#!/bin/bash
for i in log1.txt log2.txt
do <$i awk '/^[[:digit:]]/ { close("base64 -w0"); printf("\n%s\t",$1); } { print | "base64 -w0" }' | tail -n+2 > ${i%.*}.b64
done
sort -nr log?.b64 | uniq | cut -f2 |  base64 -d > full_log.txt