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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 40] 40.7 Making Your at Jobs Quiet </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="1998-08-04T21:50:37Z"><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_06.htm"TITLE="40.6 System V.4 Batch Queues "><LINKREL="next"HREF="ch40_08.htm"TITLE="40.8 Automatically Restarting at Jobs "></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_06.htm"TITLE="40.6 System V.4 Batch Queues "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 40.6 System V.4 Batch Queues "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_08.htm"TITLE="40.8 Automatically Restarting at Jobs "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 40.8 Automatically Restarting at Jobs "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-0058">40.7 Making Your at Jobs Quiet </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-44727"></A><ACLASS="indexterm"NAME="AUTOID-44730"></A>Most modern versions of <EMCLASS="emphasis">at</EM> will<SPANCLASS="link">mail (<ACLASS="linkend"HREF="ch01_33.htm"TITLE="UNIX Networking and Communications ">1.33</A>)</SPAN>you any output that yourcommands make.Some people try the command line below to throw that output into the UNIXtrash can,<SPANCLASS="link"><EMCLASS="emphasis">/dev/null</EM> (<ACLASS="linkend"HREF="ch13_14.htm"TITLE="What Can You Do with an Empty File? ">13.14</A>)</SPAN>:</P><PCLASS="para"><TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"><ACLASS="co"HREF="ch13_05.htm"TITLE="13.5 Redirection in C Shell: Capture Errors, Too? ">>&</A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen">% <CODECLASS="userinput"><B>at \f[CBO]sometime... >& /dev/null</B></CODE> <ICLASS="lineannotation">...wrong</I></PRE></TD></TR></TABLE></P><PCLASS="para">But that won't work because it throws away the output of the <EMCLASS="emphasis">at</EM>command itself.<EMCLASS="emphasis">at</EM> just saves your job in a file to be run later by a system program.The commands you want quiet are the commands stored in that file.One way to keep <EMCLASS="emphasis">at</EM> quiet, if you use the C shell, is:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>at </B></CODE><CODECLASS="replaceable"><I>sometime</I></CODE><CODECLASS="userinput"><B>...</B></CODE>at> <CODECLASS="replaceable"><I>some command</I></CODE><CODECLASS="userinput"><B> >& /dev/null</B></CODE>at> <CODECLASS="replaceable"><I>another command</I></CODE><CODECLASS="userinput"><B> >& /dev/null</B></CODE>at> <CODECLASS="replaceable"><I>...etc...</I></CODE><CODECLASS="userinput"><B> >& /dev/null</B></CODE>at> <KBDCLASS="keycap">[CTRL-d]</KBD></PRE></BLOCKQUOTE></P><PCLASS="para">The Bourne shell makes it easier:</P><PCLASS="para"><TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"> <ACLASS="co"HREF="ch45_07.htm"TITLE="45.7 The exec Command ">exec ></A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen">$ <CODECLASS="userinput"><B>at </B></CODE><CODECLASS="replaceable"><I>sometime</I></CODE><CODECLASS="userinput"><B>...</B></CODE>at> <CODECLASS="userinput"><B>exec ></B></CODE><CODECLASS="userinput"><B> /dev/null 2>&1</B></CODE>at> <CODECLASS="replaceable"><I>some command</I></CODE>at> <CODECLASS="replaceable"><I>another command</I></CODE>at> <CODECLASS="replaceable"><I>...etc...</I></CODE>at> <KBDCLASS="keycap">[CTRL-d]</KBD></PRE></TD></TR></TABLE></P><PCLASS="para">Two notes:</P><ULCLASS="itemizedlist"><LICLASS="listitem"><PCLASS="para">Some versions of <EMCLASS="emphasis">at</EM> have a <EMCLASS="emphasis">-s</EM> option that runs your jobwith the Bourne shell.</P></LI><LICLASS="listitem"><PCLASS="para">Not all versions of <EMCLASS="emphasis">at</EM> prompt you with <CODECLASS="literal">at></CODE> as I showed above.</P></LI></UL><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">JP</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_06.htm"TITLE="40.6 System V.4 Batch Queues "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 40.6 System V.4 Batch Queues "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_08.htm"TITLE="40.8 Automatically Restarting at Jobs "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 40.8 Automatically Restarting at Jobs "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">40.6 System V.4 Batch Queues </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">40.8 Automatically Restarting at Jobs </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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