Aproplus helps you quickly find system and library functions but also to view their associated man pages.
To use Aproplus, just type a term in the search area and hit the enter key. Click on an item of interest in the list on the left, and the man page will be displayed on the right.
If there are variations of a specific entry, a dropdown will allow you to view the different variants. NOTE: Aproplus can only be purchased via the Mac App Store (the download link redirects you to its App Store page). To purchase/download applications via the App Store an Apple account is required.