Introduction to Arrays

Creating an Indexed Array

You create an array literal by listing values inside parentheses separated by spaces, e.g. fruits=(apple banana cherry). Bash automatically assigns indices starting at 0, so apple is at index 0, banana at index 1, and so on.

Example: Creating an Indexed Array

#!/bin/bash
fruits=(apple banana cherry)
echo "First fruit: ${fruits[0]}"
echo "Second fruit: ${fruits[1]}"

Accessing All Elements

${arr[@]} expands to every element of the array as separate words, which is what you want when looping over the contents. Using just $arr or ${arr} without an index only refers to element 0, a common beginner mistake.

Example: Accessing All Elements

#!/bin/bash
fruits=(apple banana cherry)
echo "All fruits: ${fruits[@]}"
echo "Just index 0 (via \$fruits): $fruits"

Array Length

${#arr[@]} gives the total number of elements currently stored in the array, which is useful for loop bounds or validation. This is different from ${#arr} or ${#arr[0]}, which give the character length of the first element's string.

Example: Array Length

#!/bin/bash
fruits=(apple banana cherry)
echo "Number of fruits: ${#fruits[@]}"
echo "Length of first element string: ${#fruits[0]}"

Appending to an Array

New elements can be added to the end of an array using the += operator with a parenthesized value list. This grows the array without needing to know its current length or rebuild it from scratch.

Warning: A full deep dive into arrays -- associative arrays, slicing, and more -- comes later in its own chapter.

Example: Appending to an Array

#!/bin/bash
fruits=(apple banana)
fruits+=(cherry)
fruits+=(date fig)
echo "Fruits now: ${fruits[@]}"
echo "Count: ${#fruits[@]}"