36 lines
2.1 KiB
HTML
36 lines
2.1 KiB
HTML
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<HTML><HEAD><TITLE>Built-In Commands - if manual page</TITLE></HEAD><BODY>
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<H3><A NAME="M2">NAME</A></H3>
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if - Execute scripts conditionally
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<H3><A NAME="M3">SYNOPSIS</A></H3>
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<B>if </B><I>expr1 </I>?<B>then</B>? <I>body1 </I><B>elseif </B><I>expr2 </I>?<B>then</B>? <I>body2</I> <B>elseif</B> ... ?<B>else</B>? ?<I>bodyN</I>?<BR>
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<H3><A NAME="M4">DESCRIPTION</A></H3>
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The <I>if</I> command evaluates <I>expr1</I> as an expression (in the
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same way that <B><A HREF="../TkCmd/expr.htm">expr</A></B> evaluates its argument). The value of the
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expression must be a boolean
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(a numeric value, where 0 is false and
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anything is true, or a string value such as <B>true</B> or <B>yes</B>
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for true and <B>false</B> or <B>no</B> for false);
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if it is true then <I>body1</I> is executed by passing it to the
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Tcl interpreter.
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Otherwise <I>expr2</I> is evaluated as an expression and if it is true
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then <B>body2</B> is executed, and so on.
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If none of the expressions evaluates to true then <I>bodyN</I> is
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executed.
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The <B>then</B> and <B>else</B> arguments are optional
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``noise words'' to make the command easier to read.
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There may be any number of <B>elseif</B> clauses, including zero.
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<I>BodyN</I> may also be omitted as long as <B>else</B> is omitted too.
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The return value from the command is the result of the body script
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that was executed, or an empty string
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if none of the expressions was non-zero and there was no <I>bodyN</I>.
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<H3><A NAME="M5">SEE ALSO</A></H3>
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<B><A HREF="../TkCmd/expr.htm">expr</A></B>, <B><A HREF="../TkCmd/for.htm">for</A></B>, <B><A HREF="../TkCmd/foreach.htm">foreach</A></B>
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<H3><A NAME="M6">KEYWORDS</A></H3>
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<A href="../Keywords/B.htm#boolean">boolean</A>, <A href="../Keywords/C.htm#conditional">conditional</A>, <A href="../Keywords/E.htm#else">else</A>, <A href="../Keywords/F.htm#false">false</A>, <A href="../Keywords/I.htm#if">if</A>, <A href="../Keywords/T.htm#true">true</A>
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<HR><PRE>
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<A HREF="../copyright.htm">Copyright</A> © 1993 The Regents of the University of California.
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<A HREF="../copyright.htm">Copyright</A> © 1994-1996 Sun Microsystems, Inc.
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<A HREF="../copyright.htm">Copyright</A> © 1995-1997 Roger E. Critchlow Jr.</PRE>
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</BODY></HTML>
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