How to Remove First/Last Characters from a Variable in a Shell Script

When working on a Bash or Fish script, there may come a time when you need to remove the first or last few characters from a string variable. While this task might seem straightforward, it can sometimes take longer than expected to figure out the correct solution. In this blog post, we’ll explore how to remove the first or last characters from a variable in a shell script.

Removing the First Characters

To remove the first n characters from a string variable, you can use the cut command in combination with command substitution. Here’s an example:

#!/bin/sh
original="my original string"
result=$(echo $original | cut -c10-) # cut first 10 characters
echo $result

In this script, we set the original variable to the string “my original string”. Then, we use the cut command with the -c option to specify the characters to cut. In this case, we cut from the 10th character until the end of the string. Finally, we assign the resulting string to the result variable and echo it.

Removing the Last Characters

Similarly, if you want to remove the last n characters from a string variable, you can use the rev command along with cut and command substitution. Here’s an example:

#!/bin/sh
original="my original string"
result=$(echo $original | rev | cut -c10- | rev) # cut last 10 characters
echo $result

In this script, we use rev to reverse the string before cutting. Then, we use cut as before, cutting from the 10th character until the end. Finally, we reverse the string again using rev and assign the result to the result variable.

By following these approaches, you can remove the first or last characters from a variable in a shell script. Make sure to adjust the number of characters to cut based on your specific requirement.

tags: [“shell scripting”, “Bash”, “Fish”, “variable manipulation”]