Bash (Bourne Again SHell) is a popular Unix shell and command language that is widely used in Linux systems. One of the powerful features of Bash is its ability to execute repetitive tasks efficiently using loops. In this article, we will explore the different types of loops available in Bash and how to use them effectively.

1. for loop

The for loop in Bash allows you to iterate over a list of items and execute a set of commands for each item. It follows the syntax:

for variable in list
do
    command(s)
done

Here’s an example that prints numbers from 1 to 5:

for i in 1 2 3 4 5
do
    echo $i
done

You can also use a variable as the list of items. For example, the following loop prints each item in an array:

fruits=("apple" "banana" "cherry" "date")

for fruit in ${fruits[@]}
do
    echo $fruit
done

2. while loop

A while loop executes a set of commands as long as a specified condition is true. It follows the syntax:

while condition
do
    command(s)
done

Here’s an example that prints numbers from 1 to 5 using a while loop:

counter=1

while [ $counter -le 5 ]
do
    echo $counter
    counter=$((counter+1))
done

3. until loop

An until loop is similar to a while loop, except that it keeps executing a set of commands until a specified condition becomes true. It follows the syntax:

until condition
do
    command(s)
done

Here’s an example that prints numbers from 1 to 5 using an until loop:

counter=1

until [ $counter -gt 5 ]
do
    echo $counter
    counter=$((counter+1))
done

Conclusion

Loops are an essential part of scripting languages like Bash, allowing you to automate repetitive tasks and improve efficiency. The for, while, and until loops provide different ways to iterate over data and perform actions. By leveraging the power of loops in Bash, you can write more robust and effective scripts.

So, start incorporating loops in your Bash scripts and enjoy the benefits of automated repetitive tasks!