Linux: Logs directory may be more appropriate under XDG_CONFIG_HOME

[srenfo]

user_log_dir is currently documented as follows:

        Unix:       ~/.cache/<AppName>/log  # or under $XDG_CACHE_HOME if defined

but I can't find a source for this convention (see also #26).

systemd uses $XDG_CONFIG_HOME/log/ for its LogsDirectory:

Directory	Below path for system units	Below path for user units	Environment variable set
RuntimeDirectory=	/run/	$XDG_RUNTIME_DIR	$RUNTIME_DIRECTORY
StateDirectory=	/var/lib/	$XDG_CONFIG_HOME	$STATE_DIRECTORY
CacheDirectory=	/var/cache/	$XDG_CACHE_HOME	$CACHE_DIRECTORY
LogsDirectory=	/var/log/	$XDG_CONFIG_HOME/log/	$LOGS_DIRECTORY
ConfigurationDirectory=	/etc/	$XDG_CONFIG_HOME	$CONFIGURATION_DIRECTORY

This is technically unrelated to the XDG spec but I suggest following this convention is better than following none. Of course, if someone can find a proper explicit convention that would be even better.

[KenKundert]

It appears that XDG is suggesting $XDG_STATE_HOME for log files:

The $XDG_STATE_HOME contains state data that should persist between (application) restarts, but that is not important or portable enough to the user that it should be stored in $XDG_DATA_HOME. It may contain:

actions history (logs, history, recently used files, …)

current state of the application that can be reused on a restart (view, layout, open files, undo history, …)

[sellout]

One historical note (that may have influenced the systemd decision) is that earlier versions of the XDG Base Directory spec didn’t have XDG_STATE_HOME, so it left the place for logs, etc. up in the air.

XDG_STATE_HOME is definitely the correct place now.