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bash script to calculate age difference with loop

I essentially want to calculate this:
"calculate how much beer an 18+ user has drunk statistically (100 liters/year) and print this information for the user."

Not sure how to calculate it i.e. use a loop or other to use the difference in specified age versus user input age, multiply the result, I made an attempt in the last section of code.

Code:

#!/bin/bash

 

# This script check's the user's age and if they can legally drink alcohol



age=16



lage=18



echo "What age are you?"



read uage



years=$[$age - $uage]



beer=$[$years ge $lage]



if [ "$uage" -ge "$age" ] ; then

    echo -e "You are $uage and are of legal age to drink alcohol\n" && 

    echo -e "You have drank $ litres of beer since you turned 18 years of age."

    exit 1

else

    echo -e "You are $uage and are not of legal age to drink alcohol\n" &&

    echo -e "You have to wait $years years before you can legally drink alcohol"

fi 



while [$beer]; do

        echo " "

    let $beer = $beer+1 * 100

    done



if [ "$uage" == "$lage" ] ; then

    echo " You have drank $beer litres of beer since you were born"

else

    echo "You have not drank much beer"

fi

Code:

lage=18

read -p "What is your age? " uage

(( beeryears = age - lage  ))

(( beer = $beeryears * 100 ))

echo $beer

Quote:

Originally Posted by uhelp (Post 4687377)

Code:

lage=18

read -p "What is your age? " uage

(( beeryears = age - lage  ))

(( beer = $beeryears * 100 ))

echo $beer

It only works if the user age is 18 and not if older. I ran this code separately without adding to my own.

What is your age? 19
-1800

What is your age? 78
-1800

What is your age? 23
-1800

Code:

beerperyear=100

legalage=18



read -p "What is your age? " age



beer=$(( (age - legalage) * beerperyear ))



if (( beer > 0 )); then

    echo "You've drank $beer liters of beer."

else

    beer=0

    echo "You're not old enough to have drunk beer."

fi

For fractional years (but integral liters of beer) it's easiest to use awk:

Code:

beer=$( echo "$age $legalage $beerperyear" | awk '{ printf("%.0f\n", ($1-$2)*$3) }' )

The bash code example from uhelp has mixed up uage and age variables, a simple change will fix it:

Code:

(( beeryears = uage - lage ))