📄 ch28_11.htm
字号:
<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 28] 28.11 cmp and diff </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="1998-08-04T21:44:49Z"><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_10.htm"TITLE="28.10 Problems with diff and Tabstops "><LINKREL="next"HREF="ch28_12.htm"TITLE="28.12 Comparing Two Files with comm "></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_10.htm"TITLE="28.10 Problems with diff and Tabstops "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 28.10 Problems with diff and Tabstops "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_12.htm"TITLE="28.12 Comparing Two Files with comm "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 28.12 Comparing Two Files with comm "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-2700">28.11 cmp and diff </A></H2><TABLECLASS="para.programreference"BORDER="1"><TR><THVALIGN="TOP"><ACLASS="programreference"HREF="examples/index.htm"TITLE="cmp">cmp</A><BR></TH><TDVALIGN="TOP"><ACLASS="indexterm"NAME="AUTOID-31498"></A><ACLASS="indexterm"NAME="AUTOID-31500"></A><EMCLASS="emphasis">cmp</EM> is another program for comparing files.(There's also a GNU version on the CD-ROM.)It's a lot simpler than<SPANCLASS="link"><EMCLASS="emphasis">diff</EM> (<ACLASS="linkend"HREF="ch28_01.htm#UPT-ART-2680"TITLE="Checking Differences with diff ">28.1</A>)</SPAN>;it tells you whether the files are equivalent, and the byte offset at which the firstdifference occurs. You don't get a detailed analysis of where the twofiles differ.For this reason, <EMCLASS="emphasis">cmp</EM> is often faster,particularly when you're comparing<SPANCLASS="link">ASCII (<ACLASS="linkend"HREF="ch51_03.htm"TITLE="ASCII Characters: Listing and Getting Values ">51.3</A>)</SPAN>files: it doesn't have togenerate a long report summarizing the differences.If all you wantto know is whether two files are different, it's the righttool for the job.</TD></TR></TABLE><PCLASS="para">It's worth noting, though, that <EMCLASS="emphasis">cmp</EM> isn't <EMCLASS="emphasis">always</EM> faster.Some versions of <EMCLASS="emphasis">diff</EM> make some simple checks first, likecomparing file length. If two binary files have different lengths,they are obviously different; some <EMCLASS="emphasis">diff</EM> implementations willtell you so without doing any further processing.</P><PCLASS="para">Both <EMCLASS="emphasis">diff</EM> and <EMCLASS="emphasis">cmp</EM> return an <SPANCLASS="link">exit status (<ACLASS="linkend"HREF="ch44_07.htm"TITLE="Exit Status of UNIX Processes ">44.7</A>)</SPAN><EMCLASS="emphasis">cmp</EM>that shows what they found:<TABLECLASS="informaltable"><THEADCLASS="thead"><TRCLASS="row"VALIGN="TOP"><THCLASS="entry"ALIGN="LEFT"ROWSPAN="1"COLSPAN="1">Exit Status</TH><THCLASS="entry"ALIGN="LEFT"ROWSPAN="1"COLSPAN="1">Meaning</TH></TR></THEAD><TBODYCLASS="tbody"><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">0</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">The files were the same.</TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">1</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">The files differed.</TD></TR><TRCLASS="row"VALIGN="TOP"><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">2</TD><TDCLASS="entry"ROWSPAN="1"COLSPAN="1">An error occurred.</TD></TR></TBODY></TABLE>Within a shell script, the exit status from <EMCLASS="emphasis">diff</EM> and<EMCLASS="emphasis">cmp</EM> is often more important than their actual output.</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">ML</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_10.htm"TITLE="28.10 Problems with diff and Tabstops "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 28.10 Problems with diff and Tabstops "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_12.htm"TITLE="28.12 Comparing Two Files with comm "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 28.12 Comparing Two Files with comm "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">28.10 Problems with diff and Tabstops </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">28.12 Comparing Two Files with comm </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
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -