show all IPs that accessed your nginx server
$ sort -g /var/log/nginx/access.log | awk '(print $1)' | uniq

convert UNIX epoch to human readable date
$ date -d @1539217802

find top 10 wordpress login abuser
$ grep "POST /.*wp-login.php" logs/*access_log | awk '{print $1}' | sort | uniq -c | sort .nr | head -10 > wp-login-top-10-abusers.txt

change timestamp of a file so thtat it matches that of a reference file
$ touch -r my_file.jpg /path/to/reference_file.jpg

compress large log to other filesystem, then delete & move the old log back
$ gzip -v9 -c /var/log/maillog > /root/maillog.gz

convert image to color #asciiart
$ jb2a -b -colors -fill climagic.org/images/clash.jpg