whatisare Unix-y commands that display a short description of other commands available on your system.
aproposis handy when you're looking for a particular function, say reading the contents of compressed files. It tends to be over-zealous with keywords, so for example, typing
apropos compare compressed filesreturns 184 one line descriptions on my system. Typing just
apropos compressedreturns a more manageable 22 descriptions:
$ apropos compressed bzcmp  (1) - compare bzip2 compressed files bzdiff  (1) - compare bzip2 compressed files ... zmore  (1) - file perusal filter for crt viewing of compressed text
whatiscomes in when you know the name of an unfamiliar command, but you want a simple description of it's purpose:
$ whatis zmore zmore  (1) - file perusal filter for crt viewing of compressed text
whatis) in Cygwin, you must first create the
whatisdatabase by running the
/usr/sbin/makewhatiscommand, probably with admin permissions to write the database.
Note (15 Jan 2014): apropos and whatis will not work from a Windows command prompt unless you've put the Cygwin bin directory ahead of the Windows and Windows\System32 directories in the PATH. Otherwise, apropos and whatis, which are shell scripts, will try to use the Windows 'find'command instead of the Cygwin 'find' command