CRON(8)

NAME
cron - clock daemon

SYNOPSIS
/etc/cron

DESCRIPTION
Cron executes commands at specified dates and times according to the instructions in the files /usr/lib/crontab and /usr/lib/crontab.local. None, either one, or both of these files may be present. Since cron never exits, it should only be executed once. This is best done by running cron from the initialization process through the file /etc/rc; see init(8).

The crontab files consist of lines of seven fields each. The fields are separated by spaces or tabs. The first five are integer patterns to specify:

•   minute (0-59)

•   hour (0-23)

•   day of the month (1-31)

•   month of the year (1-12)

•   day of the week (1-7 with 1 = Monday; for compatibility with newer systems, Sunday may also be specified as day 0)

Each of these patterns may contain:

•   a number in the range above

•   two numbers separated by a minus meaning a range inclusive

•   a list of numbers separated by commas meaning any of the numbers

•   an asterisk meaning all legal values

The sixth field is a user name: the command will be run with that user's uid and permissions. The seventh field consists of all the text on a line following the sixth field, including spaces and tabs; this text is treated as a command which is executed by the Shell at the specified times. A percent character (``%'') in this field is translated to a new-line character.

Both crontab files are checked by cron every minute, on the minute.

FILES
/usr/lib/crontab
/usr/lib/crontab.local