zwischenzugs Uncategorized August 25, 2019July 13, 2020

4 Minutes

Intro

Most guides to bash history shortcuts exhaustively list all of the shortcuts available to you.

The problem I always had with that was that I would use them once, and then glaze over as I tried out all the possibilities. Then I’d move onto my working day and completely forget them, retaining only the well-known !! trick I learned when I first started using bash.

So most never got committed to memory.

Here I outline the shortcuts I actually use every day. When people see me use them they often ask me “what the hell did you do there!?”, conferring God-like status on me with minimal effort or intelligence required.

I recommend using one a day for a week, then moving onto the next one. It’s worth taking your time to get them under your fingers, as the time you save will be significant in the long run.

1) !$ – The ‘Last Argument’ One

If you only take one shortcut from this article, make it this one.

It substitutes in the last argument of the last command into your line.

Consider this scenario:

$ mv /path/to/wrongfile /some/other/place
mv: cannot stat '/path/to/wrongfile': No such file or directory

Ach, I put the wrongfile filename in my command. I should have put rightfile instead.

You might decide to fully re-type the last command, and replace wrongfile with rightfile.

Instead, you can type:

$ mv /path/to/rightfile !$
mv /path/to/rightfile /some/other/place

and the command will work.

There are other ways to achieve the above in bash with shortcuts, but this trick of re-using the last argument of the last command is one I use the most.

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2) !:2 – The ‘nth Argument’ One

Ever done anything like this?

$ tar -cvf afolder afolder.tar
tar: failed to open

Like others, I get the arguments to tar (and ln) wrong more than I would like to admit:

When you mix up arguments like that, you can run:

$ !:0 !:1 !:3 !:2
tar -cvf afolder.tar afolder

and your reputation will be saved.

The last command’s items are zero-indexed, and can be substituted in with the number after the !:.

Obviously, you can also use this to re-use specific arguments from the last command rather than all of them.

3) !:1-$ – The ‘All The Arguments’ One

Imagine you run a command, and realise that the arguments were correct, but

$ grep '(ping|pong)' afile

I wanted to match ping or pong in a file, but I used grep rather than egrep.

I start typing egrep, but I don’t want to re-type the other arguments, so I can use the !:1-$ shortcut to ask for all the arguments to the previous command from the second one (remember they’re zero-indexed) to the last one (represented by the $ sign):

$ egrep !:1-$
egrep '(ping|pong)' afile
ping

You don’t need to pick 1-$, you can pick a subset like 1-2, or 3-9 if you had that many arguments in the previous command.

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Learn Git the Hard Way
Learn Terraform the Hard Way

4) !-2:$ – The ‘Last But n‘ One

The above shortcuts are great when I know immediately how to correct my last command, but often I run commands after the orignal one which mean that the last command is no longer the one I want to reference.

For example, using the mv example from before, if I follow up my mistake with an ls check of the folder’s contents:

$ mv /path/to/wrongfile /some/other/place
mv: cannot stat '/path/to/wrongfile': No such file or directory
$ ls /path/to/
rightfile

…I can no longer use the !$ shortcut.

In these cases, you can insert a -n: (where n is the number of commands to go back in the history) after the ! to grab the last argument from an older command:

$ mv /path/to/rightfile !-2:$
mv /path/to/rightfile /some/other/place

Again, once learned, you may be surprised at how often you need it.

5) !$:h – The ‘Get Me The Folder’ One

This one looks less promising on the face of it, but is something I use dozens of times daily.

Imagine I run a command like this:

$ tar -cvf system.tar /etc/system
 tar: /etc/system: Cannot stat: No such file or directory
 tar: Error exit delayed from previous errors. 

The first thing I might want to do is go to the /etc folder to see what’s in there and work out what I’ve got wrong.

I can do this at a stroke with:

$ cd !$:h
cd /etc

What this one does is say: get the last argument to the last command (/etc/system), and take off its last filename component, leaving only the /etc.

6) !#:1 – The ‘The Current Line’ One

I spent years occasionally wondering if I could reference an argument on the current line before finally looking it up and learning it. I wish I’d done so well before.

I most commonly use it to make backup files

$ cp /path/to/some/file !#:1.bak
cp /path/to/some/file /path/to/some/file.bak

but once under the fingers it can be a very quick alternative to

7) !!:gs – The ‘Search and Replace’ One

This one searches across the referenced command, and replaces what’s in the first two / characters with what’s in the second two.

Say I want to tell the world that mys key does not work, and outputs f instead.

$ echo my f key doef not work
my f key doef not work

Then I realise that I was just wrongly hitting the f key by accident.

To replace all the fs with ses, I can type:

$ !!:gs/f /s /
echo my s key does not work
my s key does not work

It doesn’t just work on single characters. I can replace words or sentences too:

$ !!:gs/does/did/
echo my s key did not work
my s key did not work

Just to show you how these shortcuts can be combined, can you work out what these toenail clippings will output?

$ ping !#:0:gs/i/o
$ vi /tmp/!:0.txt
$ ls !$:h
$ cd !-2:h
$ touch !$!-3:$ !! !$.txt
$ cat !:1-$

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