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Fun with Bash expansions

28 Nov 2018 · Cody Reichert

Using bash a lot in your daily work can be monotonous, but you can have more fun with bash expansions! Here’s a few things I picked up over the years that are helpful for being more efficient on the command line:

Repeat the last command

To run the previous command again, you can of course type up. But what’s more fun is using !!.

$ echo "Hello, world!"
Hello, world!
$ !!
Hello, world!

Pro-tip 1 prepend/append to the last command

You can add more arguments before and after the last command like this:

$ !! <and more things here>

Pro-tip 2 edit the last command before executing

There’s an option you can set in your bash settings that allows you to edit the command before executing it:

# in your .bashrc
shopt -s histverify

Now when you type !!, you get this behavior:

$ !!
$ echo "Hello, world!" # you can edit this command before executing it!

Replace part of the last command

Another great bash features is the ability to replace part of the last command, and then re-execute it. To do this, you use the ^before^after syntax:

$ echo "Hello, worl!"
Hello, worl! # <-- woops, there's a typo. Let's fix it!
$ ^worl^world
Hello, world!

Nice!

Execute a command in the bash history

One common use-case is to execute a command that has been run before. To do this, you need to know the number of the command by looking at the output of history:

$ history
98 echo "Hello, worl!"
99 echo "Hello, world!"

To run command number 99 again, prefix it with a !:

$ !99
Hello, world!

More fun with bash

I have a few more tricks up my bash sleeve that I’ll add to this post, but these are by far the most useful and common commands. Have any expansions that I should add to the list? Hit me up via any of the methods below.

:: Cody Reichert

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