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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 33] 33.7 ed/ex Batch Edits: Avoid Errors When No Match </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="1998-08-04T21:46:53Z"><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="ch33_01.htm"TITLE="33. Batch Editing"><LINKREL="prev"HREF="ch33_06.htm"TITLE="33.6 Change Many Files by Editing Just One "><LINKREL="next"HREF="ch33_08.htm"TITLE="33.8 Batch Editing Gotcha: Editors Bomb on Big Files "></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="ch33_06.htm"TITLE="33.6 Change Many Files by Editing Just One "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 33.6 Change Many Files by Editing Just One "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 33<BR>Batch Editing</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch33_08.htm"TITLE="33.8 Batch Editing Gotcha: Editors Bomb on Big Files "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 33.8 Batch Editing Gotcha: Editors Bomb on Big Files "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-0153">33.7 ed/ex Batch Edits: Avoid Errors When No Match </A></H2><DIVCLASS="msgset"><DIVCLASS="msgentry"><DIVCLASS="msg"><DIVCLASS="msgtext"><PCLASS="para"><BCLASS="msgentry.role">Q:</B> My <SPANCLASS="link">Bourne shell script (<ACLASS="linkend"HREF="ch44_01.htm#UPT-ART-0065"TITLE="Everyone Should Learn Some Shell Programming ">44.1</A>)</SPAN>calls <EMCLASS="emphasis">ed</EM> to edit a set of files:</P><PCLASS="para"><BCLASS="msgentry.role">Q:</B> <TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"><ACLASS="co"HREF="ch06_08.htm"TITLE="6.8 Shell Variables ">=</A> <ACLASS="co"HREF="ch09_12.htm"TITLE="9.12 The Bourne Shell for Loop ">for</A> <ACLASS="co"HREF="ch08_18.htm"TITLE="8.18 Here Documents "><<</A> <ACLASS="co"HREF="ch08_14.htm"TITLE="8.14 Bourne Shell Quoting ">\</A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen">site=somethingcmty=somethingelsefor i in file1 file2 file3do ed $i << end 1,\$s/pat1/$site/g 1,\$s/pat2/$cmty/g w qenddone</PRE></TD></TR></TABLE></P><PCLASS="para"><BCLASS="msgentry.role">Q:</B> <ACLASS="indexterm"NAME="AUTOID-36875"></A><ACLASS="indexterm"NAME="AUTOID-36878"></A><ACLASS="indexterm"NAME="AUTOID-36881"></A>It works fine except when one of the files does not contain <EMCLASS="emphasis">pat1</EM>.<EMCLASS="emphasis">ed</EM> doesn't update that file, even though it could have matched <EMCLASS="emphasis">pat2</EM>.The other files are edited as they should be.</P></DIV></DIV></DIV><DIVCLASS="msgentry"><DIVCLASS="msg"><DIVCLASS="msgtext"><PCLASS="para"><BCLASS="msgentry.role">A:</B> On an error - including "no matches" - <EMCLASS="emphasis">ed</EM> attempts todiscard any unread commands. If you are running <EMCLASS="emphasis">ed</EM> "by hand"this has no effect, but if its input is from a file, this makesEOF -d-of-file) the next thing it sees. You could remove the <CODECLASS="literal">q</CODE>command and you would see the same behavior, as <EMCLASS="emphasis">ed</EM> automatically quitsat end-of-file.</P></DIV></DIV></DIV></DIV><PCLASS="para">There is a simple workaround. Unlike the <CODECLASS="literal">s</CODE> command, the<EMCLASS="emphasis">global</EM> command <CODECLASS="literal">g</CODE> does not report an error if no lines match.Thus:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">ed - $i << endg/pat1/s//$site/gg/pat2/s//$cmty/gwend</PRE></BLOCKQUOTE></P><PCLASS="para">The <EMCLASS="emphasis">-</EM> (dash) flag suppresses the two numbersthat <EMCLASS="emphasis">ed</EM> normally prints when reading and writing files.These are the number of characters in the file,and are usually irrelevant.[As Chris explained, the <CODECLASS="literal">q</CODE> in the original script isn't needed.<EMCLASS="emphasis">-JP</EM> ]</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">CT</SPAN> <SPANCLASS="bibliomisc">in <ACLASS="systemitem.newsgroup"HREF="news:comp.unix.questions">comp.unix.questions</A> on Usenet, 16 May 1989</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="ch33_06.htm"TITLE="33.6 Change Many Files by Editing Just One "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 33.6 Change Many Files by Editing Just One "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="ch33_08.htm"TITLE="33.8 Batch Editing Gotcha: Editors Bomb on Big Files "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 33.8 Batch Editing Gotcha: Editors Bomb on Big Files "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">33.6 Change Many Files by Editing Just One </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">33.8 Batch Editing Gotcha: Editors Bomb on Big Files </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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