📄 ch47_06.htm

📁 the unix power tools
💻 HTM
字号:
<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 47] 47.6 Quick Reference: C Shell switch Statement </TITLE><METANAME="DC.title"CONTENT="UNIX Power Tools"><METANAME="DC.creator"CONTENT="Jerry Peek, Tim O'Reilly &amp; Mike Loukides"><METANAME="DC.publisher"CONTENT="O'Reilly &amp; Associates, Inc."><METANAME="DC.date"CONTENT="1998-08-04T21:56:03Z"><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="ch47_01.htm"TITLE="47. C Shell Programming...NOT"><LINKREL="prev"HREF="ch47_05.htm"TITLE="47.5 Using C Shell Arrays "><LINKREL="next"HREF="part09.htm"TITLE="IX. Miscellaneous "></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="ch47_05.htm"TITLE="47.5 Using C Shell Arrays "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 47.5 Using C Shell Arrays "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 47<BR>C Shell Programming...NOT</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="PART"HREF="part09.htm"TITLE="IX. Miscellaneous "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: IX. Miscellaneous "BORDER="0"></A></TD></TR></TABLE>&nbsp;<HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-7889">47.6 Quick Reference: C Shell switch Statement </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-57489"></A><ACLASS="indexterm"NAME="AUTOID-57492"></A><ACLASS="indexterm"NAME="AUTOID-57495"></A><ACLASS="indexterm"NAME="AUTOID-57498"></A><ACLASS="indexterm"NAME="AUTOID-57500"></A>The <EMCLASS="emphasis">switch</EM> statement is used toprocess commands depending on the value of a variable.When you need to handle more than three choices, <EMCLASS="emphasis">switch</EM>is a useful alternative to an <EMCLASS="emphasis">if</EM>-<EMCLASS="emphasis">then</EM>-<EMCLASS="emphasis">else</EM> statement.</P><PCLASS="para">If the <CODECLASS="replaceable"><I>string</I></CODE> variable matches <CODECLASS="replaceable"><I>pattern1</I></CODE>,the first set of <CODECLASS="replaceable"><I>commands</I></CODE> is executed; if <CODECLASS="replaceable"><I>string</I></CODE> matches <CODECLASS="replaceable"><I>pattern2</I></CODE>, the second set of <CODECLASS="replaceable"><I>commands</I></CODE> is executed;and so on. If no patterns match, execute <CODECLASS="replaceable"><I>commands</I></CODE> under the<CODECLASS="literal">default:</CODE> case.<CODECLASS="replaceable"><I>string</I></CODE> can be specified using<SPANCLASS="link">command substitution (<ACLASS="linkend"HREF="ch09_16.htm"TITLE="Command Substitution ">9.16</A>)</SPAN>,<SPANCLASS="link">variable substitution (<ACLASS="linkend"HREF="ch06_08.htm"TITLE="Shell Variables ">6.8</A>)</SPAN>,or<SPANCLASS="link">filename expansion (<ACLASS="linkend"HREF="ch01_16.htm"TITLE="Wildcards ">1.16</A>)</SPAN>.Patterns can be specified using the pattern-matching symbols <CODECLASS="literal">*</CODE>, <CODECLASS="literal">?</CODE>, and<CODECLASS="literal">[]</CODE>. <CODECLASS="literal">breaksw</CODE> is used to exit the <CODECLASS="literal">switch</CODE> after <CODECLASS="replaceable"><I>commands</I></CODE> are executed. If <CODECLASS="literal">breaksw</CODE> is omitted (which is rarely done), the <CODECLASS="literal">switch</CODE> continues to execute another set of <CODECLASS="replaceable"><I>commands</I></CODE> untilit reaches a <CODECLASS="literal">breaksw</CODE> or <CODECLASS="literal">endsw</CODE>.</P><PCLASS="para">Below is the general syntax of <EMCLASS="emphasis">switch</EM>, side by side with an examplethat processes the first command-line argument.</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">switch (<CODECLASS="replaceable"><I>string</I></CODE>)   switch ($argv[1])  case <CODECLASS="replaceable"><I>pattern1</I></CODE>:     case -[nN]:      <CODECLASS="replaceable"><I>commands</I></CODE>          nroff $file | lp      breaksw                              breaksw  case <CODECLASS="replaceable"><I>pattern2</I></CODE>:     case -[Pp]:      <CODECLASS="replaceable"><I>commands</I></CODE>          pr $file | lp      breaksw                              breaksw  case <CODECLASS="replaceable"><I>pattern3</I></CODE>:     case -[Mm]:      <CODECLASS="replaceable"><I>commands</I></CODE>          more $file      breaksw                              breaksw      .                              case -[Ss]:      .                                 sort $file      .                                    breaksw  default:                                    default:      <CODECLASS="replaceable"><I>commands</I></CODE>                   echo &quot;Error-no such option&quot;                                           exit 1      breaksw                                    breakswendsw                                endsw</PRE></BLOCKQUOTE></P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">DG</SPAN> <SPANCLASS="bibliomisc">from O'Reilly &amp; Associates' <CITECLASS="citetitle">UNIX in a Nutshell (SVR4/Solaris)</CITE></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="ch47_05.htm"TITLE="47.5 Using C Shell Arrays "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 47.5 Using C Shell Arrays "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="PART"HREF="part09.htm"TITLE="IX. Miscellaneous "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: IX. Miscellaneous "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">47.5 Using C Shell Arrays </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">IX. Miscellaneous </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 &amp; 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 + -