How to use the Bash “if” Statement?

In order to execute a Bash “if else” statement, you have to use four different keywords : if, then, else and fi :

1. if : represents the condition that you want to check;
2. then : if the previous condition is true, then execute a specific command;
3. else : if the previous condition is false, then execute another command;

1. How do you write an if statement in shell script?
2. How do you use if in a script?
3. How do I write an if statement in Linux?
4. How do you write an OR statement in bash?
5. What is $? In Bash?
6. How do you set a variable in Shell?
7. What is if else statement with example?
8. What is if in shell script?
9. What is if else if else statement?
10. What is in if statement in Linux?
11. What is in if statement bash?
12. How do I get input in bash?

How do you write an if statement in shell script?

Their description with syntax is as follows:

1. if statement. This block will process if specified condition is true. ...
2. if-else statement. ...
3. if..elif..else..fi statement (Else If ladder) ...
4. if..then..else..if..then..fi..fi..(Nested if) ...
5. Syntax: case in Pattern 1) Statement 1;; Pattern n) Statement n;; esac. ...
6. Example 2:

How do you use if in a script?

Conditional Statements

1. Use if to specify a block of code to be executed, if a specified condition is true.
2. Use else to specify a block of code to be executed, if the same condition is false.
3. Use else if to specify a new condition to test, if the first condition is false.

How do I write an if statement in Linux?

The basic structure of the if statement looks like this:

1. if [ conditional-expression ] then. commands. else. other-commands. ...
2. #!/bin/bash. echo “How old are you?” read age. if [ “$age” -ge 21 ] ; then. ...
3. #!/bin/bash. echo “How old are you?” read age. if [ “$age” -le 21 ] ; then. ...
4. #! /bin/bash. file=test_file. if [ -e $file ] then.

How do you write an OR statement in bash?

1. In bash, 'or' operator is '||' (C style). – ...
2. You can also use -o within the same [ ] . – ...
3. @Thor I'd prefer || and separate [ ] over -o for portability simply because [ is not guaranteed to support more than 4 arguments. ...
4. @jw013 Thanks.

What is $? In Bash?

$? is a special variable in bash that always holds the return/exit code of the last executed command. You can view it in a terminal by running echo $? . Return codes are in the range [0; 255]. A return code of 0 usually means everything is ok.

How do you set a variable in Shell?

Unix / Linux - Using Shell Variables

1. Defining Variables. Variables are defined as follows − variable_name=variable_value. ...
2. Accessing Values. To access the value stored in a variable, prefix its name with the dollar sign ($) − ...
3. Read-only Variables. Shell provides a way to mark variables as read-only by using the read-only command. ...
4. Unsetting Variables.

What is if else statement with example?

Example 2: if...else statement

Enter an integer: 7 7 is an odd integer. When the user enters 7, the test expression number%2==0 is evaluated to false. Hence, the statement inside the body of else is executed.

What is if in shell script?

Conditions in Shell Scripts

An if-else statement allows you to execute iterative conditional statements in your code. We use if-else in shell scripts when we wish to evaluate a condition, then decide to execute one set between two or more sets of statements using the result.

What is if else if else statement?

if statement - executes some code if one condition is true. if...else statement - executes some code if a condition is true and another code if that condition is false.

What is in if statement in Linux?

if is a command in Linux which is used to execute commands based on conditions. The 'if COMMANDS' list is executed. ... Otherwise, the 'else COMMANDS' list is executed, if present. The exit status of the entire construct is the exit status of the last command executed, or zero if no condition tested true.

What is in if statement bash?

The if in a Bash script is a shell keyword that is used to test conditions based on the exit status of a test command. An exit status of zero, and only zero, is a success, i.e. a condition that is true. ... Tests commands in the bash if statement, and bash elif clauses, are executed in order until one test succeed.

How do I get input in bash?

Example 1:

1. #!/bin/bash.
2. # Read the user input.
3. echo "Enter the user name: "
4. read first_name.
5. echo "The Current User Name is $first_name"
6. echo.
7. echo "Enter other users'names: "
8. read name1 name2 name3.