Package Layout

.
├── Cargo.lock
├── Cargo.toml
├── src/
│   ├── lib.rs                      # The default library file is src/lib.rs.
│   ├── main.rs                     # The default executable file is src/main.rs.
│   └── bin/                        # Other executables can be placed in src/bin/,
│       ├── named-executable.rs     # even in library projects.
│       ├── another-executable.rs
│       └── multi-file-executable/
│           ├── main.rs
│           └── some_module.rs
├── benches/
│   ├── large-input.rs
│   └── multi-file-bench/
│       ├── main.rs
│       └── bench_module.rs
├── examples/
│   ├── simple.rs                   # cargo run --example simple
│   └── multi-file-example/
│       ├── main.rs
│       └── ex_module.rs
└── tests/                          # Integration tests go in the tests directory.
    ├── some-integration-tests.rs   # Tests in your src files should be unit tests
    └── multi-file-test/            # and documentation tests.
        ├── main.rs
        └── test_module.rs

If you’re building a non-end product, such as a rust library that other rust packages will depend on, put Cargo.lock in your .gitignore.

• A package is a bundle of one or more crates - as defined by a Cargo.toml file
• A crate is the smallest amount of code that the Rust compiler considers at a time.
• A crate can come in one of two forms: a binary crate (must have a function called main⮳) or a library crate.
• A package can contain as many binary crates as you like, but at most only one library crate.
• If a package contains src/main.rs and src/lib.rs, it has two crates: a binary and a library, both with the same name as the package.