When you’re writing a bash script, you may only want something to happen if multiple conditions are met, or if one of multiple conditions are met. When comparing strings in Bash you can use the following operators: string1 = string2 and string1 == string2 - The equality operator returns true if the operands are equal. The fi (if backward) keyword marks the end of the if block. You can use bash if else in any section of your shell script such as for loops, while loops, functions etc. ... else echo "none of the above" fi. Example 1: Simple if statement at the command line, 3. You can have only one else clause in the statement. The “if then elif then else fi” example mentioned in above can be converted to the nested if as shown below. Using else if statement in bash You can use an elif (else-if) statement whenever you want to test more than one expression (condition) at the same time. The Bash elif statement enables us deciding from more choices than two; as we have seen in the above case. If the first test command evaluates to true, it executes the first action you want to happen. In the if/then/elif/else form of the if statement, the first else becomes another if statement or “elif” instead of a simple else. Multiple conditions in an expression are joined together using bash logical operators. The syntax of the if..else statement is : if EXPRESSION then STATEMENTS1 else STATEMENTS2 fi STATEMENT1 will be executed only if the expression is true. According to the expressions, statement 2 should be echoed to the console. In case one if the condition goes false then check another if conditions. Bash allows you to nest if statements within if statements. In this section of our Bash Scripting Tutorial you will learn the ways you may use if statements in your Bash scripts to help automate tasks. And toady you have learned a thing or two about the if else condition in bash programming. Using an else statement, we can write a two-part conditional. When working with Bash and shell scripting, you might need to use conditions in your script.. Bash if Statement. It's a cheat way, but it's effective. The first line of the script is simply making sure that we will be using the Bash interpreter for our script. Enjoy if statements in Bash, and leave us some thoughts with your best if tips and tricks! Conditional statements, in other words, define ‘if a condition is true or false, then do this or that, and if the opposite is true, do something else’. Android Programming Tutorials. The keyword “fi” indicates the end of the inner if statement and all if statement should end with the keyword “fi”. Otherwise, the commands following the else keyword are executed. The following script will prompt you to enter three numbers and will print the largest number among the three numbers. We also have the special elif on which we will see more in a minute. If statement and else statement could be nested in bash. In certain scenarios, you will require doing something; for example showing a message box to the user or action failure, display a message or perform some default action if the condition is false. The code in the if block is executed when the if condition is true, otherwise the code in the else block is executed. 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 Else is kind of an extension to Bash If statement. IF..Else Bash Statement When writing an IF statement execute statements whether the test results true or false, you use the else operator. The semi-colon (;) after the conditional expression is must. Alan Alan. LinuxConfig is looking for a technical writer(s) geared towards GNU/Linux and FLOSS technologies. Example 2: Using and if statement from within a Bash shell script, How To Use Bash Subshells Inside If Statements, How to Use Bash Subshells Inside if Statements, Useful Bash Command Line Tips and Tricks Examples - Part 6, Any utility which is not included in the Bash shell by default can be installed using. If the result of TEST-COMMAND to True, it will execute the STATEMENTS1. If the expression evaluates to true, statements of if block are executed. Android Programming Tutorials. First, the condition inside the brackets is evaluated. The shell can accommodate this with the if/then/else syntax. If Else statement along with commands in if and else blocks could be written in a single line. Consider the following test.sh: Here we stepped through the first if statement, and since 0 does not match 1, the else clause is activated. Bash if statement, if else statement, if elif else statement and nested if statement used to execute code based on a certain condition. TECHENUM. Code language: Bash (bash) In the code of block above if the str1 and str2 are both same the then block is executed or else the else block is executed. This tutorial describes how to compare strings in Bash. For example, input the marks of student and check if marks are greater or equal to 80 then print “Very Good”. In Bash elif, there can be several elif blocks with a boolean expression for each one of them. Conditional statements, in other words, define ‘if a condition is true or false, then do this or that, and if the opposite is true, do something else’.This is the most basic function of any conditional statement. It is good practice to always set this for Bash and other scripts (for other scripts, you will want to set this to whatever interpreter which is going to execute your script, for example #!/usr/bin/python3 for a Python 3 (.py3 for example) scripts etc). The shell first evaluates condition 1, then condition 2, and so on, stopping with the first condition that succeeds. Simple guide to concatenate strings in bash with examples; Beginners guide to use getopts in bash scripts & examples; Difference .bashrc vs .bash_profile (which one to use?) 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. 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The echo statement prints its argument, in this case, the value of the variable count , to the terminal window. Follow answered Jan 20 '17 at 23:51. else other-commands fi. You saw in the above example, no action is performed or any statement displayed when the condition was false. Whereas in the second if-else expression, condition is false and hence the statements in the else block are executed. Following is an example for the same. As we trying to query whether 1 is not equal (-ne) to 1 this time, and as 1 does equal 1 (wich is not the case), the condition formulated in this if statement is false, and we run into our else statement with the matching text printed. An expression is associated with the if statement. When working with Bash and shell scripting, you might need to use conditions in your script.. End the statements in if and else blocks with a semi-colon (;). Comparison Operators # Comparison operators are operators that compare values and return true or false. In this article, we explored examples exemplifying the if, elif, else, then and fi clauses in Bash. If the expression evaluates to false, statements of else block are executed. If you are just starting to explore the Bash coding language, you will soon find yourself wanting to create conditional statements. And, for a somewhat more advanced look at what if can do for you when combined with subshells, checkout our How To Use Bash Subshells Inside If Statements article! Let’s change this slightly: Here we introduced an else clause; what commands to execute when the condition in the if statement has proven to be false (or not true). Set of commands to be run when the is false. If the expression evaluates to false, statements of else … What extension is given to a Bash Script File? Bash if Statements: if, elif, else, then, fi. elif (else if) is used for multiple if conditions. if TEST-COMMAND then STATEMENTS else STATEMENTS fi By using the else operator, your if statement will execute a different set of statements depending on your test case. Syntax and usage of if-else statement with example Bash Scripts are provided in this tutorial. It is good to note that you can easily copy and paste any if statement shown here or elsewhere, and use it inside a Bash shell script. If our condition is met, a block of code will be run; otherwise, another block of code will be run. Bash if elif Statement. The script did exactly the same, but in a much more flexible and shorter way, requiring only one level of if statement depth and with cleaner overall code. Two types of conditional statements can be used in bash. These are, ‘If' and ‘case' statements. In Bash else-if, there can be multiple elif blocks with a boolean expression for each of them. For example, if a user enters the marks 90 or more, we want to display “Excellent”. For example, find out if file exists (true condition) or not (false condition) and take action based on a condition result. If you are just starting to explore the Bash coding language, you will soon find yourself wanting to create conditional statements. If statements (and, closely related, case statements) allow us to make decisions in our Bash scripts.