For all the Linux admins out there – Add this to the header of all your crontabs.
… and it becomes a lot clearer to anyone reading them…
# * * * * * command_to_be_executed
# - - - - -
# | | | | |
# | | | | +----- day of the week (0 - 6) (Sunday=0)
# | | | +--------- month (1 - 12)
# | | +------------- day of the month (1 - 31)
# | +----------------- hour (0 - 23)
# +--------------------- min (0 - 59)
#
# Asterisk (*) any value
# Comma (,) value list separator (0,20,30,45)
# Dash (-) range of values (8-17)
# Slash (/) steps values (*/20)
#
# @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 * * *"
# @hourly Run once an hour, "0 * * * *"
Njoy!