# rustfmt A tool for formatting Rust code according to style guidelines. ## Gotchas * For things you do not want rustfmt to mangle, use ```rust #[rustfmt_skip] ``` * When you run rustfmt use a file called rustfmt.toml to override the settings in default.toml * We create a functioning executable called rustfmt in the target directory ## How to build and test You'll need a pretty up to date version of the **nightly** version of Rust. `cargo build` to build. `cargo test` to run all tests. `cargo run -- filename` to run on a file, if the file includes out of line modules, then we reformat those too. So to run on a whole module or crate, you just need to run on the top file. You'll probably want to specify the write mode. Currently, there are the replace, overwrite and display mode. The replace mode is the default and overwrites the original files after renaming them. In overwrite mode, rustfmt does not backup the source files. To print the output to stdout, use the display mode. The write mode can be set by passing the `--write-mode` flag on the command line. `cargo run -- filename --write-mode=display` prints the output of rustfmt to the screen, for example.