$ tail -f /var/log/auth.log
Mar 4 08:39:01 c521 CRON[27505]: pam_unix(cron:session): session opened for user root by (uid=0)
Mar 4 08:39:01 c521 CRON[27505]: pam_unix(cron:session): session closed for user root
Mar 4 09:09:01 c521 CRON[27565]: pam_unix(cron:session): session opened for user root by (uid=0)
Mar 4 09:09:02 c521 CRON[27565]: pam_unix(cron:session): session closed for user root
Mar 4 09:17:01 c521 CRON[27595]: pam_unix(cron:session): session opened for user root by (uid=0)
Mar 4 09:17:01 c521 CRON[27595]: pam_unix(cron:session): session closed for user root
Mar 4 09:39:01 c521 CRON[27673]: pam_unix(cron:session): session opened for user root by (uid=0)
Mar 4 09:39:01 c521 CRON[27673]: pam_unix(cron:session): session closed for user root
Mar 4 10:09:01 c521 CRON[27984]: pam_unix(cron:session): session opened for user root by (uid=0)
Mar 4 10:09:02 c521 CRON[27984]: pam_unix(cron:session): session closed for user root