"The value of variable c is 15" "Unknown value" Checking String Variables. Bash if statement, if else statement, if elif else statement and nested if statement used to execute code based on a certain condition. Follow edited May 23 '17 at 10:30. The “if then elif then else fi” example mentioned in above can be converted to the nested if as shown below. They allow us to decide whether or not to run a piece of code based upon conditions that we may set. You saw, with examples, that you can build more complex statements : using elif and nested statements. 1. if statement 2. if else statement 3. if elif statement 4. This should give you a good understanding of conditional statements in Bash. Awesome! In this part of the bash beginner series, you will learn how to use conditional statements in your bash scripts to make it behave differently in different scenarios and cases. Following is the syntax of Else If statement in Bash Shell Scripting. You can place multiple if statement inside another if statement. Nested if statement 5. case statement Each type of statements is explained in this tutorial with an example. You can find further details in this question bash : Multiple Unary operators in if statement and some references given there like What is the difference between test, [ and [[ ?. This plays a different action or computation depending on whether the condition is true or false. In this example, we will look into two scenarios wherein one elif expression the condition evaluates to true and in the other to false. If elseis followed by an ALTERNATE-CONSEQUENT-COMMANDSlist, and the final command in the final ifor elifclause has a non-zero exit status, then … Check your inbox and click the link, Linux Command Line, Server, DevOps and Cloud, Great! The TEST-COMMANDSlist is executed, and if its return status is zero, the CONSEQUENT-COMMANDSlist is executed. If statement and else statement could be nested in bash. Moreover, the decision making statement is evaluating an In a conditional, you frequently have tasks to perform when the tested condition succeeds or fails. #!/bin/bash # Checking the first argument provided if [[ -n $1 ]] then echo "You provided a value" else echo "You should provide something" fi Conclusion. Enter a number: 88 Number is even. You can also use an if statement within another if statement. If the expression evaluates to true, statements of if block are executed. The shell can accommodate this with the if/then/else syntax. Bash way of writing Single and Multiline Comments, Salesforce Visualforce Interview Questions, Similar to Bash If statement, you may provide a single condition or multiple conditions after. An expression is associated with the if statement. This can be further enhanced to use if..elif..else and nested if so we will cover all such possible scenarios in this tutorial guide. Bash if Statement. Bash if-else statements are used to perform conditional tasks in the sequential flow of execution of statements. So the output will be Hy Aqsa Yasin in the terminal as shown in the below image. In the second ‘if else’ statement, the else condition will be executed since the criteria would be evaluated to false. The following types of conditional statements can be used in bash. As our string StdName has now a value Aqsa Yasin, and the -z string operator knows that the string is not null, so it executes the else part. Otherwise, you'll see an error like "unary operator expected". The first simply opens a if statement, the then introduces the what commands to execute if the statement condition was true section and the else introduces the what commands to execute if the statement condition was false section. In this example, we shall look into a scenario where there could be multiple conditions for elif (else if) expression. Bash Else If is kind of an extension to Bash If Else statement. In this guide, we’re going to walk through the if...else statement in bash. In this chapter of bash beginner series, you'll learn about using if-else, nested if else and case statements in bash scripts. When writing an IF statement execute statements whether the test results true or false, you use the else operator. Bonus: Bash if else statement in one line So far all the if else statement you saw were used in a proper bash script. Let’s do a few runs of the script to see how it works: You can also use case statements in bash to replace multiple if statements as they are sometimes confusing and hard to read. The code in the if block is executed when the if condition is true, otherwise the code in the else block is executed. Let’s do a few runs of the script to test it with various types of files: So far all the if else statement you saw were used in a proper bash script. #Bash Script to check whether a number is even or odd read -p "Enter a number: " number if [ $((number%2)) -eq 0 ] then echo "Number is even." For example, the following age.sh bash script takes your age as an argument and will output a meaningful message that corresponds to your age: Now do a few runs of the age.sh script to test out with different ages: Notice that I have used the -lt (less than) test condition with the $AGE variable. That's the decent way of doing it but you are not obliged to it. Test conditions varies if you are working with numbers, strings, or files. If elif else. Execution continues with the statement following the fi statement. Bash If Else : If else statement is used for conditional branching of program (script) execution in sequential programming. www.tutorialkart.com - ©Copyright-TutorialKart 2018, Example 2: Bash Else If with Multiple Conditions. Run it and see it for yourself. IF..Else Bash Statement. This tutorial describes how to compare strings in Bash. The keyword “fi” indicates the end of the inner if statement and all if statement should end with the keyword “fi”. else echo "Number is odd." If the expression evaluates to false, statements of … The condition $(whoami) = 'root' will be true only if you are logged in as the root user. The Bash elif statement enables us deciding from more choices than two; as we have seen in the above case. Also, note that the else block is optional. You can use bash if else in any section of your shell script such as for loops, while loops, functions etc. The general syntax of a basic if statement is as follows: The if statement is closed with a fi (reverse of if). 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