v/log at 5a4dbf19d0c449696f579591b3ea6a3f0b1c06ae - v

log provides your application logging services. You can log to file or to the console and use different logging levels, so that you are not overwhelmed by the logs.

Basic usage

The log module creates a default Log instance by default, and provides utility functions, that you can use to access it. Note: the default Log instance is thread safe.

That makes it very convenient to use in subsystems, without having to thread a log instance everywhere:

import log

fn abc() {
	log.info('some information')
	log.warn('a warning')
}

// this will not be visible, the default log level is .info:
log.debug('a debug message')

log.set_level(.debug)

// this will be now visible, the log level was changed to .debug:
log.debug('a debug message')

abc()

Advanced usage

You can also create your own log instances, with different options applied to them:

import log

fn main() {
	mut l := log.Log{}
	l.set_level(.info)
	l.set_full_logpath('./info.log')
	l.log_to_console_too()

	l.info('info')
	l.warn('warn')
	l.error('error')
	l.fatal('fatal') // panic, marked as [noreturn]
}

Backwards compatibility

After 2025/01/21, the log module outputs to stderr by default. Before that, it used stdout by default.

If you want to restore the previous behaviour, you have to explicitly call log.use_stdout() :

import os
import log

fn main() {
	// log.info('this will be printed to stderr after 2025/01/21 by default')
	log.use_stdout()
	log.info('this will be printed to stdout')
}

If you want to just silence the note about the stdout -> stderr, during the transition period, call l.set_output_stream(os.stderr()) explicitly.