The bang operator

#osx

#apple

#screencast

#history

As mentioned back in July with, Top 10 shell commands you currently use, I showed how the history command displays the command history list with line numbers. Here is a sample of the last 5 lines of history on my local system:

1786  rake post title="The-bang-operator"
1787  vi \_posts/2013-12-22-the-bang-operator.md
1788  man history
1789  help history
1790  fg

We can make use of our command history more effectively by using the shell “bang operator”.

SHELL ! (AKA BANG OPERATOR)

The line numbers shown in history output are used as command identifiers. Therefore, if I wanted to run the rake command shown above, all I would need to do is specify the bang operator provided by the shell, followed immediately by the number associated with the command:

!1786

Alternatively, I could also use the bang operator before a command:

!rake

This allows you to run previous commands quickly without having to remember all of the options, switches or arguments that were passed to the command.

USING :P WITH THE BANG OPERATOR

However, what if the command you want is far back in your history and you do not want to run history and scroll through a heavy amount of output? One solution is to use :p with the bang operator, which allows you to recall that last command, but without running it:

!rake:p
rake post title="The-bang-operator"

This is useful because sometimes you have other commands that might match the command pattern you specify with the bang operator, yet those commands might be unsafe to run. In other words, what if the last rake command I ran did something destructive? By using :p, it allows you to recall the command safely and then decide if it is safe to run.

“LEARNING THE UNIX COMMAND LINE ON OS X” SCREENCAST

Since my last post, I have produced a screencast called, “Learning the UNIX command line on OS X”, which contains over 50 lectures and 3.5 hours of content. It is now available for purchase on Udemy at https://www.udemy.com/learning-the-unix-command-line-on-os-x/.