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# [Erlang/OTP](https://www.erlang.org)
**Erlang** is a programming language and runtime system for building massively scalable soft real-time systems with requirements on high availability.
**OTP** is a set of Erlang libraries, which consists of the Erlang runtime system, a number of ready-to-use components mainly written in Erlang, and a set of design principles for Erlang programs. [Learn more about Erlang and OTP](http://erlang.org/doc/system_architecture_intro/sys_arch_intro.html).
[Release notes](http://erlang.org/download/otp_versions_tree.html) for all OTP versions.
[Learn how to program in Erlang](http://learnyousomeerlang.com/content).
## Examples
There are several examples [on the website](http://erlang.org/faq/getting_started.html) to help you get started. The below example defines a function `world/0` that prints "Hello, world" in the Erlang shell:
```erlang
-module(hello).
-export([world/0]).
world() -> io:format("Hello, world\n").
```
Save the file as `hello.erl` and run `erl` to enter the Erlang shell to compile the module.
```
Erlang/OTP 19 [erts-8.2] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]
Eshell V8.2 (abort with ^G)
1> c(hello).
{ok,hello}
2> hello:world().
Hello, world
ok
```
Learn more about the Erlang syntax of [modules](http://erlang.org/doc/reference_manual/modules.html), [functions](http://erlang.org/doc/reference_manual/functions.html) and [expressions](http://erlang.org/doc/reference_manual/expressions.html) on [Erlang.org](https://www.erlang.org).
## Installation
### Binary Distributions
Erlang/OTP is available as pre-built binary packages by most OS package managers.
```
apt-get install erlang
```
### Compiling from source
To compile Erlang from source, run the following commands. The complete building and installation instructions [can be found here](HOWTO/INSTALL.md).
```
git clone https://github.com/erlang/otp.git
cd otp
./otp_build autoconf
./configure
make
make install
```
Alternatively, you can use [Kerl](https://github.com/kerl/kerl), a script that lets you easily build Erlang with a few commands.
## Bug Reports
Please visit [bugs.erlang.org](https://bugs.erlang.org/issues/?jql=project%20%3D%20ERL) for reporting bugs. The instructions for submitting bugs reports [can be found here](https://github.com/erlang/otp/wiki/Bug-reports).
### Security Disclosure
We take security bugs in Erlang/OTP seriously. Please disclose the issues regarding security by sending an email to **erlang-security [at] erlang [dot] org** and not by creating a public issue.
## Contributing
We are grateful to the community for contributing bug fixes and improvements. Read below to learn how you can take part in improving Erlang/OTP. We appreciate your help!
### Contribution Guide
Read our [contribution guide](CONTRIBUTING.md) to learn about our development process, how to propose fixes and improvements, and how to test your changes to Erlang/OTP before submitting a pull request.
### Help Wanted
We have a list of [Help Wanted](https://bugs.erlang.org/issues/?jql=status%20%3D%20%22Help%20Wanted%22) bugs that we would appreciate external help from the community. This is a great place to get involved.
## License
Erlang/OTP is released under the [Apache License 2.0](http://www.apache.org/licenses/LICENSE-2.0).
> %CopyrightBegin%
>
> Copyright Ericsson AB 2010-2017. All Rights Reserved.
>
> Licensed under the Apache License, Version 2.0 (the "License");
> you may not use this file except in compliance with the License.
> You may obtain a copy of the License at
>
> http://www.apache.org/licenses/LICENSE-2.0
>
> Unless required by applicable law or agreed to in writing, software
> distributed under the License is distributed on an "AS IS" BASIS,
> WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
> See the License for the specific language governing permissions and
> limitations under the License.
>
> %CopyrightEnd%
## Awesome-Erlang
You can find more projects, tools and articles related to Erlang/OTP on the [awesome-erlang list](https://github.com/drobakowski/awesome-erlang). Add your project there.
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