Navigating the Command Line
I can't think of a better place to start than navigating the command line. As you start to do more and more in the shell, text in the command line can quickly become hard to handle. In this article I'll show some simple tricks for working with the command line more effectively.
Here's a quick reference diagram, the rest of the article goes into the details!
This article, examples and diagrams are available at github.com/dwmkerr/effective-shell.
- Basic Navigation
- Editing In-Place
- Clear the Screen
- Pro Tip: All The Keys!
- Pro Tip: Transposing!
- Closing Thoughts
Let's assume we have a very simple command we are writing, which is going to write a quote to a text file:
echo "The trouble with writing fiction is that it has to make sense, whereas real life doesn't. -- Iain M. Banks" >> quote.txt
Navigating around long lines of text is a slow process if you are only relying on the arrow keys, so take the time to learn the following shortcuts:
|Go to beginning / end|
|Go backwards / forwards one word|
|Delete a word / undo|
|Delete next word|
|Delete all the way to the beginning1|
|Delete all the way to the end|
Once you have the basic navigation commands down, the next essential is searching. Let's assume we've run the following three commands:
$ command1 param1 param2 param3 $ command2 param4 param5 param6 $ command3 param7 param8 param9
You can search backwards or forwards with
Ctrl + r and
Ctrl + s. This will search in the current command and then iteratively through previous commands:
This is useful for searching in the current command, but can be also used to quickly search backwards and forwards through the command history:
As you type, your command history is searched, the most recent commands coming first. Use the arrow keys to edit the command, press enter to execute it, or
Ctrl + g to cancel the search.
Here are the same commands applied to the original example:
|Search backwards / forwards|
|Run the command|
|Edit the command|
These tips and tricks are helpful, but if you are working with a really long or complex command, you might find it useful just to jump into your favourite editor.
Ctrl + x , Ctrl + e to edit-in place:
In a later article I'll talk a little more about how to configure the default editor.
Clear the Screen
Probably the shortcut I use the most is
Ctrl + l, which clears the screen without trashing your current command. Here's how it looks:
Pro Tip: All The Keys!
You can use the
bindkey command to see a list of all keyboard shortcuts:
$ bindkeys "^@" set-mark-command "^A" beginning-of-line "^B" backward-char "^D" delete-char-or-list "^E" end-of-line "^F" forward-char "^G" send-break "^H" backward-delete-char "^I" expand-or-complete "^J" accept-line "^K" kill-line "^L" clear-screen ...
This is an extremely useful command to use if you forget the specific keyboard shortcuts, or just want to see the shortcuts which are available.
Pro Tip: Transposing!
If you've mastered all of the commands here and feel like adding something else to your repertoire, try this:
Alt + t shortcut will transpose the last two words. Use
Ctrl + t to transpose the last two letters:
These were new to me when I was researching for this article. I can't see myself ever being able to remember the commands more quickly than just deleting the last two words or characters and re-typing them, but there you go!
If you are ever looking to go deeper, then search the web for GNU Readline, which is the library used under the hood to handle the command line in many shells. You can actually configure lower level details of how all shells which use readline work, with the
.inputrc configuration file.
The great thing about learning these shortcuts is that they will work in any prompt which uses GNU Readline. This means everything you've learnt applies to:
- The Python REPL
- The Node.js REPL
And probably a whole bunch more2.
All of these shortcuts should be familar to Emacs users. There is in fact a ‘Vi Mode’ option for readline, which allows you to use vi commands to work with text. You can enter this mode with
set -o vi, I'll likely come back to this in detail in a later article.
There's a great cheat sheet on emacs readline commands at readline.kablamo.org/emacs, which is a very useful reference if you want to dig deeper. For this article I've tried to focus on what I think are the most useful commands (and transpose just so you can show off!).
Hope that was useful! GIFs were made with LICEcap.