#logging #log #logger #glib


A logger which integrates with Glib message logging

1 unstable release

0.1.0 Feb 10, 2020

#45 in #glib

MIT license

185 lines

A simple logger that integrates with glib message logging mechanism. The logger is useful when one wants to integrate a piece of Rust code into a larger application which is already using glib/gio stack.


use std::env;

use log;

fn main() {
    env::set_var("G_MESSAGES_DEBUG", "all");


    log::info!("info message: {}", 2);
    log::warn!("warning message: {}", "foobar");
    log::debug!("Hello, world!");

Equivalent Vala code:

public void main() {
    Environment.set_variable ("G_MESSAGES_DEBUG", "all", false);

    info("info message: %d", 2);
    warning("warning message: %s", "foobar");
    debug("Hello, world!");


$ ./glib_logger_test
** INFO: 20:18:34.074: src/main.rs:12: info message: 2

** (process:39403): WARNING **: 20:18:34.076: src/main.rs:13: warning message: foobar
** (process:39403): DEBUG: 20:18:34.076: src/main.rs:15: Hello, world!


Due to slight differences between the meaning of respective log levels, the crate takes certain liberties. Specifically the log level mappings are:

  • Level::Trace, Level::Debug => G_LOG_LEVEL_DEBUG
  • Level::Error => G_LOG_LEVEL_CRITICAL
  • Level::Info => G_LOG_LEVEL_INFO
  • Level::Warn => G_LOG_LEVEL_WARNING

The G_LOG_LEVEL_ERROR (as produced via g_error() macro in C) is not mapped to any of log::Level enum values. The reason is that g_error() is fatal, while log::error!() is not.

The formatting is done fully in Rust. However, log filtering based on level is done in Glib. It is advisable to set G_MESSAGES_DEBUG=all environment variable.

Using Glib a domain can be set per file by using #define G_LOG_DOMAIN "my-domain" directly in C code. This functionality is not avaialble when using glib_logger, all logs are emitted with a NULL domain.