In Bash scripting, the continue and break keywords are control flow statements that allow you to alter the execution of loops. They are typically used within loop structures to skip specific iterations or completely exit a loop when certain conditions are met.

continue keyword:

The continue keyword is used to skip the current iteration of a loop and move on to the next one. It is particularly useful when you want to bypass certain iterations based on specific conditions.

Here’s an example that demonstrates the usage of this keyword.

 1#!/bin/bash
 2
 3for num in {1..10}
 4do
 5    if ((num % 2 == 1))
 6    then
 7        continue
 8    fi
 9    echo $num
10done

Explanation:

In this script, we use a for loop to iterate from 1 to 10. The condition ((num % 2 == 1)) checks if the current number num is not divisible by 2, that is if the number is odd. If this condition evaluates to true, (if num is odd) the continue keyword will be executed which will skip that particular iteration. If the condition evaluates to false, we print out the value of num.

Output:

12
24
36
48
510

break keyword:

The “break” keyword allows you to exit out of a loop completely when certain conditions are met. It can be useful when you need to terminate a loop prematurely.

 1#!/bin/bash
 2
 3for num in {1..10}
 4do
 5    if ((num % 4 == 0))
 6    then
 7        break
 8    fi
 9    echo $num
10done

Output:

1
2
3

Above code is similar to previous one. In this case as soon as we encounter the value which is divisible by 4, we exit the iteration. The first value will be 4, so the output is 1 to 3.

This is quite useful when we are creating some interactive script where user can input data.

 1#!/bin/bash
 2echo "Please talk to me..."
 3while true
 4do
 5	read input
 6	case $input in
 7		hello)
 8			echo "Hello there!"
 9			;;
10		bye)
11			echo "See you again!"
12			break
13			;;
14		*)
15			echo "Sorry, I don't understand"
16			;;
17	esac
18done

Explanation:

In above script, we have infinite loop with while true. This loop never terminate itself. Inside the while loop, we accept user input and store in a variable input. We then perform conditional checks on this variable value and check if it is string ‘hello’, ‘bye’ or something else using case statements. We perform action corresponding to each of those. If it’s ‘bye’, then we want to exit the while loop, so we have break statement in that conditional check.

Output:

bash script.sh
Please talk to me...
hello
Hello there!
how are you?
Sorry, I don't understand
bye
See you again!