How to build CARLA on Linux

<h1>How to build CARLA on Linux</h1>

!!! note
    CARLA requires Ubuntu 16.04 or later.

Install the build tools and dependencies

```
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt-get install build-essential clang-5.0 lld-5.0 g++-7 ninja-build python python-pip python3 python3-pip libboost-python-dev python-dev tzdata sed curl wget unzip autoconf libtool
pip2 install --user setuptools nose2
pip3 install --user setuptools nose2
```

To avoid compatibility issues between Unreal Engine and the CARLA dependencies,
the best configuration is to compile everything with the same compiler version
and C++ runtime library. We use clang 5.0 and LLVM's libc++. We recommend to
change your default clang version to compile Unreal Engine and the CARLA
dependencies

```sh
sudo update-alternatives --install /usr/bin/clang++ clang++ /usr/lib/llvm-5.0/bin/clang++ 101
sudo update-alternatives --install /usr/bin/clang clang /usr/lib/llvm-5.0/bin/clang 101
```

Build Unreal Engine
-------------------

!!! note
    Unreal Engine repositories are set to private. In order to gain access you
    need to add your GitHub username when you sign up at
    [www.unrealengine.com](https://www.unrealengine.com).

Download and compile Unreal Engine 4.19. Here we will assume you install it at
`~/UnrealEngine_4.19", but you can install it anywhere, just replace the path
where necessary.

```sh
git clone --depth=1 -b 4.19 https://github.com/EpicGames/UnrealEngine.git ~/UnrealEngine_4.19
cd ~/UnrealEngine_4.19
./Setup.sh && ./GenerateProjectFiles.sh && make
```

Check Unreal's documentation
["Building On Linux"](https://wiki.unrealengine.com/Building_On_Linux) if any of
the steps above fail.

Build CARLA
-----------

Clone or download the project from our
[GitHub repository](https://github.com/carla-simulator/carla)

```sh
git clone https://github.com/carla-simulator/carla
```

Note that the `master` branch contains the latest fixes and features, for the
latest stable code may be best to switch to the latest release tag.

Now you need to download the assets package, to do so we provide a handy script
that downloads and extracts the latest version (note that the package is >10GB,
this step might take some time depending on your connection)

```sh
./Update.sh
```

For CARLA to find your Unreal Engine's installation folder you need to set the
following environment variable

```sh
export UE4_ROOT=~/UnrealEngine_4.19
```

You can also add this variable to your `~/.bashrc` or `~/.profile`.

Now that the environment is set up, you can run make to run different commands

```sh
make launch   # Compiles CARLA and launches Unreal Engine's Editor.
make package  # Compiles CARLA and creates a packaged version for distribution.
make help     # Print all available commands.
```

Updating CARLA
--------------

Every new release of CARLA we release a new package with the latest changes in
the CARLA assets. To download the latest version and recompile CARLA, run

```sh
make clean
git pull
./Update.sh
make launch
```