How can I enable debug output?

Question

I tried printing something to the debug log, but I see no output:

julia> @debug "foo"

How can I enable debug output?

Answer 1

Use the JULIA_DEBUG environment variable to set debug output.

Set the value to the name of the module for which you want to enable debug logging:

julia> ENV["JULIA_DEBUG"] = Base

For the case of @debug calls in the REPL, set the module to Main:

julia> ENV["JULIA_DEBUG"] = Main
Main

julia> @debug "foo"
? Debug: foo
? @ Main REPL[6]:1

The special all value will enable debug logging for all modules:

julia> ENV["JULIA_DEBUG"] = "all"

If want to enable debugging during startup, you can set it through the shell:

$ JULIA_DEBUG=all julia

Answer 2

The other answer didn't work for me, so I did this which changes the global message filter level:

using Logging
disable_logging(Logging.Debug) # disable debug, info only
disable_logging(Logging.Debug-2000) # enable debug

see https://docs.julialang.org/en/v1/stdlib/Logging/#Logging.disable_logging