Tham khảo:
[1] - http://collectd.1051573.n5.nabble.com/collectd-Notification-issues-td4595945.html
[1] - http://urbanautomaton.com/blog/2014/09/09/redirecting-bash-script-output-to-syslog/
[2] - https://serverfault.com/questions/336217/how-do-i-log-every-command-executed-by-a-user
[4] - https://www.gnu.org/software/bash/manual/bashref.html#Shell-Parameter-Expansion