this permission notice shall be included in all
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| 137 | copies or substantial portions of the Software.
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| 138 |
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| 139 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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| 140 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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| 141 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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| 142 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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| 143 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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| 144 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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| 145 | SOFTWARE.
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