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|
.TH CRON 8
.CT 1 sa_auto
.SH NAME
cron \- clock daemon
.SH SYNOPSIS
.B /etc/cron
.SH DESCRIPTION
.I Cron
executes commands at specified dates and times
according to the instructions in the file
.FR /etc/crontab .
It should be run once from
.IR rc (8).
.PP
.I Crontab
entries are lines of seven fields separated by blanks or tabs:
.IP
.I
login minute hour day month weekday command
.PP
.I Login
is the login name under
whose userid and groupid
the command should be executed.
The next five fields are integer patterns for
.PD0
.RS
.TP \w'day\ of\ month\ \ 'u
minute
0-59
.TP
hour
0-23
.TP
day of month
1-31
.TP
month of year
1-12
.TP
day of week
0-6; 0=Sunday
.PD
.RE
.PP
Each pattern may
contain a number in the range above;
two numbers separated by
a hyphen
meaning an inclusive range;
a list of numbers separated by
commas meaning any of the numbers;
or an asterisk meaning all legal values.
.PP
The last field is a string
to be executed by the shell,
after replacing
.L %
with newline.
.PP
It is wise to spread the times of activities to avoid
bogging the system down at favorite hours.
.PP
.I Cron
examines
.I crontab
every minute.
.SH EXAMPLES
.EX
daemon 17 3 * * * /usr/bin/calendar - # reminders at 0317
adm 15 4 1,15 * * ac -p | mail adm # bimonthly accounts
root 0 12 22-28 11 4 /etc/wall Time for Thanksgiving dinner
.EE
.SH FILES
.F /etc/crontab
.SH SEE ALSO
.IR at (1)
.SH BUGS
The behavior of
.L %
in
.I crontab
entries is nonstandard.
Strings following
.L %
should be delivered to the command as standard input.
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