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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 8] 8.18 Here Documents </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="1998-08-04T21:34:35Z"><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="ch08_01.htm"TITLE="8. How the Shell Interprets What You Type"><LINKREL="prev"HREF="ch08_17.htm"TITLE="8.17 verbose and echo Variables Show Quoting "><LINKREL="next"HREF="ch08_19.htm"TITLE='8.19 "Special" Characters and Operators '></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="ch08_17.htm"TITLE="8.17 verbose and echo Variables Show Quoting "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 8.17 verbose and echo Variables Show Quoting "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 8<BR>How the Shell Interprets What You Type</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch08_19.htm"TITLE='8.19 "Special" Characters and Operators '><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT='Next: 8.19 "Special" Characters and Operators 'BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-7799">8.18 Here Documents </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-8848"></A>So far, we've talked about three different kinds of quoting:backslashes (<CODECLASS="literal">\</CODE>), single quotes (<CODECLASS="literal">'</CODE>), and double quotes(<CODECLASS="literal"><"></CODE>).The shells support yet one more kind of quoting, called <EMCLASS="emphasis">here documents</EM>. A here document is useful when you need to read something from standard input, but you don'twant to create a file to provide that input; you want to put thatinput right into your shell script (or type it directly on the command line).To do so, use the <ACLASS="indexterm"NAME="AUTOID-8854"></A><CODECLASS="literal"><<</CODE>operator, followed by a special word:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">sort >file <<EndOfSortzygoteabacusEndOfSort</PRE></BLOCKQUOTE></P><PCLASS="para">This is very useful because<SPANCLASS="link">variables (<ACLASS="linkend"HREF="ch06_08.htm"TITLE="Shell Variables ">6.8</A>, <ACLASS="linkend"HREF="ch06_01.htm#UPT-ART-1170"TITLE="What Environment Variables Are Good For ">6.1</A>)</SPAN>are evaluatedduring this operation.<ACLASS="indexterm"NAME="AUTOID-8862"></A>Here is a way to transfer a file using anonymous<SPANCLASS="link"><EMCLASS="emphasis">ftp</EM> (<ACLASS="linkend"HREF="ch52_07.htm"TITLE="Other Ways to Get the Software ">52.7</A>)</SPAN>from a shell script:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen"> #!/bin/sh# Usage:# ftpfile machine file# set -xSOURCE=$1FILE=$2GETHOST="uname -n"BFILE=`basename $FILE`ftp -n $SOURCE <<EndFTPasciiuser anonymous $USER@`$GETHOST`get $FILE /tmp/$BFILEEndFTP</PRE></BLOCKQUOTE></P><PCLASS="para">As you can see, variables and<SPANCLASS="link">command substitutions (<ACLASS="linkend"HREF="ch09_16.htm"TITLE="Command Substitution ">9.16</A>)</SPAN>are done.If you don't want those to be done,put a backslash in front of the name of the word:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">cat >file <<\FunkyStriNG</PRE></BLOCKQUOTE></P><PCLASS="para">Notice the funky string. This is done becauseit is very unlikely that I will want to put that particularcombination ofcharacters in any file.<ACLASS="indexterm"NAME="AUTOID-8874"></A>You should be warned that the C shell expects thematching word (at the end of the list) to be escaped the same way, i.e.,<CODECLASS="literal">\FunkyStriNG</CODE>,while the Bourne shell does not. See article<ACLASS="xref"HREF="ch45_26.htm"TITLE="Quoted hereis Document Terminators: sh vs. csh ">45.26</A>.</P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-8880"></A><ACLASS="indexterm"NAME="AUTOID-8883"></A><ACLASS="indexterm"NAME="AUTOID-8886"></A><ACLASS="indexterm"NAME="AUTOID-8889"></A>[Most Bourne shells also have the <CODECLASS="literal"><<-</CODE> operator.The dash (<CODECLASS="literal">-</CODE>) at the end tells the shell to strip any TABcharacters from the beginning of each line.Use this in shell scripts to indent a section of text withoutpassing those TABs to the command's standard input. <EMCLASS="emphasis">-JP</EM>]</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">BB</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="ch08_17.htm"TITLE="8.17 verbose and echo Variables Show Quoting "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 8.17 verbose and echo Variables Show Quoting "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="ch08_19.htm"TITLE='8.19 "Special" Characters and Operators '><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT='Next: 8.19 "Special" Characters and Operators 'BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">8.17 verbose and echo Variables Show Quoting </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">8.19 "Special" Characters and Operators </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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