cron.8

source code of crond

.\"/* Copyright 1988,1990,1993 by Paul Vixie
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.\" 
.\" $Id: cron.8,v 2.2 1993/12/28 08:34:43 vixie Exp $
.\" 
.TH CRON 8 "20 December 1993"
.UC 4
.SH NAME
cron \- daemon to execute scheduled commands (Vixie Cron)
.SH SYNOPSIS
cron
.SH DESCRIPTION
.I Cron
should be started from /etc/rc or /etc/rc.local.  It will return immediately,
so you don't need to start it with '&'.
.PP
.I Cron
searches /var/cron/tabs for crontab files which are named after accounts in
/etc/passwd; crontabs found are loaded into memory.
.I Cron
also searches for /etc/crontab which is in a different format (see
.IR crontab(5)).
.I Cron
then wakes up every minute, examining all stored crontabs, checking each
command to see if it should be run in the current minute.  When executing
commands, any output is mailed to the owner of the crontab (or to the user
named in the MAILTO environment variable in the crontab, if such exists).
.PP
Additionally,
.I cron
checks each minute to see if its spool directory's modtime (or the modtime
on
.IR /etc/crontab)
has changed, and if it has,
.I cron
will then examine the modtime on all crontabs and reload those which have
changed.  Thus
.I cron
need not be restarted whenever a crontab file is modified.  Note that the
.IR Crontab (1)
command updates the modtime of the spool directory whenever it changes a
crontab.
.SH "SEE ALSO"
crontab(1), crontab(5)
.SH AUTHOR
.nf
Paul Vixie <[e-mail]>