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<A NAME="353"> </A><H2><A NAME="SECTION00334000000000000000">Periodic command execution: <tt>cron</tt><A NAME="351"> </A> and <tt>at</tt></A></H2>
<P>
Both users and system administrators often need to run
commands periodically. For example, the system
administrator might want to run a command to clean the
directories with temporary files (<tt>/tmp</tt><A NAME="355"> </A> and <tt>/var/tmp</tt><A NAME="357"> </A>)
from old files, to keep the disks from filling up, since not
all programs clean up after themselves correctly.
<A NAME="287"> </A>
<A NAME="211"> </A>
<A NAME="212"> </A>
<P>
The <tt>cron</tt><A NAME="359"> </A> service is set up to do this. Each user has
a <tt>crontab</tt><A NAME="361"> </A>, where he lists the commands he wants to
execute and the times they should be executed. The <tt>cron</tt><A NAME="363"> </A>
daemon takes care of starting the commands when specified.
<A NAME="288"> </A>
<P>
The <tt>at</tt><A NAME="365"> </A> service is similar to <tt>cron</tt><A NAME="367"> </A>, but it is
once only: the command is executed at the given time, but it
is not repeated.
<A NAME="289"> </A>
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<P><ADDRESS>
<I>Lars Wirzenius <BR>
Sat Nov 15 02:32:11 EET 1997</I>
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