'\"macro stdmacro
.if n .pH g1a.cron @(#)cron	40.11 of 1/17/90
.\" Copyright 1989 AT&T
.nr X
.if \nX=0 .ds x} cron 1M "Essential Utilities" "\&"
.if \nX=1 .ds x} cron 1M "Essential Utilities"
.if \nX=2 .ds x} cron 1M "" "\&"
.if \nX=3 .ds x} cron "" "" "\&"
.TH \*(x}
.SH NAME
\f4cron\f1 \- clock daemon
.SH SYNOPSIS
\f4/usr/sbin/cron\f1
.SH DESCRIPTION
The \f4cron\fP command starts a process that
executes commands at specified dates and times.
Regularly scheduled commands can be specified according
to instructions found in \f4crontab\fP files in the directory
\f4/var/spool/cron/crontabs\f1.
Users can submit their own \f4crontab\fP file via the \f4crontab\fP command.
Commands which are to be executed only once may be
submitted via the \f4at\fP command.
.PP
\f4cron\fP only examines \f4crontab\fP files and \f4at\fP
command files during process initialization and when a file changes via
the \f4crontab\fP or \f4at\fP commands.
This reduces the overhead of checking for new or
changed files at regularly scheduled intervals.
.PP
Since \f4cron\fP never exits, it should be executed only once.
This is done routinely
through \f4/sbin/rc2.d/S75cron\f1 at system boot time.
\f4/usr/sbin/cron.d/FIFO\f1 is used as a lock file to prevent
the execution of more than one 
\f4cron\fP.
.PP
To keep a log of all actions taken by \f4cron\fP, 
.SM CRONLOG=YES
(by default) must be specified
in the \f4/etc/default/cron\fP file.
If
.SM CRONLOG=NO
is specified,
no logging is done.
Keeping the log is a user configurable
option since \f4cron\fP usually creates huge log files.
.SH FILES
.TP 1.75i
\f4/usr/sbin/cron.d\fP
main cron directory
.TP
\f4/etc/default/cron\fP
used to maintain a log
.TP
\f4/usr/sbin/cron.d/FIFO\fP
used as a lock file
.TP
\f4/usr/sbin/cron.d/log\fP
accounting information
.TP
\f4/var/spool/cron\fP
spool area
.SH "SEE ALSO"
\f4at\fP(1), \f4crontab\fP(1), \f4sh\fP(1)
in the \f2User's Reference Manual\f1.
.SH DIAGNOSTICS
A history of all actions taken by \f4cron\fP are recorded in
\f4/usr/sbin/cron.d/log.\f1
.\"	@(#)cron.1m	6.3 of 9/2/83
.Ee
