%{gem_dir}

/usr/share/gems

Top directory for the gem structure.

%{gem_instdir}

%{gem_dir}/gems/%{gem_name}-%{version}

Directory with the actual content of the gem.

%{gem_libdir}

%{gem_instdir}/lib

The library directory of the gem.

%{gem_cache}

%{gem_dir}/cache/%{gem_name}-%{version}.gem

The cached gem.

%{gem_spec}

%{gem_dir}/specifications/%{gem_name}-%{version}.gemspec

The gem specification file.

%{gem_docdir}

%{gem_dir}/doc/%{gem_name}-%{version}

The RDoc documentation of the gem.

%{gem_extdir_mri}

%{_libdir}/gems/ruby/%{gem_name}-%{version}

The directory for gem extension.