# posix-character-classes [](https://www.npmjs.com/package/posix-character-classes) [](https://npmjs.org/package/posix-character-classes) [](https://npmjs.org/package/posix-character-classes) [](https://travis-ci.org/jonschlinkert/posix-character-classes)
> POSIX character classes for creating regular expressions.
## Install
Install with [npm](https://www.npmjs.com/):
```sh
$ npm install --save posix-character-classes
```
Install with [yarn](https://yarnpkg.com):
```sh
$ yarn add posix-character-classes
```
## Usage
```js
var posix = require('posix-character-classes');
console.log(posix.alpha);
//=> 'A-Za-z'
```
## POSIX Character classes
The POSIX standard supports the following classes or categories of charactersh (note that classes must be defined within brackets):
| **POSIX class** | **Equivalent to** | **Matches** |
| --- | --- | --- |
| `[:alnum:]` | `[A-Za-z0-9]` | digits, uppercase and lowercase letters |
| `[:alpha:]` | `[A-Za-z]` | upper- and lowercase letters |
| `[:ascii:]` | `[\x00-\x7F]` | ASCII characters |
| `[:blank:]` | `[ \t]` | space and TAB characters only |
| `[:cntrl:]` | `[\x00-\x1F\x7F]` | Control characters |
| `[:digit:]` | `[0-9]` | digits |
| `[:graph:]` | `[^[:cntrl:]]` | graphic characters (all characters which have graphic representation) |
| `[:lower:]` | `[a-z]` | lowercase letters |
| `[:print:]` | `[[:graph] ]` | graphic characters and space |
| `[:punct:]` | ``[-!"#$%&'()*+,./:;<=>?@[]^_`{ | }~]`` | all punctuation characters (all graphic characters except letters and digits) |
| `[:space:]` | `[ \t\n\r\f\v]` | all blank (whitespace) characters, including spaces, tabs, new lines, carriage returns, form feeds, and vertical tabs |
| `[:upper:]` | `[A-Z]` | uppercase letters |
| `[:word:]` | `[A-Za-z0-9_]` | word characters |
| `[:xdigit:]` | `[0-9A-Fa-f]` | hexadecimal digits |
## Examples
* `a[[:digit:]]b` matches `a0b`, `a1b`, ..., `a9b`.
* `a[:digit:]b` is invalid, character classes must be enclosed in brackets
* `[[:digit:]abc]` matches any digit, as well as `a`, `b`, and `c`.
* `[abc[:digit:]]` is the same as the previous, matching any digit, as well as `a`, `b`, and `c`
* `[^ABZ[:lower:]]` matches any character except lowercase letters, `A`, `B`, and `Z`.
## About
### Contributing
Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new).
### Building docs
_(This project's readme.md is generated by [verb](https://github.com/verbose/verb-generate-readme), please don't edit the readme directly. Any changes to the readme must be made in the [.verb.md](.verb.md) readme template.)_
To generate the readme, run the following command:
```sh
$ npm install -g verbose/verb#dev verb-generate-readme && verb
```
### Running tests
Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:
```sh
$ npm install && npm test
```
### Author
**Jon Schlinkert**
* [github/jonschlinkert](https://github.com/jonschlinkert)
* [twitter/jonschlinkert](https://twitter.com/jonschlinkert)
### License
Copyright © 2017, [Jon Schlinkert](https://github.com/jonschlinkert).
Released under the [MIT License](LICENSE).
***
_This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.5.0, on April 20, 2017._