How prevalent is XDG? The only place I have seen it used is on
[Caddy's Dockerfile].<p>The defaults do not seem to match what the [Filesystem Hierarchy
Standard] is proposing, but they do seem reasonable:<p><pre><code> # user data (/usr/share)
XDG_DATA_HOME="${XDG_DATA_HOME:-$HOME/.local/share}"
# config files (/etc)
XDG_CONFIG_HOME="${XDG_CONFIG_HOME:-$HOME/.config}"
# cache files (/usr/share)
XDG_CACHE_HOME="${XDG_CACHE_HOME:-$HOME/.cache}"
# state files (/var/lib)
XDG_STATE_HOME="${XDG_STATE_HOME:-$HOME/.local/state}"
[Caddy's Dockerfile]: https://github.com/caddyserver/caddy-docker/blob/master/Dockerfile.tmpl#L40
[Filesystem Hierarchy Standard]: https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard</code></pre>