Create custom Linux Commands

Sometimes I get really bored of typing the same commands over and over again. For example, when building my Jekyll Blog into a certain folder (bundle exec jekyll build --destination /var/www --watch &) or moving to a specific folder just to perform a git pull.

A great way to handle this problem is to create your own shell scripts, which can be executed from any location, just like apt-get.
It’s also possible to pass parameters to these custom commands. For example: apt-get install ruby.

Create a Script Directory

First of all, we need to find a good location to store all of our scripts.
I usually create a folder named shell-scripts in the /var directory:

$ cd /var
$ sudo mkdir shell-scripts

All files in this folder need to be executable and editable (we don’t always want to use sudo to edit our scripts):

$ sudo chmod -R 777 /shell-scripts

Everybody is now able to execute everything in the folder /var/shell-scripts.

Customize PATH Locations

After creating the directory, we have to make sure our system knows the location of these scripts.
That allows us to execute them in any directory we are currently in.
Open the .bashrc file with any editor you like (I use the Vi-Editor - Tutorial here):

$ sudo vi ~/.bashrc

Now we’re going to add our freshly created shell-scripts folder to the PATH locations.
Append the following content:

# global shell scripts
export PATH=$PATH:/var/shell-scripts

Save and close the file.
To make sure the system reloads the file, you can either relog your user or proceed with the following command:

$ source ~/.bashrc

Add Path to ‘sudo’ Location

There is another location file we have to modify if we want to execute our shell scripts with sudo permissions.
This step is optional if you want to create only non-root commands.

$ sudo visudo

Search for secure-path= and append our folder:

Defaults secure-path="... :/var/shell-scripts"

Save and close the file.

Write a Shell Script

Finally, we are ready to deploy our first custom command.
In this example, we want to perform a git pull request in a folder named /etc/gitrepo just by typing pullgit anywhere on the system.

Head over to your shell-scripts folder and create a file with 777 permissions.
The name of the file will be the command you have to type in the console later on!

$ cd /var/shell-scripts
$ touch pullgit
$ sudo chmod 777 pullgit

Open the file with your preferred editor:

$ vi pullgit

Write everything that should be executed with your custom command.
In our example, this will be a really short script:

#!/bin/bash
cd /etc/gitrepo
git pull

Save and close the file.
Just repeat this chapter for all of your further custom commands.

Passing Parameters

echo firstparam echo secondparam It is also possible to pass parameters to our commands (shell scripts).
A sample code with two passed parameters would look like this:

#!/bin/bash
firstparam="$1"
secondparam="$2"
echo $firstparam
echo $secondparam

Usage:

$ testscript hello world
hello
world

Use your Command

Once we are done setting up the locations and writing our scripts, it’s time to try everything out!
It doesn’t matter which directory you are in—just type the name of the file you created.
In our example, it would be:

$ pullgit