#!/bin/bash
LOGS=( $(sudo find /var/tmp/portage/ -mindepth 1 -maxdepth 5 -name "build.log") )
LEN=${#LOGS[@]}

for (( i=0; i<$LEN; i++ ));
do
    echo "$(( $i + 1 )) - ${LOGS[$i]}"
done

echo
read -p 'Select number to show logs: ' NUMBER

sudo tail -f ${LOGS[$NUMBER-1]}