stdout / stderr logs

[uggyuggy]

Hi,

Starting the daemon, it looks all "information" logs goes into stderr (and nothing to stdout)

$ ./certstream-server-go_1.7.0-rc_linux_amd64 1> 111 2> 222

 $ tail 222

2024/08/19 15:08:37 server.go:287: Starting webserver on 127.0.0.1:8080
2024/08/19 15:08:37 ct-watcher.go:90: Checking for new ct logs...
...

Is it expected behavior to log this into stderr instead of stdout ?

[d-Rickyy-b]

Go uses stderr as output by default for their basic logging library (src/log/log.go).

This is in compliance with the POSIX standard, which defines the three streams (stdin, stdout, stderr) as follows:

standard input (for reading conventional input), standard output (for writing conventional output), and standard error (for writing diagnostic output).

(see also https://pubs.opengroup.org/onlinepubs/9699919799/functions/stderr.html)

This project uses the Go standard logger. It's certainly debatable if logs are "conventional output for a server application", since it's not comparable with say a CLI application. There has been a nice conversation on reddit about exactly this topic: https://www.reddit.com/r/golang/comments/15ndgdy/slog_splitting_stdoutstderr_streams/

Since Go 1.21, structured logging comes right out of the box (log/slog). I haven't had the time yet to properly check out slog, but I assume that we should be using it. While we're at that, we could also change the behavior so that regular logs go to stdout and warnings/errors go to stderr.

To answer your question:

Is it expected behavior to log this into stderr instead of stdout ?

It is expected, but not necessarily intended in the long term.

[uggyuggy]

Thank you for the detailed answer.