| # Debugging |
| |
| ## Logging |
| |
| Cargo uses the [`tracing`] crate to display debug log messages. |
| The `CARGO_LOG` environment variable can be set to enable debug logging, with a value such as `trace`, `debug`, or `warn`. |
| It also supports filtering for specific modules with comma-separated [directives]. |
| Feel free to use [shorthand macros] to help with diagnosing problems. |
| We're looking forward to making Cargo logging mechanism more structural! |
| |
| ```sh |
| # Outputs all logs with levels debug and higher |
| CARGO_LOG=debug cargo generate-lockfile |
| |
| # Don't forget that you can filter by module as well |
| CARGO_LOG=cargo::resolver=trace cargo generate-lockfile |
| |
| # This will print lots of info about the download process. `trace` prints even more. |
| CARGO_HTTP_DEBUG=true CARGO_LOG=network=debug cargo fetch |
| |
| # This is an important command for diagnosing fingerprint issues. |
| CARGO_LOG=cargo::compiler::fingerprint=trace cargo build |
| ``` |
| |
| [`tracing`]: https://docs.rs/tracing |
| [directive]: https://docs.rs/tracing-subscriber/latest/tracing_subscriber/filter/struct.EnvFilter.html#directives |
| [shorthand macros]: https://docs.rs/tracing/latest/tracing/index.html#shorthand-macros |
