but i also mentioned that i'm not sure on how to use this key to go to the next or previous match command. i found it now :)
once you hit ctrl-r to do a "reverse incremental search". as you type, bash will search your command history and auto-fill the most recent command that matches the pattern you type in. hit ctrl-r again to go to the next most recent match. just hit ctrl-r again & again until you found the command you looking for. and if you want to go the previous match command, you can hit ctrl-s, but make sure you do this first:
disable the default terminal setting for ctrl-s & ctrl-q which is to lock & unlock your terminal.
$ stty -ixon