How to use arrays in Bash

When you want to use multiple data using a single variable in any programming language, you have to use array variables. The list of data can be assigned and used using an array variable. Bash is a weakly typed language that does not require defining any data type for declaring the variable. Array declaration in bash is a little bit different from other standard programming languages. Two types of the array can be declared in bash. Numeric array and associative array. If the index of an array is numeric, then it is called a numeric array, and if the index of an array is a string, it is called an associative array. How you can declare a numeric array, associative array, and iterate elements of the array using for loop are described with examples in this tutorial.

Example-1: Numeric Array Declaration:

The default index of an array is numeric, and all values are taken as a string value. A simple numeric array of 5 string values are declared here. The echo command is used here to print each array values separately. If you want to print all values of the array by single echo command, then the “*” symbol has to be used in the array’s index. Create a bash file with the following script that shows two ways to declare an array in the bash script.

Output:

The following output will appear after executing the above script.

Example-2: Associative Array Declaration:

Each index of the array needs to be declared separately in the associative array. Create a bash file with the following script to know the use of associative array in bash. An associative array of 4 elements is declared in the following examples. The values of the array can be printed by using each index separately, like the previous example. Only the indexes of the associative array can be printed by using the “!” and “@” symbols.

Output:

The following output will appear after executing the above script.

Example-3: Reading Array values using for loop:

The total number of elements of any bash array can be counted by using the “#” and “*” symbols shown in the first part of the following example. Create a bash file with the following script to know the way of reading array values using the loop. For loop is commonly used to iterate the values of an array. You can also read array values and array indexes separately by using for loop. Different loops are used in the following example to read array indexes, array values, and both.

Output:
The following output will appear after executing the above script.

Example-4: Add element into the array

The new element can be added to an array in different ways. The way to add one or more elements using shorthand operator(+=) has shown in this example. Create a bash file with the following script to know how the new element can be inserted into an array.

Output:

The following output will appear after executing the above script.

Example-5: Delete an element from the array

The `unset` command is used to delete one or all elements from the array. Create a bash file with the following script to know how to delete one and all elements from a numeric array.

Output:

The following output will appear after executing the above script.

Example-6: Print the string value of multiple words

The value of the array requires to enclose with double quotes(“”) to add string value of multiple words into an array. Create a bash file with the following script where an associated array has initialized with the string values of multiple words.

Output:

The following output will appear after executing the above script.

Conclusion:

The array is used in programming for many purposes. Some common and very simple uses of the array in bash have been shown in this tutorial. After exercising the above examples, the basic concept of bash array will be cleared for the bash users, and they will be able to use bash array appropriately in their script.