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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 40] Delayed Execution</TITLE><METANAME="DC.title"CONTENT="UNIX Power Tools"><METANAME="DC.creator"CONTENT="Jerry Peek, Tim O'Reilly & Mike Loukides"><METANAME="DC.publisher"CONTENT="O'Reilly & Associates, Inc."><METANAME="DC.date"CONTENT="1998-08-04T21:50:32Z"><METANAME="DC.type"CONTENT="Text.Monograph"><METANAME="DC.format"CONTENT="text/html"SCHEME="MIME"><METANAME="DC.source"CONTENT="1-56592-260-3"SCHEME="ISBN"><METANAME="DC.language"CONTENT="en-US"><METANAME="generator"CONTENT="Jade 1.1/O'Reilly DocBook 3.0 to HTML 4.0"><LINKREV="made"HREF="mailto:online-books@oreilly.com"TITLE="Online Books Comments"><LINKREL="up"HREF="part06.htm"TITLE="VI. Managing Processes "><LINKREL="prev"HREF="ch39_12.htm"TITLE="39.12 What Makes Your Computer Slow? How Do You Fix It?"><LINKREL="next"HREF="ch40_02.htm"TITLE="40.2 Waiting a Little While: sleep "></HEAD><BODYBGCOLOR="#FFFFFF"TEXT="#000000"><DIVCLASS="htmlnav"><H1><IMGSRC="gifs/smbanner.gif"ALT="UNIX Power Tools"USEMAP="#srchmap"BORDER="0"></H1><MAPNAME="srchmap"><AREASHAPE="RECT"COORDS="0,0,466,58"HREF="index.htm"ALT="UNIX Power Tools"><AREASHAPE="RECT"COORDS="467,0,514,18"HREF="jobjects/fsearch.htm"ALT="Search this book"></MAP><TABLEWIDTH="515"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch39_12.htm"TITLE="39.12 What Makes Your Computer Slow? How Do You Fix It?"><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 39.12 What Makes Your Computer Slow? How Do You Fix It?"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 40</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch40_02.htm"TITLE="40.2 Waiting a Little While: sleep "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 40.2 Waiting a Little While: sleep "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="CHAPTER"><H1CLASS="chapter"><ACLASS="title"NAME="UPT-CHP-40">40. Delayed Execution</A></H1><DIVCLASS="htmltoc"><P><B>Contents:</B><BR><ACLASS="sect1"HREF="#UPT-ART-2313"TITLE="40.1 Off-Peak Job Submission ">Off-Peak Job Submission </A><BR><ACLASS="sect1"HREF="ch40_02.htm"TITLE="40.2 Waiting a Little While: sleep ">Waiting a Little While: sleep </A><BR><ACLASS="sect1"HREF="ch40_03.htm"TITLE="40.3 The at Command ">The at Command </A><BR><ACLASS="sect1"HREF="ch40_04.htm"TITLE="40.4 Choosing the Shell Run (We Hope) by at ">Choosing the Shell Run (We Hope) by at </A><BR><ACLASS="sect1"HREF="ch40_05.htm"TITLE="40.5 Avoiding Other at and cron Jobs ">Avoiding Other at and cron Jobs </A><BR><ACLASS="sect1"HREF="ch40_06.htm"TITLE="40.6 System V.4 Batch Queues ">System V.4 Batch Queues </A><BR><ACLASS="sect1"HREF="ch40_07.htm"TITLE="40.7 Making Your at Jobs Quiet ">Making Your at Jobs Quiet </A><BR><ACLASS="sect1"HREF="ch40_08.htm"TITLE="40.8 Automatically Restarting at Jobs ">Automatically Restarting at Jobs </A><BR><ACLASS="sect1"HREF="ch40_09.htm"TITLE="40.9 Checking and Removing Jobs ">Checking and Removing Jobs </A><BR><ACLASS="sect1"HREF="ch40_10.htm"TITLE="40.10 nextday, nextweekday: Tomorrow or Next Weekday ">nextday, nextweekday: Tomorrow or Next Weekday </A><BR><ACLASS="sect1"HREF="ch40_11.htm"TITLE="40.11 Send Yourself Reminder Mail ">Send Yourself Reminder Mail </A><BR><ACLASS="sect1"HREF="ch40_12.htm"TITLE="40.12 Periodic Program Execution: The cron Facility ">Periodic Program Execution: The cron Facility </A><BR><ACLASS="sect1"HREF="ch40_13.htm"TITLE="40.13 Adding crontab Entries ">Adding crontab Entries </A><BR><ACLASS="sect1"HREF="ch40_14.htm"TITLE="40.14 Including Standard Input Within a cron Entry ">Including Standard Input Within a cron Entry </A><BR><ACLASS="sect1"HREF="ch40_15.htm"TITLE="40.15 crontab Script Makes crontab Editing Easier/Safer ">crontab Script Makes crontab Editing Easier/Safer </A></P><P></P></DIV><DIVCLASS="sect1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-2313">40.1 Off-Peak Job Submission </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-44419"></A><ACLASS="indexterm"NAME="AUTOID-44422"></A>Now that time sharing and interactive programming have become universal, many UNIX users have forgotten one of the best ways to get the most outof the system: running jobs at nights or on the weekend. Mostpeople tend to work from 9 to 5, which is roughly one-third of theday. (Though many programmers do keep later hours!)If you can make use of the other hours (night and weekends), youcan almost quadruple your system's throughput. Running jobs at night isless fun than running them interactively, but it is a lot less expensivethan three new machines. If you can useoff-peak hours, you will get a lot more work from your hardware.</P><PCLASS="para">There are a few mechanisms to take advantage of off-peak hours: </P><ULCLASS="itemizedlist"><LICLASS="listitem"><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-44428"></A>The<SPANCLASS="link"><EMCLASS="emphasis">at</EM> command (<ACLASS="linkend"HREF="ch40_03.htm"TITLE="The at Command ">40.3</A>)</SPAN>lets you submit jobs for execution at an arbitrarylater date; it is standard on almost all UNIX systems. </P></LI><LICLASS="listitem"><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-44434"></A>The <SPANCLASS="link"><EMCLASS="emphasis">batch</EM> command (<ACLASS="linkend"HREF="ch40_06.htm"TITLE="System V.4 Batch Queues ">40.6</A>)</SPAN>,which is available in System V.4 and SunOS 4.1, provides a simple(and simplistic) batch queueing system. Some more fully featured batchsystems are available for other UNIX systems.</P></LI><LICLASS="listitem"><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-44440"></A>Although it serves an entirely different purpose, you should also beaware of the <SPANCLASS="link"><EMCLASS="emphasis">crontab</EM> (<ACLASS="linkend"HREF="ch40_12.htm"TITLE="Periodic Program Execution: The cron Facility ">40.12</A>)</SPAN>facility, which provides a way to schedule jobs for periodic executionon a regular basis.</P></LI><LICLASS="listitem"><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-44446"></A>Finally, don't forget <SPANCLASS="link"><EMCLASS="emphasis">sleep</EM> (<ACLASS="linkend"HREF="ch40_02.htm"TITLE="Waiting a Little While: sleep ">40.2</A>)</SPAN>,which can be helpful if you want to delay or space out execution justa little bit.</P></LI></UL><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">ML</SPAN></P></DIV></DIV></DIV><DIVCLASS="htmlnav"><P></P><HRALIGN="LEFT"WIDTH="515"TITLE="footer"><TABLEWIDTH="515"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch39_12.htm"TITLE="39.12 What Makes Your Computer Slow? 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