fern

Simple, efficient logging for Rust.

With fern, you can:

• Configure logging at runtime; make changes based off of user arguments or configuration
• Format log records without allocating intermediate results
• Output to stdout, stderr, log files and custom destinations
• Apply a blanket level filter and per-crate/per-module overrides
• Intuitively apply filters and formats to groups of loggers via builder chaining
• Log using the standard log crate macros

• fern documentation
• fern on crates.io
• fern in use (example program)

Testing

Fern has two separate tests which both require initializing the global logger, so the tests must be run separately. To test, use:

cargo test -- --skip test2
cargo test test2

To run the example program, use:

cargo run --example cmd-program
cargo run --example cmd-program -- --verbose