How To Remove Onlyspl Cahracters From Variable In Shell Script

Shell Programming

Hey there! Today, I’m going to show you how to remove special characters from a variable in a shell script. This is a common task in scripting, and it’s useful to know how to clean up strings for further processing. Let’s dive in and learn how to do it!

Understanding the Problem

First off, what do we mean by special characters? In this context, special characters are those that are not alphanumeric or whitespace. Examples include symbols like !, @, #, $, %, and so on. These characters can sometimes cause issues when processing strings, so it’s often necessary to remove them.

Using Parameter Expansion

One way to remove special characters from a variable in a shell script is to use parameter expansion with pattern removal. Let’s say we have a variable myVar that contains the string we want to clean up. We can use the following syntax to remove all non-alphanumeric characters:


This command uses the // pattern to replace all non-alphanumeric characters with an empty string, effectively removing them from the original variable. This is a powerful and concise way to clean up a string in a shell script.

Using Sed

Another method to remove special characters is to use the sed command. This method offers a bit more flexibility, especially if you need to remove specific characters or patterns from the string.

cleanVar=$(echo $myVar | sed 's/[^a-zA-Z0-9]//g')

Here, we’re using sed to substitute all non-alphanumeric characters with an empty string. The g at the end of the command ensures that all occurrences are replaced, not just the first one.


There you have it! Removing special characters from a variable in a shell script is a fundamental skill that can come in handy in many scripting tasks. Whether you prefer the succinctness of parameter expansion or the flexibility of sed, these methods will help you clean up strings and prepare them for further processing.