Today's hint is for those who spend a fair bit of time in Terminal. If you do, you're probably aware that Terminal tracks your command history--that is, it keeps a record of the commands you've used, and you can scroll through those historical commands. Press the Up Arrow key from the command prompt, and you'll see the most-recently used command; each additional press moves further back through history, and the Down Arrow key moves forward in the history file.
There are a couple tricks to getting even more out of this history file, though. First, you can search through it by pressing Control-R to bring up the (reverse-i-search) prompt. Once the prompt appears, enter a portion of the command name you'd like to find, ssh for instance, and then just keep pressing Control-R to see each match in the history file. When the one you want to re-use appears, press Return to execute the command.
While this is nice, it's a bit of a pain to press Control-R. So another option, and the focus of this hint, is to give the Up Arrow and Down Arrow keys another role: they'll do what Control-R does, but only when you've already started typing a command.
So in normal use, if you haven't started typing a command, the Up Arrow key will show the last-used command. But if you start typing a command, then the Up Arrow key will actually run a search of the command history, and show the last-used command that begins with the letters you've already typed. (This is subtly different than Control-R, which finds the string you've typed anywhere within a previously-used command. I think this difference, though, actually makes this hint more useful.)
To make this work, you need to edit your user's .profile file, which is in the top level of your user's folder. Open Terminal, and type nano .profile. If you have an existing file, it will open for editing; otherwise, you'll see a blank screen.
Add these two lines to the file, but note you can't copy and paste these lines, as there are special characters in there (which I'll explain how to enter).
The special characters are represented by the ^[[A and ^[[B bits on each line. These are, respectively, the Up Arrow and Down Arrow keys. So how do you type them in nano?
Copy and paste the first part of each line above (bind '"), and then press Escape-V. When you do, you'll see a little tag at the bottom of the window that reads [ Verbatim Input ]. Now press the Up Arrow (or Down Arrow, depending on the line), and you'll see the above codes appear (and you'll exit Verbatim Input mode when you press the arrow key). After that, just copy and paste the rest of each line, and you're done.
Save the file by pressing Control-X (for exit), Y (for yes to save changes), and Return (to accept the filename). Now just open a new Terminal window, type out part of a command you use a lot, and experiment with the Up Arrow and Down Arrow keys for browsing through the command-specific history.
If you decide you dislike this feature, just edit the .profile file again and remove the two lines you added. Personally, though, I much prefer this method of browsing through command-specific history.
This story, "Better Command History Browsing in Terminal" was originally published by Macworld.