Question

I have a shell that runs where the preset env variables include:

FOOCOUNT=4
FOO_0=John
FOO_1=Barry
FOO_2=Lenny
FOO_3=Samuel

I can not change the way I get this data.

I want to run a loop that generates up the variable and uses the contents.

echo "Hello $FOO_count"

This syntax is however wrong and that is what I am searching for…

count=$FOOCOUNT
counter=0
while [ $counter -lt $count ]
do
#I am looking for the syntax for: <<myContructedVar= $ + 'FOO_' + $counter>>
counter=`expr $counter + 1`
echo "Greeting #$counter: Hello, ${myContructedVar}."
done

Thanks very much

Answer 1

The key is eval:

count=$FOOCOUNT
counter=0
while [ $counter -lt $count ]
do
    myConstructedVar=FOO_$counter
    counter=`expr $counter + 1`
    echo "Greeting #$counter: Hello, `eval echo \$${myConstructedVar}`."
done

The loop arithmetic is old school – the way I write the code. Modern shells have more arithmetic built in – but the question is tagged Bourne shell.