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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 27] 27.5 Extended Searching for Text with egrep </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="1998-08-04T21:44:20Z"><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_04.htm"TITLE="27.4 Finding a Pattern Only When It's a Word "><LINKREL="next"HREF="ch27_06.htm"TITLE="27.6 Fast grep Isn't "></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_04.htm"TITLE="27.4 Finding a Pattern Only When It's a Word "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 27.4 Finding a Pattern Only When It's a Word "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_06.htm"TITLE="27.6 Fast grep Isn't "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 27.6 Fast grep Isn't "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-2560">27.5 Extended Searching for Text with egrep </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-30071"></A><ACLASS="indexterm"NAME="AUTOID-30075"></A><ACLASS="indexterm"NAME="AUTOID-30078"></A><ACLASS="indexterm"NAME="AUTOID-30081"></A>The <EMCLASS="emphasis">egrep</EM> command is yet another version of<SPANCLASS="link"><EMCLASS="emphasis">grep</EM> (<ACLASS="linkend"HREF="ch27_02.htm"TITLE="Searching for Text with grep ">27.2</A>)</SPAN>,one that extends<SPANCLASS="link">the syntax of regular expressions (<ACLASS="linkend"HREF="ch26_04.htm"TITLE="Using Metacharacters in Regular Expressions ">26.4</A>)</SPAN>.A plus sign (<CODECLASS="literal">+</CODE>) following a regular expression matches one or moreoccurrences of the regular expression; a question mark (<CODECLASS="literal">?</CODE>)matches zero or one occurrences.In addition, regular expressions can be nested within parentheses:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>egrep "Lab(oratorie)?s" name.list</B></CODE>AT&T Bell LaboratoriesAT&T Bell LabsSymtel Labs of Chicago</PRE></BLOCKQUOTE></P><PCLASS="para">Parentheses surround a second regular expression and <CODECLASS="literal">?</CODE> modifies thisexpression.The nesting helps to eliminate unwanted matches; for instance, theword <EMCLASS="emphasis">Labors</EM> or <EMCLASS="emphasis">oratories</EM> would not be matched.</P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-30097"></A>Another special feature of <EMCLASS="emphasis">egrep</EM> is the vertical bar (<CODECLASS="literal">|</CODE>), whichserves as an <EMCLASS="emphasis">or</EM> operator between two expressions.Lines matching either expression are printed, as inthe next example:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>egrep "stdscr|curscr" ch03</B></CODE>into the stdscr, a character array.When stdscr is refreshed, thestdscr is refreshed.curscr.initscr() creates two windows: stdscrand curscr.</PRE></BLOCKQUOTE></P><PCLASS="para">Remember to put the expression inside quotation marks to protect thevertical bar from being interpreted by the shell as a pipe symbol.Look at the next example:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>egrep "Alcuin (User|Programmer)('s)? Guide" docguide</B></CODE>Alcuin Progammer's Guide is a thoroughrefer to the Alcuin User GuideAlcuin User's Guide introduces new users to</PRE></BLOCKQUOTE></P><PCLASS="para">You can see the flexibility that <EMCLASS="emphasis">egrep</EM>'s syntax can give you,matching either <CODECLASS="literal">User</CODE> or <CODECLASS="literal">Programmer</CODE> and matching them whether or not they hadan <CODECLASS="literal">'s</CODE>.Article<ACLASS="xref"HREF="ch20_08.htm"TITLE="Telling tar Which Files to Exclude or Include ">20.8</A>has another example and explanation of <EMCLASS="emphasis">egrep</EM>.</P><PCLASS="para">Both <EMCLASS="emphasis">egrep</EM> and<SPANCLASS="link"><EMCLASS="emphasis">fgrep</EM> (<ACLASS="linkend"HREF="ch27_06.htm"TITLE="Fast grep Isn't ">27.6</A>)</SPAN>can read search patterns from a file usingthe<SPANCLASS="link"><EMCLASS="emphasis">-f</EM> option (<ACLASS="linkend"HREF="ch27_07.htm"TITLE="grepping for a List of Patterns ">27.7</A>)</SPAN>.The<SPANCLASS="link"><EMCLASS="emphasis">calendar</EM> (<ACLASS="linkend"HREF="ch48_04.htm"TITLE="Automatic Reminders and More: calendar ">48.4</A>)</SPAN>utility makes a file full of complicated expressions for matching dates.</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">DD</SPAN> <SPANCLASS="bibliomisc">from <CITECLASS="citetitle">UNIX Text Processing</CITE>, Hayden Books, 1987, Chapter 11</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_04.htm"TITLE="27.4 Finding a Pattern Only When It's a Word "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 27.4 Finding a Pattern Only When It's a Word "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_06.htm"TITLE="27.6 Fast grep Isn't "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 27.6 Fast grep Isn't "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">27.4 Finding a Pattern Only When It's a Word </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">27.6 Fast grep Isn't </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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