bash - enable single tab hit once auto completion
If it's the former I have no clue, though ctrl-R kind of does that. If the latter, you can create a file called .inputrc in your home directory with the following lines:
# vi ~/.inputrc
### tab auto-completion
set show-all-if-ambiguous on
set show-all-if-unmodified on
### if you don't want case-sensitivity
set completion-ignore-case on
### bash history completion to complete what's already on the line
Note: .inputrc will get read whenever you start a new bash process.
Note: After you modify ~/.inputrc, restart your shell or use Ctrl+X, Ctrl+R to tell it to re-read ~/.inputrc.