Search notes:
apt-config
apt-config [--empty] [--format '%f "%v";%n'] [-o=config_string] [-c=config_file] {shell | dump | {-v | --version} | {-h | --help}}
Dump the values of some given configuration directives:
$ apt-config dump | grep -E 'Dir |Dir::Etc |Dir::Etc::main |Dir::Etc::source' | column -t
Dir "/";
Dir::Etc "etc/apt";
Dir::Etc::sourcelist "sources.list";
Dir::Etc::sourceparts "sources.list.d";
Dir::Etc::main "apt.conf";
Dump the values of «second level directories»:
$ apt-config dump | grep -E 'Dir::[^:]+ ' | sort | column -t
Dir::Bin "";
Dir::Cache "var/cache/apt";
Dir::Etc "etc/apt";
Dir::Ignore-Files-Silently "";
Dir::Log "var/log/apt";
Dir::Media "";
Dir::State "var/lib/apt";