DAY 1

WRITING CONDITIONAL STATEMENTS IN SHELL SCRIPTING

INTRODUCTION
When writing a code, there are decisions that needs to be made base on some certain conditions. These conditions are expressions that evaluates to a boolean expression which could either be True or False.

WHAT IS A CONDITIONAL STATEMENT?
A conditional statement is a statement that helps to execute some certain code branches based on some certain conditions.

Conditional statements can be written using;
1. if
2. else
3. elif (else if)

<strong>if</strong>
Using an if statement only: if...then...fi
When you are using a single if statement, the syntax is as follows:

if [ condition ];
then
statement
fi

Note that the spaces are part of the syntax and should not be removed.

<strong>else</strong>
Using an if with an else statement: if...then...else...fi statements

When you are using an if statement and you want to add another condition, the syntax is as follows:

if [ condition ]
then
statement
else
do this by default
fi

<strong>elif (else if)</strong>
Using multiple else statements with if: if..elif..else..fi

Think of a scenario where we want to add further conditions and comparisons to make the code dynamic. In this case, the syntax would look like this:

if [ condition ]
then
statement
elif [ condition ]
then
statement
else
do this by default
fi

To create meaningful comparisons, we can use AND -a && and OR -o || as well.

For example, lets apply the if, else and elif in a grading system.

where;
Score 70 - 100 Grade A
Score 60 - 69 Grade B
Score 50 - 59 Grade C
Score 40 - 49 Graade D
Score 30 - 39 Grade E
Score 0 - 29 Grade F


Result


SOME BASIC TERMINOLOGIES TO KNOW WHEN WRITING CONDITIONAL STATEMENTS IN SHELL SCRIPTING

<strong>=</strong> is an assignment operator use to assign a value to a variable
<strong>==</strong> is called equality operator which is use to check two things that are equal
<strong>> OR -gt</strong> greater than
<strong>< OR -lt</strong> less than
<strong>>=, -ge</strong> greater than or equals to
<strong><= OR -le</strong> less than or equals to
<strong>!</strong> not, negation operator, inverse, opposite
<strong>!=</strong> not equals to, inequality operator
<strong>|| OR -O</strong> symbol for OR, logical Add
<strong>&& OR -a</strong> symbol for AND, logical multiplication

DAY 2

LOOPS IN BASH SCRIPTING

Loops allow us to take a series of commands and keep re-running them until a particular situation is reached. They are useful for automating repetitive tasks.

Loops are programs that execute continously until a certain condition is certified or met.

They are categorised into three (3)
1. while loop
2. for loop
3. until loops

<strong>while loop</strong>
The while loop is one of the easiest loop to work with. Here, while an expression is true, the lines of code keeps executing.

SYNTAX

while [ <condition> ]
do
<block of code>
done

While loop can also be executed by declaring a boolean variable
For example;

SHOULD_EXECUTE=true

while $SHOULD_EXECUTE;
do
SHOULD_EXECUTE=false
done

Lets take some examples by printing numbers from 1 to 10 using while


Result


Lets now try to print numbers from 10 down to 1


Result


Lets try using while loop by declaring a boolean variable


Result


DAY 3

Was all about Task! Task!! Task!!!

We tried to print Odd and Even numbers and also print the sum of Odd an Even numbers.


RESULT