How to Split String Into Array in Bash

1. Using the read Command to Split a String Into an Array in Bash
2. Using the tr Command to Split a String Into an Array in Bash
3. Using Parameter Expansion to Split a String Into an Array in Bash

This tutorial explains splitting a string into an array in bash using the read command, the tr command, and parameter expansion.

Using the read Command to Split a String Into an Array in Bash

The read command is a built-in command on Linux systems.

It is used to read the content of a line into a variable. It also splits words of a string that is assigned to a shell variable.

In the script below, the variable $addrs string is passed to the read command. The IFS sets the delimiter that acts as a word boundary on the string variable.

This means the - is the word boundary in our case. The -a option tells the read command to store the words that have been split into an array, while the -r option tells the read command to treat any escape characters as they are and not interpret them.

The words that have been split are stored into the ip_array variable. To access the individual elements inside the array, we use this syntax, ${array name[index]}.

In the script below, ip_array is the array name, and 0 is the index denoting the first element in the array.

#!/usr/bin/env bash

addrs="192.168.8.1,192.168.8.2,192.168.8.3,192.168.8.4"

IFS=',' read -ra ip_array <<< "$addrs"

printf "${ip_array[0]}\n"

The output displays the first element in the array.

192.168.8.1

The script below adds a for loop iterating through the array and prints all the elements using the echo command.

#!/usr/bin/env bash

addrs="192.168.8.1,192.168.8.2,192.168.8.3,192.168.8.4"

IFS=',' read -r -a ip_array <<< "$addrs"

for ip in "${ip_array[@]}"
do
    echo "$ip"
done

The output below displays all the elements that are inside the array.

192.168.8.1
192.168.8.2
192.168.8.3
192.168.8.4

Using the tr Command to Split a String Into an Array in Bash

The tr command is a short form for translate.

It translates, deletes, and squeezes characters from the standard input and writes the results to the standard output. It is a useful command for manipulating text on the command line or in a bash script.

It can be used to remove repeated characters, convert lowercase to uppercase, and replace characters.

In the bash script below, the echo command pipes the string variable, $addrs, to the tr command, which splits the string variable on a delimiter, ;. Once the string has been split, the values are assigned to the ip_addrs array.

The for loop iterates through the $ip_addrs array and prints out all the values using the printf command.

#!/bin/bash

addrs="192.168.8.1,192.168.8.2,192.168.8.3,192.168.8.4"

ip_addrs=(`echo $addrs | tr ',' ' '`)

for ip in "${ip_addrs[@]}"
do
    printf "$ip\n"
done

The output below displays all the elements that are inside the array.

192.168.8.1
192.168.8.2
192.168.8.3
192.168.8.4

Using Parameter Expansion to Split a String Into an Array in Bash

The script below uses parameter expansion to search and replace characters.

The syntax used for for parameter expansion is ${variable//search/replace}. It searches for a pattern that matches search in the variable and replaces it with the replace.

In our case, the script searches for the pattern , and replaces it with a white space in the $addrs string variable. The parenthesis around ${addrs//-/ } are used to define an array of the new string, called ip_array.

We use the for loop to iterate over all the elements of the ip_array and display them using the echo command.

#!/bin/bash

addrs="192.168.8.1,192.168.8.2,192.168.8.3,192.168.8.4"

set -f
ip_array=(${addrs//,/ })

for ip in "${!ip_array[@]}"
do
    echo "[$ip] ${ip_array[ip]}"
done

The output below displays all the elements that are inside the array.

[0] 192.168.8.1
[1] 192.168.8.2
[2] 192.168.8.3
[3] 192.168.8.4