The Etc module provides access to information typically stored in files in the
/etc directory on Unix systems.

The information accessible consists of the information found in the /etc/passwd
and /etc/group files, plus information about he system's temporary directory
(/tmp) and configuration directory (/etc).

The Etc module provides a more reliable way to access information about the
logged in user than environment variables such as +$USER+.

WWW: https://github.com/ruby/etc