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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 47] 47.3 Conditional Statements with if </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="1998-08-04T21:55:58Z"><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_02.htm"TITLE="47.2 C Shell Programming Considered Harmful "><LINKREL="next"HREF="ch47_04.htm"TITLE="47.4 C Shell Variable Operators and Expressions "></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_02.htm"TITLE="47.2 C Shell Programming Considered Harmful "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 47.2 C Shell Programming Considered Harmful "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="SECT1"HREF="ch47_04.htm"TITLE="47.4 C Shell Variable Operators and Expressions "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 47.4 C Shell Variable Operators and Expressions "BORDER="0"></A></TD></TR></TABLE>&nbsp;<HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-8018">47.3 Conditional Statements with if </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-56622"></A><ACLASS="indexterm"NAME="AUTOID-56625"></A><ACLASS="indexterm"NAME="AUTOID-56628"></A><ACLASS="indexterm"NAME="AUTOID-56631"></A><EMCLASS="emphasis">.login</EM> and <EMCLASS="emphasis">.cshrc</EM> files&quot; 1070is the use of conditionals (<EMCLASS="emphasis">if</EM> statements). This article explainsthe syntax of <EMCLASS="emphasis">if</EM> statements. Article<ACLASS="xref"HREF="ch47_04.htm"TITLE="C Shell Variable Operators and Expressions ">47.4</A>ofexplains the syntax of the expressions you can test with an <EMCLASS="emphasis">if</EM>.</P><PCLASS="para">The <EMCLASS="emphasis">if</EM> command is used tobegin a conditional statement. The simple format is:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">if (<CODECLASS="replaceable"><I>expr</I></CODE>) <CODECLASS="replaceable"><I>cmd</I></CODE></PRE></BLOCKQUOTE></P><PCLASS="para">There are three other possible formats, shown side-by-side:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">if (<CODECLASS="replaceable"><I>expr</I></CODE>) then   if (<CODECLASS="replaceable"><I>expr</I></CODE>) then   if (<CODECLASS="replaceable"><I>expr</I></CODE>) then   <CODECLASS="replaceable"><I>cmds</I></CODE>      <CODECLASS="replaceable"><I>cmds1</I></CODE>      <CODECLASS="replaceable"><I>cmds1</I></CODE>endif   else   else if (<CODECLASS="replaceable"><I>expr</I></CODE>) then      <CODECLASS="replaceable"><I>cmds2</I></CODE>      <CODECLASS="replaceable"><I>cmds2</I></CODE>   endif   else         <CODECLASS="replaceable"><I>cmds3</I></CODE>      endif</PRE></BLOCKQUOTE></P><PCLASS="para">In the simplest form, execute <CODECLASS="replaceable"><I>cmd</I></CODE> if <CODECLASS="replaceable"><I>expr</I></CODE> is true;otherwise do nothing (redirection still occurs; this is a bug). In the other forms, execute one or more commands.If <CODECLASS="replaceable"><I>expr</I></CODE> is true, continue with the commands after <CODECLASS="literal">then</CODE>;if <CODECLASS="replaceable"><I>expr</I></CODE> is false, branch to the commands after <CODECLASS="literal">else</CODE>(or after the <CODECLASS="literal">else if</CODE> and continue checking).For example, the following <EMCLASS="emphasis">if</EM> clause willtake a default action if no command-line arguments are given:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">if ($#argv == 0) then   echo &quot;No filename given. Sending to Report.&quot;   set outfile = Reportelse   set outfile = $argv[1]endif</PRE></BLOCKQUOTE></P><PCLASS="para">For more examples, see article<ACLASS="xref"HREF="ch47_04.htm"TITLE="C Shell Variable Operators and Expressions ">47.4</A>.</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_02.htm"TITLE="47.2 C Shell Programming Considered Harmful "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 47.2 C Shell Programming Considered Harmful "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="ch47_04.htm"TITLE="47.4 C Shell Variable Operators and Expressions "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 47.4 C Shell Variable Operators and Expressions "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">47.2 C Shell Programming Considered Harmful </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">47.4 C Shell Variable Operators and Expressions </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>
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