Counting program fails in arithmetic test

Question

having a little trouble with this rather basic script. This script works on Bash in my macbook pro, but not on my Linux Mint desktop, which also uses bash.

I can't figure out what's wrong with it.

I'm still getting an error from bash saying:

line 6: [: -lt: unary operator expected
line 16: [: -gt: unary operator expected

with this updated code:

#!/bin/bash
clear
counter=0

function countup {
while [ $counter -lt 500 ]
do
  ((counter++))
  echo $counter
  sleep 0.2
done
countdown
}

function countdown {
while [ $counter -gt 0 ]
do
  ((counter--))
  echo $counter
  sleep 0.2
done
countup
}

countup

Answer 1

Try this:

#!/bin/bash
clear
counter=0

function countup {
    while [[ $counter -lt 500 ]]; do
        ((counter++))
        echo $counter
        sleep 0.2
    done

    countdown
}

function countdown {
    while [[ $counter -gt 0 ]]; do
        ((counter--))
        echo $counter
        sleep 0.2
    done

    countup
}

countup

[[ ]] is a bit more robust to unvalued variables. But, this script does run. It seems that you typed it differently here than your machine. This also looks like it will count up and down forever, but that seems to be intentional.