bash if else

Bash Script 'if-else' Statements - Conditional Statements are those which help us take certain decisive actions against certain different conditions. If the expression evaluates to true, statements of if block are executed. Your articles will feature various GNU/Linux configuration tutorials and FLOSS technologies used in combination with GNU/Linux operating system. 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. Condition making statement is one of the most fundamental concepts of any computer programming. An expression is associated with the if statement. These are, ‘If' and ‘case' statements. In case one if the condition goes false then check another if conditions. In this article, we explored examples exemplifying the if, elif, else, then and fi clauses in Bash. First, the condition inside the brackets is evaluated. In this statement, we are comparing one to one. Next we add our if statement again by using echo and a double redirector >> which unlike > will not create a new file, and simply append text to the file indicated. In bash, you can use if statements to make decisions in your code. In this guide, we’re going to walk through the if...else statement in bash. 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. else other-commands fi. The Bash elif statement enables us deciding from more choices than two; as we have seen in the above case. elif (else if) is used for multiple if conditions. 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. The elif clause provides us with extra shorthand flexibility short-cutting the need nested statements. In if-else statements, the execution of a block of statement is decided based on the result of the if condition. 1.1 if/then/else Example. The keyword “fi” indicates the end of the inner if statement and all if statement should end with the keyword “fi”. When you use > a new file will be created, and any file with the same name will be overwritten so please use it with care. Follow answered Jan 20 '17 at 23:51. If statements (and, closely related, case statements) allow us to make decisions in our Bash scripts. For example: Here we simply created a small myscript.sh shell script by using echo and the > redirector to redirect the output from our echo to a file. For example, if a user enters the marks 90 or more, we want to display “Excellent”. Bash If..Else Statement. Syntax of If Else statement in Bash Shell Scripting is as given below : Observe that if, then, else and fi are keywords. It is just like an addition to Bash if-else statement. We also looked at moving such statements into Bash scripts. Following is the form of Bash if..else statement: if TEST-COMMAND then STATEMENTS1 else STATEMENTS2 fi. These statements are also used in bash to perform automated tasks like another programming language, just the syntax is a little bit different in bash. IF..Else Bash Statement When writing an IF statement execute statements whether the test results true or false, you use the else operator. 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’. If not, STATEMENT2 will be executed instead. Try changing the code and try executing it. If our condition is met, a block of code will be run; otherwise, another block of code will be run. In this Bash Tutorial, we have learnt about the syntax and usage of bash if else statement with example bash scripts. 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. Android Programming Tutorials. 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. In this example, we shall look into a scenario where if expression has multiple conditions. Syntax and usage of if-else statement with example Bash Scripts are provided in this tutorial. Bash If Else : If else statement is used for conditional branching of program (script) execution in sequential programming. Below is how the bash elif looks like: if [ [ test-command1 ] ] then echo elif [ [ test-command2 ] ] then echo else echo fi. In this example, we shall look into two scenarios where in first if-else statement, expression evaluates to true and in the second if-else statement, expression evaluates to false. For example, find out if file exists (true condition) or not (false condition) and take action based on a condition result. if, if-else and else-if statements could be nested in each other. 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. If else is a conditional statement used in Bash scripting to execute different parts of your script based on the result of the if condition. The base for the 'if' constructions in bash is this: if [expression]; then code if 'expression' is true. If value equals 1. 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). This is the most basic function of any conditional statement. if elif and else statements are useful where we have more than two programs for execution, and need to execute only one based on results of if and elif condition. Bash if elif Statement. If the expression evaluates to true, statements of if block are executed. 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When we execute the script we can see that the output is being generated as expected (1 matches 1): Matched!. The “if then elif then else fi” example mentioned in above can be converted to the nested if as shown below. 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! Bash If-Else Statement Syntax The syntax of the if-else statement in bash is: if [condition] then //if block code else // else block code fi If the condition evaluates to true, the if block code is executed, and if the condition evaluates to false then the else block code is executed. 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. if [ $value -eq 1 ] then … The following types of conditional statements can be used in bash. 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