A Beginner's Guide to While Loops in Shell Scripting

Shell scripting is a powerful tool that allows us to automate tasks on a Unix or Linux system.

It is a scripting language that is interpreted by the Unix or Linux shell. One of the most important constructs in shell scripting is the loop.

The loop is used to repeat a set of commands multiple times. There are different types of loops available in shell scripting, such as for loop, while loop, until loop, etc. In this article, we will focus on the while loop in shell scripting.

What is a While Loop?

A while loop is a control flow statement that repeatedly executes a set of commands as long as the specified condition is true.

The while loop is useful when you want to repeat a set of commands a variable number of times, based on some condition.

The syntax of a while loop is as follows:

while [ condition ]
do
   commands
done

In the above syntax, the condition is evaluated before each iteration of the loop. If the condition is true, the commands inside the loop are executed. Once the commands are executed, the condition is evaluated again, and if it is still true, the commands are executed again. This process continues until the condition becomes false.

Let's take a look at some examples of while loops in shell scripting.

Example : Print Numbers from 1 to 10

In this example, we will use a while loop to print numbers from 1 to 10.

#!/bin/bash

# Set the counter to 1
counter=1

# Loop until the counter is greater than 10
while [ $counter -le 10 ]
do
   echo $counter
   # Increment the counter
   counter=$((counter+1))
done

In the above example, we first set the counter variable to 1.

Then we use a while loop to print the value of the counter variable.

Inside the loop, we also increment the counter variable by 1.

The loop continues until the value of the counter variable is greater than 10.

Conclusion:

In this article, we have learned about the while loop in shell scripting.

We have seen how to use a while loop to repeat a set of commands as long as a specified condition is true.