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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 40] 40.14 Including Standard Input Within a cron Entry </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="1998-08-04T21:50:48Z"><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_13.htm"TITLE="40.13 Adding crontab Entries "><LINKREL="next"HREF="ch40_15.htm"TITLE="40.15 crontab Script Makes crontab Editing Easier/Safer "></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_13.htm"TITLE="40.13 Adding crontab Entries "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 40.13 Adding crontab Entries "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_15.htm"TITLE="40.15 crontab Script Makes crontab Editing Easier/Safer "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 40.15 crontab Script Makes crontab Editing Easier/Safer "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-5412">40.14 Including Standard Input Within a cron Entry </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-45247"></A>Since <EMCLASS="emphasis">crontab</EM> entries must be a single line long, it's hard toinclude any standard input with them.Sure, you can use commands like:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">0 22 * * * echo "It's 10PM; do you know where your children are?" | wall</PRE></BLOCKQUOTE></P><PCLASS="para">but you can't use "here documents" and other methods of generatingmultiline input; they intrinsically take several lines.</P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-45255"></A>To solve this problem, <EMCLASS="emphasis">cron</EM> allows you to include standardinput directly on the command line.If the command contains a percent sign (<CODECLASS="literal">%</CODE>), <EMCLASS="emphasis">cron</EM> uses any textfollowing the sign as standard input for <EMCLASS="emphasis">cmd</EM>. Additional percentsigns can be used to subdivide this text into lines. For example, thefollowing <EMCLASS="emphasis">crontab</EM> entry:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">30 11 31 12 * /etc/wall%Happy New Year!%Let's make next year great!</PRE></BLOCKQUOTE></P><PCLASS="para"> runs the <EMCLASS="emphasis">wall</EM> command at 11:30 a.m. on December 31st, using the text:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">Happy New Year!Let's make next year great!</PRE></BLOCKQUOTE></P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-45270"></A>as standard input.[If you need a literal percent sign in your entry, for a command like<CODECLASS="literal">date +%a</CODE>, escape the percent sign with a backslash: <CODECLASS="literal">\%</CODE>.<EMCLASS="emphasis">-JP</EM> ]</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">AF</SPAN> <SPANCLASS="bibliomisc">from O'Reilly & Associates' <CITECLASS="citetitle">Essential System Administration</CITE></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_13.htm"TITLE="40.13 Adding crontab Entries "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 40.13 Adding crontab Entries "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_15.htm"TITLE="40.15 crontab Script Makes crontab Editing Easier/Safer "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 40.15 crontab Script Makes crontab Editing Easier/Safer "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">40.13 Adding crontab Entries </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">40.15 crontab Script Makes crontab Editing Easier/Safer </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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