July 31, 2019
Everyone has their favorite editor, and some would fight to the death to defend their editor. Editors are also a common topic of blog posts — how to use a specific editor, how to configure it, what plugins to use, etc. People mention Vim, Emacs, Atom, Sublime Text, VS Code…but nobody ever talks about the editor that you use the most on the command line — the shell prompt. In my opinion, the shell prompt is actually quite a powerful editor, and I hope this post will serve to convince you.
Shells like Bash and Sh use a library called ‘Readline’ to handle their input. Zsh has its own implementation called ‘ZLE’, which works similarly to Readline. Therefore, learning to use Readline properly and efficiently can, and probably will, speed up your workflow.
This is not a beginner-level guide, so you should be familiar with the basics of adding text on the command line, such as tab completion. This post will introduce more advanced editing techniques to hopefully make you faster and more efficient. I will mostly be referring to Bash, and I will highlight the differences in ZSH, because those are the shells that I work with. However, they should work in all shells that use the Readline library. Also, for those of you who know about Readline editing modes, I will be using Emacs mode, because most of the time it’s the default. There’s also Vi mode, which lets you edit the current line using Vi-style bindings, but I personally don’t use this, as I don’t see the value in modal editing for a single line.
The notation I will use is Ctrl for the control key, and Meta for the meta key.
The meta key is commonly the alt key, but I recommend googling how the meta key works for your particular OS and terminal.
All commands that I’m covering here can also be found on the Readline Cheat Sheet, it might be useful to keep that bookmarked for future reference.
Here’s how you move around with more efficiency:
Ctrl-a: move to the beginning of the lineCtrl-e: move to the end of the lineMeta-f: move one word forwardMeta-b: move one word backwardCtrl-f: move one character forwardCtrl-b: move one character backwardCtrl-]: search forwards for a character and jump to it (like f in Vim)Ctrl-Meta-]: search backwards for a character and jump to it (like F in Vim)Searching is not set up by default in ZSH. Please see the ZSH Specifics section for information on how to set it up.
To clear the screen, use Ctrl-l.
One way to avoid re-typing commands is by using your history.
To search your history, press Ctrl-r and type a string.
Then, use Ctrl-p to go to older commands containing the search string, and Ctrl-n to go to newer ones.
You can use Ctrl-s to search forward in your history (but I don’t use this as much since I usually search for commands that I typed previously).
You can also type a command like “ls”, and then press Meta-p and Meta-n repeatedly to cycle through previous and next commands from your history that contain “ls”.
Another useful feature is reusing arguments of previous commands.
You’re probably familiar with expansions: !! for the previous command, !$ for the last argument of the previous command, and !:n-m for arguments from the one at position n up to and including the one at position m.
Readline also offers key bindings for arguments, and these are often more convenient to use than expansions.
To insert the last argument of the previous command, type Meta-..
Then you can press Meta-. repeatedly to cycle through all previous arguments.
You can also press the two key combinations Meta-NUM Ctrl-Meta-y to insert the previous argument at position NUM (with NUM being a number). The argument at position 0 is the command name.
This particular key binding doesn’t work in ZSH by default, please see the ZSH Specifics section for information on how to set it up.
In shells that use Readline, you can actually use Meta-. instead of Ctrl-Meta-y, as it takes a numeric argument and will work the same way, and it’s more convenient.
That is, you can type Meta-NUM Meta-. in the same way that you would with Ctrl-Meta-y.
Unfortunately, this does not apply to ZSH, as in ZLE, Meta-. counts arguments from the end.
Finally, there’s the undo command.
You can press Ctrl-_ repeatedly to undo all the changes you made to a line.
Readline also offers a bunch of useful key bindings for more efficient editing.
To delete:
Ctrl-k: kill (delete) from the cursor to the end of the lineCtrl-u: kill (delete) from the cursor to the beginning of the lineMeta-d: delete from the cursor to the end of the wordCtrl-w: delete from the cursor to the start of the previous space-delimited wordMeta-Delete: delete from from the cursor to the start of the previous word (Delete is the backspace key)
Ctrl-w and Meta-Delete is easier to explain with an example. Let’s say you have the string /some/path/here, with your cursor after the word here. If you type Ctrl-w, you’ll delete the whole path. Meta-Delete would delete individual components of the path, so typing Meta-Delete would delete the word ‘here’.Ctrl-d: delete the character under the cursorIf you ‘kill’ (delete) some text, you can paste (‘yank’) it into some other line with Ctrl-y.
You can cycle through everything you previously deleted with Meta-y.
You can also switch (‘transpose’) the last two words in your command with Meta-t, which is useful if you, for example, type the paths in a mv command in the wrong order.
If you have a lot of whitespace around your cursor, you can use Meta-\ to delete it.
This doesn’t work in ZSH by default, and I haven’t found a way to set it up yet.
Another one I use quite often is Meta-#, which comments the current line and starts a new one.
You can remember it easily due to the fact that Bash comments start with ‘#’.
There’s a command for this in ZSH, but you need to set a key binding, so see the ZSH Specifics section.
Finally, if you’re editing a really long command, you might want a full-featured editor.
You can open the current line in your $EDITOR with Ctrl-x Ctrl-e, which often pops up Vim, Nano, or Emacs.
When you save the file and quit the editor, it’ll run the command that you edited.
This is also a good way to avoid pastejacking, where you execute a potentially malicious command without knowing about it due to copy-pasting.
You can press Ctrl-x Ctrl-e and then paste it into the editor, double check the command, and then save and exit to execute it.
Yes, Bash has built-in macro functionality, where you can record a series of key strokes and then play them back whenever you want.
Type Ctrl-x ( to start recording a macro, and Ctrl-x ) to stop recording a macro.
Then, type Ctrl-x e to execute the macro that you just recorded.
This works in Bash and other shells that use Readline, but I haven’t found a way to make it work in ZSH yet.
ZSH gives you the key binding Ctrl-x Ctrl-k to kill the entire line.
You have to bind a key to the vi-find-next-char and vi-find-prev-char functions.
Put this in your .zshrc:
bindkey '^]' vi-find-next-char
bindkey '^\e]' vi-find-prev-char
Now you can use the same Bash bindings to jump to a character, forwards and backwards.
For this to work, you have to define your own ZSH ‘widget’, and then bind a key to it.
Put this in your .zshrc:
# Define the function
insert-arg-of-prev-cmd() {
# Get the argument
: ${NUMERIC:-1}
(( NUMERIC++ ))
# Get the previous command
words=($(fc -ln -1))
# Extract the argument
RBUFFER+="$words[$NUMERIC] "
# Move the cursor to the end of the line
zle end-of-line
}
## Create a ZLE widget
zle -N insert-arg-of-prev-cmd
## Bind 'Ctrl-Meta-y' to it
bindkey "\e^y" insert-arg-of-prev-cmd
Now you can use the same bindings as in Bash to insert a specific argument of a previous command.
There’s already a function for this in ZSH, but you need to bind a key to it.
Put this in your .zshrc:
bindkey '\e#' pound-insert
Now you can use the Bash-style key binding.