Cygwin offers to display 4543 possibilities; what does it mean?

Question

A new kitten in the household has the habit of visiting me while I work, and it is able to make my system do things with a few pawpresses that I didn't know were possible. Windows change their stacking order, browsers magnify parts of previously-closed pages ... Just now, though, while I was working in vim in a window in front of my cygwin console window, the kitten walked across the left end of the keyboard. The cygwin window moved to the front, the cygwin cursor moved down one line from the prompt, and something printed:

Display all 4543 possibilities? (y or n)

I pressed 'n', but I wonder if anyone can tell me what keys my kitten pressed and what it woke up. I've used UNIX for years, but this message doesn't ring any bells.

TAB * 2 for command completion :-) You people are great. I wish I could give all of you the answer! Thanks. I'll go tell the cat.

Answer 1

Your cat hit the TAB key twice. That causes autocompletion to look for all the executable files in every folder in your PATH. Guess how many?

Normally you would type a few letters and then hit TAB, which, by default, will beep if there's more than one option or complete your text with the file that matches (completion is also programmable so that, for example, if you type 'svn chTAB' it will autocomplete to 'svn checkout').

Answer 2

It was most likely the tab completion being activated. In most modern shells, pressing a set of keys (or none at all), followed by tab (twice in some cases) will try to match the text you entered to the name one of the executables within your PATH.

Answer 3

Tab (for 2 seconds)

and Bash is asking you to list all the possible stuff in your PATH