[unix-history] / usr / man / man8 / cron.8

.TH CRON 8  "4 February 1983"
.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
/usr/lib/crontab.
Since
.I cron
never exits,
it should only be executed once.
This is best done by running
.I cron
from the initialization
process through the file
/etc/rc;
see
.IR init (8).
.PP
Crontab
consists of lines of six fields each.
The fields are separated by spaces or tabs.
The first five are integer patterns to
specify the
minute (0-59),
hour (0-23),
day of the month (1-31),
month of the year (1-12),
and day of the week (1-7 with 1=Monday).
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;
or an asterisk meaning all legal values.
The sixth field is a string
that is executed by the Shell at the
specified times.
A percent character
in this field is translated to a new-line
character.
Only the first line (up to a % or end of line)
of the command field is executed by the Shell.
The other lines are made available to the
command as standard input.
.PP
Crontab is examined by
.I cron
every minute.
.SH FILES
/usr/lib/crontab
Commit	Line	Data
ce1056cb C	1	.TH CRON 8 "4 February 1983"
	2	.SH NAME
	3	cron \- clock daemon
	4	.SH SYNOPSIS
	5	.B /etc/cron
	6	.SH DESCRIPTION
	7	.I Cron
	8	executes commands at specified dates and times
	9	according to the instructions in the file
	10	/usr/lib/crontab.
	11	Since
	12	.I cron
	13	never exits,
	14	it should only be executed once.
	15	This is best done by running
	16	.I cron
	17	from the initialization
	18	process through the file
	19	/etc/rc;
	20	see
	21	.IR init (8).
	22	.PP
	23	Crontab
	24	consists of lines of six fields each.
	25	The fields are separated by spaces or tabs.
	26	The first five are integer patterns to
	27	specify the
	28	minute (0-59),
	29	hour (0-23),
	30	day of the month (1-31),
	31	month of the year (1-12),
	32	and day of the week (1-7 with 1=Monday).
	33	Each of these patterns may
	34	contain a number in the range above;
	35	two numbers separated by
	36	a minus
	37	meaning a range inclusive;
	38	a list of numbers separated by
	39	commas meaning any of the numbers;
	40	or an asterisk meaning all legal values.
	41	The sixth field is a string
	42	that is executed by the Shell at the
	43	specified times.
	44	A percent character
	45	in this field is translated to a new-line
	46	character.
	47	Only the first line (up to a % or end of line)
	48	of the command field is executed by the Shell.
	49	The other lines are made available to the
	50	command as standard input.
	51	.PP
	52	Crontab is examined by
	53	.I cron
	54	every minute.
	55	.SH FILES
	56	/usr/lib/crontab