How to Use Bash Continue with “while” Loop [7 Examples]

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Continue statement in bash while loop skips the current iteration and jumps to the next iteration. It is a control statement that allows programmers to skip any specific iterations during loop execution. In this article, I will explore the process of using the continue statement in a while loop.

7 Examples of “while” Loop with Continue Statement

While loop with continue statement in Bash can print a series of numbers considering user input or specific choice, process a specific type of files. Here, I will demonstrate 7 examples of these.

1. Skipping Iteration with Continue Statement in “while” Loop

While loop executes the commands inside the block as long as the condition is true. Use the continue statement with while loop in Bash to skip any iteration. Here is a bash script to print numbers from 0 to 5, skipping 2:

#!/bin/bash
a=0
while [[ $a -lt 5 ]]; do
    ((a++))
    if [[ "$a" == '2' ]]; then
        continue
    fi
    echo "Number: $a"
done
echo "Done!"

2. Finding Even Numbers

Even numbers are those numbers whose remainder after dividing by 2 is zero. While loop iterates as long as the loop condition is true. Keeping the logic inside the if clause inside the loop, even numbers can easily be determined. Here is a bash script to find even numbers from an iteration list:

#!/bin/bash
a=1
while [ $a -le 10 ]; do
    if [ $((a % 2)) -eq 1 ]; then
        #Skip odd numbers
        a=$((a + 1))
        continue
    fi
    echo $a
    a=$((a + 1))
done

3. Skipping a Specific Type of File

While loop can iterate through all files inside a directory. Keeping a specific condition inside the if statement of the loop enables programmers to skip a specific type of file. Here is a bash script that prints all the files inside the directory except txt files:

#!/bin/bash
dir="/home/susmit/Backup"
counter=1
while [ $counter -le "$(ls -1 "$dir" | wc -l)" ]; do
    file=$(ls -1 "$dir" | sed -n "${counter}p")
    if [ "${file##*.}" == "txt" ]; then
        ((counter++))
        continue
    fi
    echo "$dir/$file"
    ((counter++))
done

4. Skipping Empty Lines in a File

While loop can iterate through a large file line by line. Skipping empty lines while printing file content on the terminal eases users’ task of going through files effectively. Here is a bash script that iterates through each line of a file and prints them, skipping the empty lines:

#!/bin/bash
while IFS= read -r line; do
    if [ -z "$line" ]; then
    continue
    fi
    echo "Processing line: $line"
done < "input.txt"

5. Skipping Iteration Based on User Input

While loop can print a series of numbers considering the input from users while iterating. The read command can read user input and then incorporate the input inside the condition of the if statement, which can decide what to print and what not to print. Here is how to do this:

#!/bin/bash
c=1
while [ $c -le 5 ]; do
    read -p "Do you want to accept $c? (y/n): " choice
    if [ "$choice" == "n" ]; then
        ((c++))
        continue
    fi
    echo "$c"
    ((c++))
done

6. Skipping Specific Values in an Array

While loop can iterate through an array with the help of an array index. Put the specified condition inside the condition block of the if statement to skip a specific element of an array. Here is a bash script that will print all the array elements except “Mike”:

#!/bin/bash
index=0
val=("Wade" "Warner" "Mike" "Lee")
while [ $index -lt ${#val[@]} ];do
    current_val="${val[$index]}"
    if [ "$current_val" == "Mike" ]; then
        ((index++))
        continue
    fi
    echo "$current_val"
    ((index++))
done

7. Concurrent Image Conversion

While loop in Bash can iterate through a list of photos with the help of array indexing, then, convert the image format from JPEG to PNG using the convert command. Here is a bash script where while loop will iterate over all JPEG files inside the current directory and convert them to PNG format:

#!/bin/bash
echo "Converting JPEG files to PNG concurrently:"

convert_image() {
    local image="$1"
    echo "Converting: $image"
    convert "$image" "${image%.jpg}.png"
}

image_list=(*.jpg)
total_images=${#image_list[@]}
counter=0
while [ $counter -lt $total_images ]; do
    current_image="${image_list[$counter]}"
    convert_image "$current_image" &
    counter=$((counter + 1))
    done
wait
echo "Conversion complete."

Printing a Series of Numbers Then Exit

While loop can print a series of numbers, and it can be terminated with the break command. Here is a bash script that prints numbers from 0 to 3 and then terminates:

#!/bin/bash
a=0
while [[ $a -lt 5 ]]
do
    echo "Value: $a"
    ((a++))
    if [[ $a -eq 3 ]]; then
       break
    fi
done
echo "Done!"

Conclusion

In conclusion, using the continue command in the bash while loop will make the bash script more versatile while iterating. It will give the control over which iteration entity to process and which to skip. This article will help the learners to use the continue statement in the while loop effectively.

People Also Ask

What does continue in Bash do?

The continue command in bash skips the current iterations and jumps to the next iteration. It does not execute the subsequent commands after the continue statement and jumps to the next iteration.

How do you break out of a while loop in Bash?

To break out of a while loop in Bash, use the break command. It will terminate the loop and go to subsequent commands after the loop. The break command is a control statement that allows the termination of a loop prematurely.

What is the difference between break and continue in Bash script?

The break command and the continue command are both control statements. The continue statement skips the current iteration and jumps to the next iteration without executing the commands after the continue statement. On the other hand, the break statement terminates loop execution and jumps to the subsequent command after the loop.

Can a while loop have multiple conditions?

Yes, a while loop can have multiple conditions. You could use logical AND (&&), OR (||) to combine multiple conditions inside the condition block of a while loop.

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