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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 28] 28.7 diff for Very Long Files: bdiff </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="1998-08-04T21:44:45Z"><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="ch28_01.htm"TITLE="28. Comparing Files"><LINKREL="prev"HREF="ch28_06.htm"TITLE="28.6 Choosing Sides with sdiff "><LINKREL="next"HREF="ch28_08.htm"TITLE="28.8 More Friendly diff Output "></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="ch28_06.htm"TITLE="28.6 Choosing Sides with sdiff "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 28.6 Choosing Sides with sdiff "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 28<BR>Comparing Files</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch28_08.htm"TITLE="28.8 More Friendly diff Output "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 28.8 More Friendly diff Output "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-5820">28.7 diff for Very Long Files: bdiff </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-31291"></A><ACLASS="indexterm"NAME="AUTOID-31293"></A><ACLASS="indexterm"NAME="AUTOID-31296"></A>The <EMCLASS="emphasis">diff</EM> command has trouble comparing very long files.Its <EMCLASS="emphasis">-h</EM> option does a half-hearted and fast job, but it canmiss changes in some cases.System V users have an alternative: <EMCLASS="emphasis">bdiff</EM>.It ignores lines common to the beginning ofboth files, splits the remainder of each file into chunks,and runs <EMCLASS="emphasis">diff</EM> on corresponding segments.(BSD users can probably make a shell script that does this, more or less.I haven't tried, though.)<EMCLASS="emphasis">bdiff</EM> also adjusts the line numbers for each chunk to make itlook like one <EMCLASS="emphasis">diff</EM> did the whole job.</P><PCLASS="para">The good part of this is that <EMCLASS="emphasis">bdiff</EM> will find all the differences.The bad part is that it might find "differences" that really aren'tdifferences at all.This extra output is usually caused by uneven-length files.Here's an example of two files that aren't quite too long for theregular <EMCLASS="emphasis">diff</EM>-it finds the single difference correctly.But <EMCLASS="emphasis">bdiff</EM> finds another "difference" that isn't really a difference:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>diff log1 log2</B></CODE>11580a11581> 15:25:42: ERROR: printer offline% <CODECLASS="userinput"><B>bdiff log1 log2</B></CODE>11580a11581> 15:25:42: ERROR: printer offline15080d15080< 17:22:59: WARNING: queue too long; waiting15080a15081> 17:22:59: WARNING: queue too long; waiting</PRE></BLOCKQUOTE></P><PCLASS="para">Even with that wart, sometimes you can't get along without <EMCLASS="emphasis">bdiff</EM>.</P><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="ch28_06.htm"TITLE="28.6 Choosing Sides with sdiff "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 28.6 Choosing Sides with sdiff "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="ch28_08.htm"TITLE="28.8 More Friendly diff Output "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 28.8 More Friendly diff Output "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">28.6 Choosing Sides with sdiff </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">28.8 More Friendly diff Output </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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