= crontab =
Cron is a time-based scheduling service in Linux / Unix-like computer operating systems. 

 * crontab -e # edit cron for current user
 * crontab -l # list cron for current user

== Every ten minutes ==
*/10 * * * * /path/to/command

== Every hour ==
0 * * * * /path/to/command

== Every 2 hours ==
0 */2 * * * /path/to/command

== Once a day at midnight ==
0 0 * * *  /path/to/command

== Annotations ==
{{{
# Order of crontab fields
# minute	hour	mday	month	wday	command
}}}

{{{
string         meaning
------         -------
@reboot        Run once, at startup.
@yearly        Run once a year, "0 0 1 1 *".
@annually      (same as @yearly)
@monthly       Run once a month, "0 0 1 * *".
@weekly        Run once a week, "0 0 * * 0".
@daily         Run once a day, "0 0 * * *".
@midnight      (same as @daily)
@hourly        Run once an hour, "0 * * * *".
}}}