Getting Started

Installing Buck2

The latest set of buck2 executables can be found under the latest release page.

Additionally, for each bi-monthly release there is a dotslash file that is appropriate for checkin to a repository. This will automatically fetch the correct version and architecture for each user, and ensures a consistent build environment for each commit in the repo.

To get started, first install rustup, then compile the buck2 executable:

rustup install nightly-2024-02-01
cargo +nightly-2024-02-01 install --git https://github.com/facebook/buck2.git buck2

The above commands install buck2 into a suitable directory, such as $HOME/.cargo/bin, which you should then add to your $PATH:

Linux / macOS

export PATH=$HOME/.cargo/bin:$PATH

Windows Powershell

$Env:PATH += ";$HOME\.cargo\bin"

With Buck2 installed, you can build projects with buck2!

Windows configuration

Some of our rules use symlinks, which are disabled by default for non-admin Windows users. You can fix that by enabling Developer Mode.

Compiling your first project

This section covers the building of a 'hello_world' example project that contains a simple C++ binary. If you are interested in seeing how other languages can be built, take a look at the prelude example project, which contains Rust, C++, Python, and OCaml targets.

First, clone the buck2 repository and cd into the 'hello_world' project:

git clone https://github.com/facebook/buck2.git
cd buck2/examples/hello_world

buck2 init --git is all the setup you need to start building. This will use git submodule to pull buck2-prelude into your project:

buck2 init --git

To use another version control system, run buck2 init and manually download buck2-prelude into prelude at root.

buck2 init

To build the entire project, run:

Note: Requires clang and lld to be in the path

buck2 build //...

Note that this uses a simple C++ toolchain that requires a recent version of clang to be installed on your system. This can be installed with any package manager (ex. apt install clang, xcode-select --install on macOS, choco install llvm). After installing any external tools or changing your PATH, run buck2 kill before running a build.

To list all targets available in the project, run:

buck2 targets //...

To run the main C++ binary, run:

buck2 run //:main

The newly built binary can be found with the --show-output flag:

buck2 build //:main --show-output

Output:

Build ID: 0e890477-5b7f-4829-9ffe-662e572320a0
Jobs completed: 3. Time elapsed: 0.0s.
BUILD SUCCEEDED
root//:main buck-out/v2/gen/root/9f4d83578bb24895/__main__/main

Creating your first hello_world project

This section demonstrates how to create a simple C++ 'hello_world' project.

To get started, make a new folder for your project and cd into it.

mkdir hello_world
cd hello_world

Next, run buck2 init --git to initialize the project. This command will set up your project with git and pull in buck2-prelude as a submodule. Additionally, it will generate multiple files with default values.

buck2 init --git

Next, add the source code main.cpp ,

#include <iostream>
int main() {
    std::cout << "Hello from a C++ Buck2 program!" << std::endl;
}

Then, define a cxx_binary in the root BUCK file:

# BUCK
cxx_binary(
    name = "main",
    srcs = ["main.cpp"],
    link_style = "static",
)

If you try to build //:main at this point, you'll see an error about buck2 not being able to find toolchains//:cxx.

The final step is to define the necessary toolchain targets. For that project, you need system_cxx_toolchain and system_python_bootstrap_toolchain, which will pick up the necessary tools (clang++, python, and so on) from the system.

# toolchains/BUCK
load("@prelude//toolchains:cxx.bzl", "system_cxx_toolchain")
load("@prelude//toolchains:python.bzl", "system_python_bootstrap_toolchain")

system_cxx_toolchain(
    name = "cxx",
    visibility = ["PUBLIC"],
)

system_python_bootstrap_toolchain(
    name = "python_bootstrap",
    visibility = ["PUBLIC"],
)

At this point, your project should have the following files:

$ tree -a -I "buck-out|prelude|.git"
|-- .buckconfig
|-- .gitmodules
|-- BUCK
|-- main.cpp
`-- toolchains
    `-- BUCK

Now, you're ready to see the build in action.

To build the main C++ target, run:

buck2 build //:main

To run the main C++ target, run:

buck2 run //:main

In summary, a buck2 project requires:

1. A .buckconfig file in the root which has a [cells] section listing out cells
2. A prelude directory, which contains a collection of rules of your choice. buck2 init will pull in the buck2-prelude as a git submodule by default
3. If using the buck2-prelude, a toolchains directory that declares relevant toolchains. We provide some basic toolchains in prelude/toolchains
4. BUCK files that specify targets for your project

buck2 init --git will generate all of these with reasonable default values.

Learning More

You should now be ready to explore Buck2 for use in your own projects. You can explore the examples folder. Look out for more tutorials in the future.