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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 45] 45.33 Testing Two Strings with One case Statement </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="1998-08-04T21:55:15Z"><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="ch45_01.htm"TITLE="45. Shell Programming for the Initiated"><LINKREL="prev"HREF="ch45_32.htm"TITLE="45.32 A Better read Command: grabchars "><LINKREL="next"HREF="ch45_34.htm"TITLE="45.34 Arrays in the Bourne Shell "></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="ch45_32.htm"TITLE="45.32 A Better read Command: grabchars "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 45.32 A Better read Command: grabchars "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 45<BR>Shell Programming for the Initiated</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch45_34.htm"TITLE="45.34 Arrays in the Bourne Shell "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 45.34 Arrays in the Bourne Shell "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-0494">45.33 Testing Two Strings with One case Statement </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-55021"></A><ACLASS="indexterm"NAME="AUTOID-55024"></A><ACLASS="indexterm"NAME="AUTOID-55027"></A><ACLASS="indexterm"NAME="AUTOID-55030"></A><ACLASS="indexterm"NAME="AUTOID-55033"></A><ACLASS="indexterm"NAME="AUTOID-55036"></A><ACLASS="indexterm"NAME="AUTOID-55039"></A><ACLASS="indexterm"NAME="AUTOID-55042"></A>The shell's<SPANCLASS="link"><EMCLASS="emphasis">case</EM> statement (<ACLASS="linkend"HREF="ch44_05.htm"TITLE="Test String Values with Bourne Shell case ">44.5</A>)</SPAN>has some advantages over the <SPANCLASS="link"><EMCLASS="emphasis">test</EM> command (<ACLASS="linkend"HREF="ch44_20.htm"TITLE="test: Testing Files and Strings ">44.20</A>)</SPAN>-for instance, <EMCLASS="emphasis">case</EM> can do pattern matching.But <EMCLASS="emphasis">test</EM> has the <EMCLASS="emphasis">-a</EM> and <EMCLASS="emphasis">-o</EM> "and" and "or" operators;those don't seem easy to do with <EMCLASS="emphasis">case</EM>.And <EMCLASS="emphasis">test</EM> isn't built in to some older shells, so using <EMCLASS="emphasis">case</EM>may be faster.</P><PCLASS="para">Here's a way to test two things with one <EMCLASS="emphasis">case</EM> statement.It won't solve all your problems.If you think carefully about the possible values the variables you'retesting can have, though, this might do the trick.Use a separator (delimiter) character between the two variables.</P><PCLASS="para">In the example below, I've picked a slash (<CODECLASS="literal">/</CODE>).You could use almost any character that isn't used in<SPANCLASS="link"><EMCLASS="emphasis">case</EM> pattern matching (<ACLASS="linkend"HREF="ch44_06.htm"TITLE="Pattern Matching in case Statements ">44.6</A>)</SPAN>and that won't be stored in either <CODECLASS="literal">$#</CODE> or <CODECLASS="literal">$1</CODE>.The <EMCLASS="emphasis">case</EM> below tests the command-line arguments of a script:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">case "$#/$1" in1/-f) redodb=yes ;;0/) ;;*) echo "Usage: $myname [-f]" 1>&2; exit 1 ;;esac</PRE></BLOCKQUOTE></P><PCLASS="para">If there's one argument (<CODECLASS="literal">$#</CODE> is <CODECLASS="literal">1</CODE>) and the argument(<CODECLASS="literal">$1</CODE>) is exactly <CODECLASS="literal">-f</CODE>, the first pattern matches, and the<EMCLASS="emphasis">redodb</EM> variable is set.If there's no argument, <CODECLASS="literal">$#</CODE> will be <CODECLASS="literal">0</CODE> and <CODECLASS="literal">$1</CODE> willbe empty, so the second pattern matches.Otherwise, something is wrong; the third pattern matches, the scriptprints an error and exits.</P><PCLASS="para">Of course, you can do a lot more this way than just testing command-linearguments.</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="ch45_32.htm"TITLE="45.32 A Better read Command: grabchars "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 45.32 A Better read Command: grabchars "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="ch45_34.htm"TITLE="45.34 Arrays in the Bourne Shell "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 45.34 Arrays in the Bourne Shell "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">45.32 A Better read Command: grabchars </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">45.34 Arrays in the Bourne Shell </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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