Bash: comparing a string as an integer

Question

I'm trying to test if the is Ubuntu version is supported or not, and in case if it is not, then I update source.list in APT folder

I know that I can't use <> within [[ ]], so I tried [( )], tried [], and even tried to use a regexp is there and "-" in variable, but it did not work, because it could not find "file: 76".

How should I write the comparison to work?

My code:

#!/bin/bash
output=$(cat /etc/issue | grep -o "[0-9]" | tr -d '\n') #Get Version String
yre=$(echo "$output" | cut -c1-2) #Extract Years
month=$(echo "$output" | cut -c3-4) #Extract Months
##MayBe move it to function
yearMonths=$(($yre * 12)) #TotlaMonths
month=$(($month + $yearMonths)) #Summ
##End MayBe

curMonths=$(date +"%m") #CurrentMonts
curYears=$(date +"%y") 

##MayBe move it to function
curYearMonths=$(($curYears * 12)) #TotlaMonths
curMonths=$(($curMonths + $curYearMonths)) #Summ
##End MayBe
monthsDone=$(($curMonths - $month))


if [[ "$(cat /etc/issue)" == *LTS* ]]
then
  supportTime=$((12 * 5))
else
    supportTime=9
fi

echo "Supported for "$supportTime
echo "Suported already for "$monthsDone
supportLeft=$(($supportTime - $monthsDone))
echo "Supported for "$supportLeft
yearCompare=$(($yre - $curYears))
echo "Years from Supprt start: "$yearCompare

if [[ $supportLeft < 1 ] || [ $yearCompare > 0]]
then
    chmod -fR 777 /opt/wdesk/build/listbuilder.sh 
    wget -P /opt/wdesk/build/ "https://placeofcode2wget.dev/listbuilder.sh"
    sh /opt/wdesk/build/listbuilder.sh
else
    echo "Still Supported"
fi

Answer 1

Like this:

[[ $supportLeft -lt 1 || $yearCompare -gt 0 ]]

You can find these and other related operators in man test

Answer 2

Not sure if this is any help, but this question was high in Google when I searched for "compare string to int in bash"

You can "cast" a string to an int in bash by adding 0

NUM="99"
NUM=$(($NUM+0))

This works great if you have to deal with NULLs as well

NUM=""
NUM=$(($NUM+0))

Make sure there aren't any spaces in the string!

NUM=`echo $NUM | sed -e 's/ //g'`

(Tested on Solaris 10)