How to loop through an array in Bash?

Looping Through Arrays in Bash

In Bash, the shell scripting language, you can loop through an array in several ways. Here are the most common methods:

Using a for Loop

The simplest way to loop through an array in Bash is by using a for loop. Here's an example:

my_array=(apple banana cherry)

for item in "${my_array[@]}"; do
    echo "$item"
done

This will output:

apple
banana
cherry

The ${my_array[@]} syntax is used to access all the elements of the array. The do and done keywords define the loop block.

Using a for Loop with Index

You can also loop through an array using the index of each element. Here's an example:

my_array=(apple banana cherry)

for i in "${!my_array[@]}"; do
    echo "${my_array[$i]}"
done

This will output the same result as the previous example:

apple
banana
cherry

The ${!my_array[@]} syntax is used to get the indices of the array elements, and then we can access each element using the index ${my_array[$i]}.

Using a while Loop

You can also use a while loop to iterate through an array. Here's an example:

my_array=(apple banana cherry)
i=0

while [ $i -lt ${#my_array[@]} ]; do
    echo "${my_array[$i]}"
    i=$((i+1))
done

This will also output the same result as the previous examples:

apple
banana
cherry

In this case, we use a variable i to keep track of the current index, and we check the length of the array ${#my_array[@]} to determine the loop condition.

Visualizing the Concepts

Here's a Mermaid diagram that illustrates the different ways of looping through an array in Bash:

In summary, Bash provides several ways to loop through an array, each with its own advantages and use cases. The choice of method depends on your specific needs and the requirements of your script.