# Workspaces

When the code base is getting larger, you might need to work on **multiple crates on the same project**. Rust supports this via Workspaces. You can **build, run tests or generate docs for all crates** at once by running `cargo` commands from the project root.

⭐️ When working on multiple crates same time, there is a higher possibility to having shared dependencies on crates. To prevent downloading and compiling the same dependency multiple times, Rust uses a **shared build directory** under the project root, while running `cargo build` from the project root.

```rust
// # Think we run
mkdir greetings
touch greetings/Cargo.toml
cargo new greetings/lib
cargo new --bin greetings/examples/hello

// # That generates,
.
├── Cargo.toml
├── examples
│  └── hello
│     ├── Cargo.toml
│     └── src
│        └── main.rs
└── lib
   ├── Cargo.toml
   └── src
      └── lib.rs

// # Think we modify following files

// 01. greetings/Cargo.toml
[workspace]
members = [
    "lib",
    "examples/hello"
]

// 02.1 greetings/lib/Cargo.toml
[package]
name = "greetings"
version = "0.1.0"
authors = ["Dumindu Madunuwan"]

[dependencies]

// 02.2 greetings/lib/src/lib.rs
pub fn hello() {
    println!("Hello, world!");
}

// 03.1 greetings/examples/hello/Cargo.toml
[package]
name = "hello"
version = "0.1.0"
authors = ["Dumindu Madunuwan"]

[dependencies]
greetings = { path = "../../lib" }

// 03.2 greetings/examples/hello/src/main.rs
extern crate greetings;

fn main() {
    greetings::hello();
}
```

> 🔎 [rust-lang/rust source folder](https://github.com/rust-lang/rust/tree/master/src) is a good example for a workspace.