BASH TUTORIAL #4: IF STATEMENTS

If statements are a low level form of conditional statements like case and or while which add on to either really well and allow the user or programmer to set up a project which can take user input and or true/false statements and provide a service until something is no longer valid or until all options have been established. If statements are a simple way to decide between two options and automatically pick the best option for the end-user. This makes coding much easier and takes fewer lines than case statements. For loops often utilise these statements as well. If statements are closer to the fourth or fifth thing you will have to practice with in a programming class and they are super easy to learn and understand. If statements are renown because they can be used in almost every language in some form or another. An example of an if statement that tests a true/false scenario would be:

if [[ $? -eq 0 ]];

then

do something

else

do something else

fi

As you can see, the if statement begins in if and ends in fi. Case statements begin in case and end in esac, however, case statements are a bit more complex to set up and learn though so these will be covered at a later time. If statements can become pretty complex in their own right. Just look at this example:

echo “Enter your favorite color”

read color

if [[ $color == blue ]];

then

echo “Your favorite color is blue”

elif [[ $color == Red ]];

then

echo “What, are you a vampire?”

elif [[ $color == Yellow ]];

then

echo “That color looks like pee”

else

echo “You have entered an unknown color, please try again”

fi

This example demonstrates acceptance of user input as well as testing different input until a strong conclusion has been reached or someone got something wrong. Kind of like a programmable rock paper scissors game, if statements can be easy but oh so beneficial. These are just a couple of the many ways that if statements can be useful. In the next tutorial I’m going to go over While loops.