I’m trying hard to write a script function that reads the last line of a log file while that file is being updated, to use it in arguments.

My idea is to stop the loop when a file is created by another function of the same script. That seems to work. However, after spending hours, I have not been able to actually get the data from the log file.

Got these two versions now;

while true; do
    if [[ -f "CheckFile" ]]; then
        break
    else
        Variable=$(tail -n 1 "${LogFile}" | grep -E "(Installing.* of .*)")
        echo "${Variable}"
    fi
done
rm -f "CheckFile"

while true; do
    if [[ -f "CheckFile" ]]; then
        break
    else
        while read line; do
            if [[ -n $line ]]; then
                echo "test $line"
            else
                continue
            fi
        done < <(tail -n 1 "${LogFile}" | grep -E "(Installing.* of .*)")
    fi
done
rm -f "CheckFile"

I expected both versions will give an updated value as long as the while loop runs. Also tried with tail -f, but that seems to never end.