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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 27] 27.9 New greps Are Much Faster </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="1998-08-04T21:44:24Z"><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="ch27_01.htm"TITLE="27. Searching Through Files"><LINKREL="prev"HREF="ch27_08.htm"TITLE="27.8 glimpse and agrep "><LINKREL="next"HREF="ch27_10.htm"TITLE="27.10 Search RCS Files with rcsgrep "></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="ch27_08.htm"TITLE="27.8 glimpse and agrep "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 27.8 glimpse and agrep "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 27<BR>Searching Through Files</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch27_10.htm"TITLE="27.10 Search RCS Files with rcsgrep "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 27.10 Search RCS Files with rcsgrep "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-7590">27.9 New greps Are Much Faster </A></H2><TABLECLASS="para.programreference"BORDER="1"><TR><THVALIGN="TOP"><ACLASS="programreference"HREF="examples/index.htm"TITLE="grep">grep</A><BR></TH><TDVALIGN="TOP"><ACLASS="indexterm"NAME="AUTOID-30332"></A><ACLASS="indexterm"NAME="AUTOID-30335"></A><ACLASS="indexterm"NAME="AUTOID-30339"></A><ACLASS="indexterm"NAME="AUTOID-30341"></A><ACLASS="indexterm"NAME="AUTOID-30343"></A><ACLASS="indexterm"NAME="AUTOID-30345"></A>Many of the newer, public domain greps such as<SPANCLASS="link"><EMCLASS="emphasis">agrep</EM> (<ACLASS="linkend"HREF="ch27_08.htm"TITLE="glimpse and agrep ">27.8</A>)</SPAN>andGNU <EMCLASS="emphasis">egrep</EM>, use the much fasterBoyer-Moore search algorithm.Both <EMCLASS="emphasis">agrep</EM> and GNU <EMCLASS="emphasis">egrep</EM>are on the CD-ROM. [1] </TD></TR></TABLE><BLOCKQUOTECLASS="footnote"><PCLASS="para">[1] The GNU <EMCLASS="emphasis">egrep</EM> executable is alsoinstalled under the name <EMCLASS="emphasis">grep</EM>-so don't get confused!</P></BLOCKQUOTE><PCLASS="para">In article <ACLASS="xref"HREF="ch27_06.htm"TITLE="Fast grep Isn't ">27.6</A>,we used the<SPANCLASS="link"><EMCLASS="emphasis">runtime</EM> program (<ACLASS="linkend"HREF="ch39_04.htm"TITLE="Average Command Runtimes with runtime ">39.4</A>)</SPAN>to compare the execution times of<EMCLASS="emphasis">fgrep</EM>, <EMCLASS="emphasis">egrep</EM>, and <EMCLASS="emphasis">grep</EM>. This time we'll use<EMCLASS="emphasis">runtime</EM>to show the average time needed to search for the string <EMCLASS="emphasis">Waldo</EM> in a large directory of files. First, let's showthe results using <EMCLASS="emphasis">agrep</EM>:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>runtime -10 agrep Waldo *</B></CODE> ...AVERAGES: 0.48u 0.73s 0:01 0+261k 0+0io 0pf+0w</PRE></BLOCKQUOTE></P><PCLASS="para">Here's the same output for GNU <EMCLASS="emphasis">egrep</EM>:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>runtime -10 egrep Waldo *</B></CODE> ...AVERAGES: 0.62u 0.62s 0:01 0+242k 0+0io 0pf+0w</PRE></BLOCKQUOTE></P><PCLASS="para">Now compare these numbers against those in article <ACLASS="xref"HREF="ch27_06.htm"TITLE="Fast grep Isn't ">27.6</A>.For example, here's what we get from the much-maligned everyday <EMCLASS="emphasis">grep</EM>:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>runtime -10 grep Waldo *</B></CODE> ...AVERAGES: 4.13u 0.83s 0:04 0+203k 21+0io 19pf+0w</PRE></BLOCKQUOTE></P><PCLASS="para"><EMCLASS="emphasis">grep</EM> took four clock seconds to searchall the files, while both <EMCLASS="emphasis">agrep</EM> and GNU <EMCLASS="emphasis">egrep</EM> breezed by inone.So are you a believer yet?</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">TOR</SPAN>, <SPANCLASS="authorinitials">LM</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="ch27_08.htm"TITLE="27.8 glimpse and agrep "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 27.8 glimpse and agrep "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="ch27_10.htm"TITLE="27.10 Search RCS Files with rcsgrep "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 27.10 Search RCS Files with rcsgrep "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">27.8 glimpse and agrep </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">27.10 Search RCS Files with rcsgrep </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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