Using variables

Arithmetic evaluation

echo 1 + 1

echo $((1+1))

echo $[1+1]

echo $[3/4]

echo $[3/4] | bc -l

Using exitcodes

cd /noexisting > /dev/null
echo $?
echo $?

Capturing output

TODAY=$(date +%Y-%m-%d)
echo $TODAY

TODAY=`date +%Y-%m-%d`
echo $TODAY

Reading user input

read -p "Enter your name: " name
echo "Hello $name"