Bash: If, Else If, Else Examples

In this Linux Hint tutorial we will teach Bash scripting conditionals using IF, ELIF and ELSE commands. The IF condition is the most basic way to take conditional action in a bash scripts so its important to have a firm grasp on its syntax and options to be productive. When using IF conditions in Bash, you can optionally introduce ELIF conditions that will provide different actions depending on which of a group of conditions is TRUE. Additionally the ELSE condition can be optionally included, which will provide code to execute if none of the conditions in the group is met.

Specific Examples Shown in this Article Include:

1. Example 1: If statement in bash on string equality
2. Example 2: If statement in bash on number equality
3. Example 3: If statement in bash on less than a number
4. Example 4: If statement in bash with logical AND operator
5. Example 5: If statement in bash with logical OR operator
6. Example 6: Elif condition in bash
7. Example 7: If Else Statement in Bash Scripting

General Syntax of Bash IF ELIF ELSE

Below is the general syntax of IF ELIF and ELSE in bash:

Note: In the above general syntax that you can include zero, one or multiple ELIF conditions in the code block and the ELSE condition is optional.

Construction of the actual conditions has many options because the syntax of bash has so many different features and options, but a very basic template for your bash scripts would be to use the [[ double brack syntax as shown in the general syntax example and specific examples below.

Note also: That depending on your code formatting aesthetics you may like the then on the same line of the conditions or you may opt to put it in the next line as shown below:

Now lets show specific examples of the basic variations of the IF ELIF and ELSE conditions in working examples below.

Example 1: If statement in bash on string equality

In this example above we use the basic IF condition with a single test of string equality and then print some output in case the condition is true based on input from the user. Note, you can place the THEN statement on the next line if you prefer that style. See the example output below:

Example 2: If statement in bash on number equality

In this example above, again we do a simple IF condition but in this case we demonstrate how to do a test comparison on numeric values. You can see the output below with both the matching and non matching conditions:

Example 3: If statement in bash on less than a number

In addition to -eq for equality you can also try -lt -le -gt -ge test conditions for less than, less than or equal, greater than or greater then or equal respectively. Below is a similar example with less then operator -lt:

Output for this script will be able to test if the input is less than 100 and run specific code on that condition:

Example 4: If statement in bash with logical AND operator

This example will show how to combine multiple conditions with a logical AND condition. You can also use logical OR conditions in your IF statement constructs. Logical AND in bash code is written with double ampersand &&. Below is an example of logical AND in a bash IF condition:

We will test this with various outputs to prove that only if both the first and the second condition are true the output will be printed:

Example 5: If statement in bash with logical OR operator

Logical OR in bash scripts is written with double vertical bars ||. Let’s try the previous example again with a slight variation to test out an example of the logical OR operator:

In this example the logical OR operator combines two conditions and only one of them or both can be true for the condition to be overall true and the code to execute. We also demonstrate the -ge operator for greater or equal numeric comparison in the above example. The script is working as expected in the output below:

Example 6: elif condition in bash

We will now provide an example for multiple if conditions in the code block with ELIF. You can have zero, one, or multipe ELIF conditions in a code block. For this example we will provide two ELIF conditions as a demonstration, but you can use any number of ELIF blocks in practice.

We will test this code with a variety of numbers to demonstrate which if or ELIF condition is triggered:

Example 7: If Else Statement in Bash Scripting

We will now demonstrate the ELSE condition. The ELSE condition is used in the case where the IF condition or all the ELIF conditions do not exist then the ELSE condition will be used and the code in the ELSE condition will be executed. Let’s add an example of ELSE condition to the previous example but to be clear ELIF is not required to leverage the ELSE condition. The ELSE condition can be used with a IF condition and no ELIF condition.

Let’s test the example code with a simple test case that should fall into the ELSE condition:

CONCLUSION

We have seen how to use IF, ELIF and ELSE conditions to form conditional execution in many combinations in bash scripts and bash programs. For next steps you can study test conditions and the variations and varieties available for testing a condition. You can also consider the bash case statement as an alternate for conditional logic in bash scripts. Finally the GNU Bash Reference Manual is a good source of truth when looking for exact syntax details.