Sort

In this lesson, you’ll learn how to append elements to a Bash array and then sort that array using standard Unix utilities. We’ll cover:

Appending items with the += notation
Sorting array elements by printing each one on a new line
Capturing sorted output in a new array for easy comparison

1. Appending Elements with `+=`

Bash arrays support the += operator to add one or more items at the end of an existing array. Here’s an example:

#!/usr/bin/env bash
declare -a array=("One" "Two" "Three")
echo "Original array: ${array[@]}"

# Append three more elements
array+=("Four" "Five" "Six")
echo "After appending: ${array[@]}"

Save this as example2.sh and run:

$ chmod +x example2.sh
$ ./example2.sh
Original array: One Two Three
After appending: One Two Three Four Five Six

2. Sorting an Array with `printf` & `sort`

Bash doesn’t have a built-in array sort, but you can leverage the Unix sort command. Since sort expects one item per line, use printf to split space-separated elements:

Do not enclose each item in quotes (e.g., "a" "b"), or printf will treat them as single arguments and won’t split them into lines.

# Example: sorting letters
printf "%s\n" d a g h i f | sort

Output:

a
d
f
g
h
i

You can apply the same method to numeric arrays:

#!/usr/bin/env bash
declare -a nums=(4 2 0 6 8 1)

# Print each element on its own line and pipe to sort
printf "%s\n" "${nums[@]}" | sort

Running sort_numbers.sh:

$ chmod +x sort_numbers.sh
$ ./sort_numbers.sh
0
1
2
4
6
8

3. Displaying Unsorted and Sorted Arrays

To compare the original and sorted array side by side, capture the sorted output in a new array via command substitution:

#!/usr/bin/env bash
declare -a nums=(4 2 0 6 8 1)

# Display the unsorted array
echo "Unsorted array: ${nums[@]}"

# Sort and capture in a new array
sorted_nums=($(printf "%s\n" "${nums[@]}" | sort))

# Display the sorted array
echo "Sorted array: ${sorted_nums[@]}"

Running sort_ex2.sh produces:

$ chmod +x sort_ex2.sh
$ ./sort_ex2.sh
Unsorted array: 4 2 0 6 8 1
Sorted array: 0 1 2 4 6 8

The image shows a comparison between an unsorted array (4, 2, 0, 6, 8, 1) and its sorted version (0, 1, 2, 4, 6, 8) with a lightbulb icon above.

Summary

Task	Command Example
Append elements	`array+=("item1" "item2")`
Sort an array	`printf "%s\n" "${array[@]}" \| sort`
Capture sorted output	`sorted=( $(printf "%s\n" "${array[@]}" \| sort) )`

Introduction

Conventions

Refresher

Streams

Expansions - Part One

Globs

Expansions - Part Two

Special Shell Variables

Arrays

Good Practices applied

awk

sed

1. Appending Elements with `+=`

2. Sorting an Array with `printf` & `sort`

3. Displaying Unsorted and Sorted Arrays

Summary

Links and References

Watch Video

​1. Appending Elements with +=

​2. Sorting an Array with printf & sort

​3. Displaying Unsorted and Sorted Arrays

​Summary

​Links and References

Watch Video

1. Appending Elements with `+=`

2. Sorting an Array with `printf` & `sort`

3. Displaying Unsorted and Sorted Arrays

Summary

Links and References