Compare Decimals in Bash while Loop

Question

In the below code, ShellCheck throws an error in the while clause.

count=10.0
while [ $count -le 20.0 ]
do
    echo "Hello"
    count=$(bc<<< "scale=4; (count+0.1)")
done

ShellCheck says:

Decimals not supported, either use integers or bc

I am not quite sure how to use bc in a while loop.

while [ $(bc <<< "scale=4; (count -le 20.0)" ]

How do I compare decimal numbers in a while clause? Any advice?

Answer 1

Bash doesn't support floating point arithmetic. You can either use bc:

count="10.0"
limit="12.0"
increment="0.1"

while [ "$(bc <<< "$count < $limit")" == "1"  ]; do
    echo "Hello"
    count=$(bc <<< "$count+$increment")
done

or awk:

while awk 'BEGIN { if ('$count'>='$limit') {exit 1}}'; do
    echo "Hello"
    count=$(bc <<< "$count+$increment")
done

I just wonder: why not (directly) count from 10.0 to 12.0 ?

for i in $(seq 10.0 0.1 12.0); do
    echo "Hello"
done