Equery

equery is a tool to make several common portage operations simpler. Among other operations, it can display package dependencies, metadata, and installed files.

Installation
Equery is available as part of the package in portage.

Capabilities
To see a list of all equery's capabilities, simply run it without arguments:

Each equery module can be run using either the full name or the indicated short name. For example, to get a list of what depends on a certain installed package, the depends module would be used.

Descriptions of other modules and additional command line flags can be found in the man page

Aliases
If you found yourself using equery all the time to check USE flags, package files... you could write down a few handy aliases with `eq' as a prefix and the letter used by a function. I use `~/.aliasrc' for bash which could be used for any shell and `~/.oh-my-zsh/lib/aliases.zsh' for zsh because I use oh-my-zsh.

External Resources

 * http://en.gentoo-wiki.com/wiki/Equery