README.en.md

42 Barcelona - Mas O Menos

In this tutorial, you'll learn step by step how to do a little game in Shell Script

Level 0: Hello 42 !

Open a Shell

• Open a terminal on your computer

Linux

This step is for Linux users only

• Press Ctrl + Alt + T

MacOS

This step is for MacOS users only

• Press Command + Space, then type term and click on the app you want to launch

You should end up with something like this:

Create & Edit a file

In the terminal, we are using this syntax:

command --options arguments

• Let's use the command nano, which is a basic text editor
• We will give as arguments the name of the file we want to create mas_o_menos.sh
• The full command line will look like that: nano mas_o_menos.sh
• Press enter to execute it

Use Nano

• Your file should contain this line, type it:

echo 'Hello 42 !'

• Press Ctrl + x to save your file
• Press y to confirm
• Press Enter to exit

Run your program

It's time to see what you did

• Run your program with the command bash mas_o_menos.sh

Well done, you did your first Hello World !

Level 1: Let's play !

Choose an interpreter

• Indicate the interpretor to use to execute your script, the first line should be exactly: #!/usr/bin/env bash

Your file should look like that:

#!/usr/bin/env bash

echo 'Hello 42 !'

It's not a file, it's a program

• Tell the computer to treat your file as a program by giving execution permission
• Run chmod +x mas_o_menos.sh

Your file is now executable, you can run it typing: ./mas_o_menos.sh

Varaiable

You will modify your file, in order to print in the terminal the content of the variable MESSAGE, you will be able to change the message printed by changing the value of the variable

• In your file, replace 'Hello 42 !' by $MESSAGE
• Add a line just above to set the value of the variable MESSAGE: MESSAGE='Hello 42 !'
• Your file to match the following:

#!/usr/bin/env bash

MESSAGE='Hello 42 !'
echo $MESSAGE

• Save & test your program by running ./mas_o_menos.sh

Talk to me

You will make your program able to ask something to the user and get an answer

• Add a line at the bottom of the file: read ANSWER
• And another one to display the answer: echo $ANSWER
• Your file should look like that:

#!/usr/bin/env bash

MESSAGE='Hello 42 !'
echo $MESSAGE
read ANSWER
echo $ANSWER

• Save & run your program to test it !

You shall not pass

You will learn how to make your program smart

• Update the MESSAGE value to ask the age of the user: echo 'Hello 42 ! What's the answer ?'
• Add thoses lines at the bottom of the file to check if the age is equal to 42

Be careful about special characters like spaces and the quotes

if [ "$ANSWER" = 42 ]
then
	echo 'Welcome at 42 !'
else
	echo 'You shall not pass !'
fi

• Save & test, you can also remove the line: echo $ANSWER

Your file should look like this:

#!/usr/bin/env bash

MESSAGE='Hello 42 ! What's the answer ?'

echo $MESSAGE
read ANSWER

if [ "$ANSWER" = 42 ]
then
   echo 'Welcome at 42 !'
else
   echo 'You shall not pass !'
fi

Again

You will learn how to do a loop to not write two times the same piece of code

• Add between MESSAGE='Hello 42 ! What's the answer ?' and echo $MESSAGE the following

while true
do

• And after the line fi, add done Your file should be like that:

#!/usr/bin/env bash

MESSAGE="Hello 42 ! What's the answer ?"
while true
do
  echo $MESSAGE
  read ANSWER

  if [ "$ANSWER" = 42 ]
  then
    echo 'Welcome at 42 !'
  else
    echo 'You shall not pass !'
  fi
done

• Run your program to test it, press Ctrl & C to quit

The end

Add an exit to your program

• Between the line echo 'Welcome at 42 !' and the line else add exit 0

Mas O Menos

You will implement the game plus or minus, the goal is to find a hidden number in the less tries possible

• Under MESSAGE=, add SECRET=$(date +%s | rev | cut -c1-2)

This magic command line $(date +%s | rev | cut -c1-2) will generate an arbitrary number between 00 and 99 (both included), don't try to understand it

• In the line: if [ "$ANSWER" = 42 ]
  • Replace 42 by "$SECRET"
  • It should be like if [ "$ANSWER" = "$SECRET" ]
• Replace the line MESSAGE=... by MESSAGE="Hello at 42 ! What's the answer ?"
• You will add a clue:
  • Add a line to check if it's greater or lower than the secret number
  • Under echo 'You shall not pass !', add the following:

if [ "$SECRET" -gt "$ANSWER" ]
then
	echo "The secret number is greater !"
else
	echo "The secret number is lower !"
fi

• You can save and try to play

You can play with a friend, tour per tour the frst one to guess it wins Your file should be like:

#!/usr/bin/env bash

MESSAGE="Hello at 42 ! What's the answer ?"
SECRET=$(date +%s | rev | cut -c1-2)
while true
do
  echo $MESSAGE
  read ANSWER

  if [ "$ANSWER" = "$SECRET" ]
  then
    echo 'Welcome at 42 !'
	exit 0
  else
    echo 'You shall not pass !'
	if [ "$SECRET" -gt "$ANSWER" ]
then
	echo "The secret number is greater !"
else
	echo "The secret number is lower !"
fi
  fi
done

Counter

You will count how many try you do

• Initialize the counter to 0 Before while:
• Add COUNT=0 After read:
• Add COUNT="$(($COUNT + 1))" Just before exit 0
• Add echo "Score: - $COUNT"

Your file should look like that

#!/usr/bin/env bash

MESSAGE="Hello at 42 ! What's the password ?"
SECRET=$(date +%s | rev | cut -c1-2)
COUNT=0
while true
do
  echo $MESSAGE
  read ANSWER
  COUNT="$(($COUNT + 1))"

  if [ "$ANSWER" = "$SECRET" ]
  then
    echo 'Welcome at 42 !'
	echo "Score:    - $COUNT"
	exit 0
  else
    echo 'You shall not pass !'
	if [ "$SECRET" -gt "$ANSWER" ]
then
	echo "The secret number is greater !"
else
	echo "The secret number is lower !"
fi
  fi
done