Output file lines from last to first in Bash

Question

I want to display the last 10 lines of my log file, starting with the last line- like a normal log reader. I thought this would be a variation of the tail command,

Answer 1

You can do that with pure bash:

#!/bin/bash
readarray file
lines=$(( ${#file[@]} - 1 ))
for (( line=$lines, i=${1:-$lines}; (( line >= 0 && i > 0 )); line--, i-- )); do
    echo -ne "${file[$line]}"
done

./tailtac 10 < somefile

./tailtac -10 < somefile

./tailtac 100000 < somefile

./tailtac < somefile