src/doc/rust-by-example/src/crates.md

   1 # Crates
   2
   3 A crate is a compilation unit in Rust. Whenever `rustc some_file.rs` is called,
   4 `some_file.rs` is treated as the *crate file*. If `some_file.rs` has `mod`
   5 declarations in it, then the contents of the module files would be inserted in
   6 places where `mod` declarations in the crate file are found, *before* running
   7 the compiler over it. In other words, modules do *not* get compiled
   8 individually, only crates get compiled.
   9
  10 A crate can be compiled into a binary or into a library. By default, `rustc`
  11 will produce a binary from a crate. This behavior can be overridden by passing
  12 the `--crate-type` flag to `lib`.