DevOps Day-7 Basic Linux Shell Scripting for DevOps Engineers

Welcome to Day 7 of our Basic Linux Shell Scripting for DevOps Engineers! In today's session, we will cover the following topics:

1. Loops: Loops are used to execute a set of commands repeatedly until a certain condition is met. The most commonly used loops in shell scripting are "for" loops and "while" loops.

• For loop: A for loop is used to iterate over a list of items. The syntax for a for loop is as follows:

bashCopy codefor variable_name in item1 item2 item3 ... itemN
do
    # commands to execute
done

For example, the following for loop will iterate over a list of items and print each item to the console:

bashCopy codefor item in apple banana orange
do
    echo $item
done

• While loop: A while loop is used to execute a set of commands repeatedly as long as a certain condition is true. The syntax for a while loop is as follows:

bashCopy codewhile [ condition ]
do
    # commands to execute
done

For example, the following while loop will execute the "ls" command repeatedly until the current directory does not contain any files:

bashCopy codewhile [ "$(ls)" ]
do
    ls
done

1. Conditional statements: Conditional statements are used to execute a set of commands only if a certain condition is met. The most commonly used conditional statements in shell scripting are "if" statements and "case" statements.

• If statement: An if statement is used to execute a set of commands only if a certain condition is true. The syntax for an if statement is as follows:

bashCopy codeif [ condition ]
then
    # commands to execute
fi

For example, the following if statement will execute the "echo" command only if the value of the variable "x" is greater than 10:

bashCopy codeif [ $x -gt 10 ]
then
    echo "x is greater than 10"
fi

• Case statement: A case statement is used to execute a set of commands based on the value of a variable. The syntax for a case statement is as follows:

bashCopy codecase variable_name in
    pattern1)
        # commands to execute
        ;;
    pattern2)
        # commands to execute
        ;;
    *)
        # default commands to execute
        ;;
esac

For example, the following case statement will execute a set of commands based on the value of the variable "fruit":

bashCopy codecase $fruit in
    apple)
        echo "This is an apple"
        ;;
    banana)
        echo "This is a banana"
        ;;
    *)
        echo "This is not a recognized fruit"
        ;;
esac

These are some of the advanced concepts used in shell scripting. By mastering these concepts, you will be able to write more efficient and powerful scripts. Keep practicing and experimenting with shell scripting, and you'll become a proficient DevOps engineer in no time!