Using The Shell Effectively

How to win friends, and influence people (not really).

Once you get comfortable poking around with your shell, you start to wonder if there aren’t easier ways to do some common tasks. We’re constantly cd‘ing places, and running commands, and having to remember really long incantations just to list our files in reverse chronological order (ls -lrth).

I’ve compiled the following list of useful shortcuts for using the command line. They have all been tested on bash(1) and ksh(1). bash (Bourne Again SHell) is the default shell on MacOS and many Linux distributions. ksh (public domain Korn shell) is the default on OpenBSD, which happens to be what I use. There are many shells available, and we’ll look at more of them later, for now, I’ll stick to these two. To see what shell you are running, you can type:

$ env |grep SHELL


The idea that started this blog. How to I get to the beginning of the line? Here’s the answer to that as well as a few more movement tips:

ctrl + a
Move the cursor to the beginning of the line
ctrl + e
Move the cursor to the end of the line
esc + f
Move the cursor forward one word
esc + b
Move the cursor back one word

Just Kidding

Sometimes you don’t want to run what you just typed, how do you erase it?

ctrl + u
Erase everything you’ve typed on the line, and move the cursor to the beginning
ctrl + k
Delete from the cursor to the end of the line
esc, backspace
Erase the last word you typed

Tab Completion

Can’t remember what the command you’re looking for is, but you know it starts with the letters ba? Type ba followed by the <tab> key.

$ ba<tab>
backgammon   badsect      banner       basename     batch        battlestar

Oh, right, banner:

$ banner hello
 #    #  ######  #       #        ####
 #    #  #       #       #       #    #
 ######  #####   #       #       #    #
 #    #  #       #       #       #    #
 #    #  #       #       #       #    #
 #    #  ######  ######  ######   ####

This is also super useful if you’re just lazy. Don’t want to type ls? Just type l followed by <tab>! (OK, that doesn’t help at all.)

This can also be used on file names:

$ cd cotcli
$ ls
a-hard-link-to-a-new-file               a-symbolic-link-to-a-new-file
a-new-dir                               file.txt
$ cp f<tab>
$ cp file.txt new.txt

Tab will show you the list of things that matches, until there is only one thing left that can match, and then it will leave that there for you.

Find a command you previously ran

Did you just type out some really long complicated command, and now you have to do it again, but don’t want to type the whole thing? ctrl + p (or up arrow) to the rescue. Hitting ctrl + p once will bring up the most recent command you ran, and continuing to press that combination will cycle through your command history until you get to the end (beginning). ctrl + n (or down arrow) will do the opposite, assuming you’ve already gone back in time. That is, pressing this before you’ve pressed ctrl + p won’t do anything. You can also search through your command history with ctrl + r then type a few letters from a previous command and watch the magic.

ctrl + p
Previous history entry
ctrl + n
Next history entry
ctrl + r
Search for something you previously ran, after pressing this, just start typing and see what happens. Once you have a match, you can continue hitting ctrl + r to iterate through commands that match what you’ve already searched for.

Do That Again

Run the previous command again (does not work in ksh)

New Terms

(Basically this whole post was new terms, but here are a few extras)

A program that allows you to execute commands. Up until now we’ve been using the terms ‘shell’, ‘terminal’, and ‘command line’ somewhat interchangeably. In reality they are 3 different things.
The (B)ourne (A)gain (SH)ell. A very popular shell that is the default on MacOS and many Linux distributions.
The (K)orn (SH)ell. A less common shell that used to be the default on MacOS and is currently the default on OpenBSD.
A program to set and print environment. man env for more info.
A program to search for text. man grep for more info.
A program to print text as a “banner” (I used to have a printout of my name made on an old dot matrix printer using this program. My uncle made it for me when I visited his work back in the 80s. It was very cool.)
A program to copy one file to another. man cp for more info.