When should I use `cargo new` vs. `cargo new --lib ` in Rust?

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1

I’m new to Rust and trying to understand the practical differences between:

  • cargo new my_project
  • cargo new --lib my_project
2

The only significant difference is whether it creates a src/lib.rs file (that will be compiled into a library crate which you can depend on from another package) or a src/main.rs file (that will be compiled into a binary crate which you can run). You can always change it later if you want to restructure your project.

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3

Never. Use cargo init or cargo init --lib instead :wink:
It does all the same things except it also works without a path argument to initialize a new package in the current working directory.

4

I think it's worth clarifying: cargo new foo creates a new directory named foo with a package of the same name, while cargo init makes a new package in the current directory, naming the package after the directory.

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5

... and cargo init foo does the same as cargo new foo, which is why I was (jokingly) saying to never use the latter. The init command can do everything that the new command does.

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6

BTW, the change is trivial. It's really just a matter whether src/lib.rs or src/main.rs exists. There's no other configuration to change. There's no special boilerplate needed.

Cargo.toml supports more customization of library paths and binaries in the project, but in the default you get from cargo new, it's all automatic.

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