Bash alias is said to be a technique used within the Linux system as an easy alternative for bash commands to override difficult ones with fresh ones. In other words, an alias is used within bash users to get easier hands-on terminal commands to exchange difficult commands. Many of the bash users among us find some bash commands difficult to remember that they feel a need for easier ones. Alias is basically for those users.
Today’s article will discuss different ways to create simple bash alias with and without arguments and parameters. So, let’s get started with opening the shell terminal using “Ctrl+Alt+T” after login in from the Ubuntu 20.04 Linux operating system.
Make Simple Bash Alias
On the daily basis, we use many bash commands in the shell of the Linux system. One of them is the list command to list all the files and folders within the home directory as below.
Another command shows the same list but with little more information regarding files and folders e.g. privileges, date of creation, user, and group to which it belongs.
For example, you don’t remember the command “ls –l”, so you want to make an easier one with an alias. Hence, we will be using the below simple alias commands to create an “ls” alias in exchange for “ls –l”.
When we use the “ls” command, it will show the output for what it shows for “ls –l”. This means the terminal forgets what “ls” used to show us before making an alias.
To undo the alias, try the below query.
Now, while running the same “ls” query, it shows the original output as it was shown before the making of the alias
Bash Alias with Arguments and Parameters
Bash users need to understand that alias cannot take arguments and parameters. But we can use functions to take arguments and parameters while using alias commands. Firstly, we need to see what content we have in the files we are using in our bash code to make an alias. So, we will be using two files e.g. test.sh and file.sh in the alias code. We will be opening the “test.sh” file within the terminal to see its contents via the “cat” query as below. You can have a glance that it contains simple text providing information regarding a user “aqsayasin”. Quit the file using “Ctrl+X”.
Let’s now open the other file “file.sh” to see its contents using the same “cat” instruction in the shell as beneath. You can see from the output that the file is already empty so we need to fill it with some data.
Let’s create an example of a function to see how the alias in bash can be created using arguments and parameters. As we know that, the alias never accepts arguments or parameters, hence, we will be using the function to do so. We will write our commands taking arguments and behaving like an alias within the function. So within the terminal shell, we have created a function “func()” and added the commands for “move” and “copy” contents of one argument parameter to another.
The parameter argument “$1” represents the first file having no contents and “$2” represents the file having content in it at the time of writing the code. The “mv” command is behaving like an alias moving the “$1” argument file “$1.txt” parameter. This means another file will be created having the same data. The “cp” command is behaving like an alias taking the first argument e.g. “test.sh” and copy its contents to other arguments which would be an empty file “file.sh”. In the last, the function has been closed.
Let’s test this functional argument alias within the shell by simply calling the function with passing two arguments as file names. So, we have used “file.sh” as a parameter value to the argument “$1” and “test.sh” as a parameter value to the argument “$2”. Try out the query below to make the alias worked as mentioned in the function “func”.
As the “file.sh” has been passed to the argument $1 as a parametric value, according to the bash code, it must now contain the data of file “test.sh” which represents the argument $2 as per the “cp” command. Hence, whenever we checked or displayed the contents of a file “file.sh” via the cat query, it shows that the file has been filled with the data that was initially a content of a file “test.sh”. Now, both the bash files have the same data within them as the output shows.
According to the “mv” statement used in the function “func” behaving like an alias taking arguments, must now move the “$1” value to the “$1.txt” argument. In this alias command, “$1” represents “file.sh” and “$1.txt” represents a new file to be created which will have the same data and name with a different extension than file.sh.
So, when we have checked up on the newly created file “file.sh.txt”, we have found that it also contains the same data as the file “file.sh” have via the alias query “mv”. It simply moves the file.sh to the file.sh.txt completely. For this purpose, we have tried the query “cat” as below.
Create Alias Within a Function
Here is a simple illustration of making an alias within some function. It will work the same as it worked for the simple alias creation above. So, we have created a function “test()” and created 6 alias in exchange for 6 difficult commands of bash. Try this code in the shell and see how it works.
Firstly, we have listed the files and folders of the home directory to be used further.
As per the alias created within the function executed above in the terminal, these queries must work now. First, we are going to see how the previous difficult queries worked. We have tried the “remove” query to delete file “one.sh” from the list above. It will confirm your action by asking you to remove this file. Tap “y” to remove it.
Upon checking the list again, we found that the file has been deleted.
Let’s check the alias command now to remove another file. So, we have tried the alias “rm” to remove “file.sh”. After checking, we found that the alias worked the same as the previous query.
Use the alias “mv” to move the file “new.sh” to a “Documents” folder with the below query.
When we have navigated towards the “Documents” folder and listed its contents, we have found that the file “new.sh” has been successfully moved here with the usage of the “mv” alias.
In this guide, we have discussed how to make a simple alias within the shell and how to make a bash alias with arguments and parameters while using functions. We have also discussed how to use an alias within a function without taking arguments or parameters and how to uncover these alias as well. We believe this article is completely able to help you a lot while you have been working on bash alias with arguments and parameters.