Evaluating binary numbers

Let's say we want to introduce another if condition and use elif (short for else if):

#!/bin/bash
AGE=21
if [ ${AGE} -lt 18 ]; then
 echo "You must be 18 or older to see this movie"
elif [ ${AGE} -eq 21 ]; then
 echo "You may see the movie and get popcorn"
else
 echo "You may see the movie!"
 exit 1
fi

echo "This line might not get executed"

If AGE is set and equals 21, then the snippet will echo:

You may see the movie and get popcorn
This line might not get executed

Using if, elif, and else, combined with other evaluations, we can execute specific branches of logic and functions or even exit our script. To evaluate raw binary variables, use the following operators:

• -gt (greater than >)
• -ge (greater or equal to >=)
• -lt (less than <)
• -le (less than or equal to <=)
• -eq (equal to)
• -nq (not equal to)