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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 40] 40.5 Avoiding Other at and cron Jobs </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="1998-08-04T21:50:36Z"><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="ch40_01.htm"TITLE="40. Delayed Execution"><LINKREL="prev"HREF="ch40_04.htm"TITLE="40.4 Choosing the Shell Run (We Hope) by at "><LINKREL="next"HREF="ch40_06.htm"TITLE="40.6 System V.4 Batch Queues "></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="ch40_04.htm"TITLE="40.4 Choosing the Shell Run (We Hope) by at "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 40.4 Choosing the Shell Run (We Hope) by at "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 40<BR>Delayed Execution</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch40_06.htm"TITLE="40.6 System V.4 Batch Queues "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 40.6 System V.4 Batch Queues "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-2311">40.5 Avoiding Other at and cron Jobs </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-44662"></A><ACLASS="indexterm"NAME="AUTOID-44664"></A><ACLASS="indexterm"NAME="AUTOID-44667"></A><SPANCLASS="link"><EMCLASS="emphasis">atq</EM> and <EMCLASS="emphasis">at -l</EM> (<ACLASS="linkend"HREF="ch40_09.htm"TITLE="Checking and Removing Jobs ">40.9</A>)</SPAN>are more important than they seem. They giveyou a way to decide when to run your jobs. I suggest that youcheck <EMCLASS="emphasis">atq</EM> before picking a time to run your job. If you don't,the system may have a dozen huge jobs starting at midnight or 1 a.m.They will bring the system to its knees when there's no one around tohelp out. Here's an example of what can happen, using the BSD-style<EMCLASS="emphasis">at</EM> commands:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>atq</B></CODE> Rank Execution Date Owner Job# Queue Job Name 1st Sep 12, 1996 01:00 mikel 4529 a trashsys.sh 2nd Sep 12, 1996 01:00 johnt 4531 a flame.sh 3rd Sep 12, 1996 01:00 davek 4532 a stdin 4th Sep 12, 1996 01:00 joek 4533 a troffit 5th Sep 13, 1996 02:00 bobr 4534 a stdin</PRE></BLOCKQUOTE></P><PCLASS="para">Four of the five users happened to pick 1 a.m. as their submission time.Therefore, four big jobs will start in the middle of the night. Willyour system survive? Will any of these be done in the morning? Theseare good questions. Instead of submitting your jobs to runat 1 a.m., at midnight, or at some other integral number, start themat different times, and make them times like 3:48 a.m. If your systemadministrator notices lots of jobs running at the same times on yoursystem, she might delete some of them and ask you to reschedule.</P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-44680"></A><ACLASS="indexterm"NAME="AUTOID-44682"></A>If your system has<SPANCLASS="link">personal <EMCLASS="emphasis">crontab</EM> files (<ACLASS="linkend"HREF="ch40_12.htm"TITLE="Periodic Program Execution: The cron Facility ">40.12</A>)</SPAN>,you won't be able to see other users' <EMCLASS="emphasis">cron</EM> jobs.The best way to cut system load is to pick strange times like 4:37 a.m.for your <EMCLASS="emphasis">cron</EM> jobs.</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">ML</SPAN> <SPANCLASS="bibliomisc">from O'Reilly & Associates' <CITECLASS="citetitle">System Performance Tuning</CITE>, Chapter 3</SPAN></P></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="ch40_04.htm"TITLE="40.4 Choosing the Shell Run (We Hope) by at "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 40.4 Choosing the Shell Run (We Hope) by at "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><ACLASS="book"HREF="index.htm"TITLE="UNIX Power Tools"><IMGSRC="gifs/txthome.gif"SRC="gifs/txthome.gif"ALT="UNIX Power Tools"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch40_06.htm"TITLE="40.6 System V.4 Batch Queues "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 40.6 System V.4 Batch Queues "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">40.4 Choosing the Shell Run (We Hope) by at </TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><ACLASS="index"HREF="index/idx_0.htm"TITLE="Book Index"><IMGSRC="gifs/index.gif"SRC="gifs/index.gif"ALT="Book Index"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172">40.6 System V.4 Batch Queues </TD></TR></TABLE><HRALIGN="LEFT"WIDTH="515"TITLE="footer"><IMGSRC="gifs/smnavbar.gif"SRC="gifs/smnavbar.gif"USEMAP="#map"BORDER="0"ALT="The UNIX CD Bookshelf Navigation"><MAPNAME="map"><AREASHAPE="RECT"COORDS="0,0,73,21"HREF="../index.htm"ALT="The UNIX CD Bookshelf"><AREASHAPE="RECT"COORDS="74,0,163,21"HREF="index.htm"ALT="UNIX Power Tools"><AREASHAPE="RECT"COORDS="164,0,257,21"HREF="../unixnut/index.htm"ALT="UNIX in a Nutshell"><AREASHAPE="RECT"COORDS="258,0,321,21"HREF="../vi/index.htm"ALT="Learning the vi Editor"><AREASHAPE="RECT"COORDS="322,0,378,21"HREF="../sedawk/index.htm"ALT="sed & awk"><AREASHAPE="RECT"COORDS="379,0,438,21"HREF="../ksh/index.htm"ALT="Learning the Korn Shell"><AREASHAPE="RECT"COORDS="439,0,514,21"HREF="../lrnunix/index.htm"ALT="Learning the UNIX Operating System"></MAP></DIV></BODY></HTML>⌨️ 快捷键说明
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