make logging to stderr available with vlib/log

[gergelyk]

Describe the feature

By convention application logs typically should go to stderr. Make it possible with vlib/log.

Use Case

I would like users to easily distinguish between computation results from my app (which go to stdout) and the logs.

Proposed Solution

I would recommend to:

• implement set_output_stream method that allows to select between stdout and stderr.
• make stderr default (if such backward incompatibility is acceptable).

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

Version used

V 0.3.2 865c0e

Environment details (OS name and version, etc.)

OS: macos, macOS, 12.6.1, 21G217
Processor: 10 cpus, 64bit, little endian, Apple M1 Pro
CC version: Apple clang version 14.0.0 (clang-1400.0.29.202)

[JalonSolov]

"typically"... where? :-) I've seen error logs go to stderr, but regular log messages often go to stdout.

It would, however, be nice to have the choice.

[gergelyk]

For instance

curl -v example.org

writes html to stdout and logs to stderr.

Topic also discussed here: https://stackoverflow.com/a/4919110

[gergelyk]

But I agree, example above is not enough to say "typically". Anyways, having a choice would be nice.

[gergelyk]

Logging module in Python also seems to select stderr by default:

https://github.com/python/cpython/blob/3.11/Lib/logging/__init__.py#L1084

If only errors should go to stderr, selection of the stream would need to be dependent of the logging level. Personally, I think that this would overcomplicate though.

[justinwyer]

The current log implementation handles writing to stdout via println, would there be support for dropping that special use case in favour of using stdout/stderr as just another file within log?