whohas is a command line tool that allows you to query several package collections at once. It currently supports Arch Linux, Debian, Fedora, Gentoo, Slackware (+ linuxpackages.net), Source Mage Linux, FreeBSD, NetBSD, OpenBSD, Fink and DarwinPorts repositories. whohas was designed to help package maintainers find ebuilds, pkgbuilds, and similar package definitions from other distributions to learn from. However, it can also be used by normal users who want to know which distribution provides certain packages, and which version of a given package is in use in each distribution or in each release of a distribution.