'\" '\" Copyright (c) 1993 The Regents of the University of California. '\" Copyright (c) 1994-1996 Sun Microsystems, Inc. '\" '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" '\" RCS: @(#) $Id: if.n,v 1.2 2001/09/14 01:42:22 zlaski Exp $ '\" .so man.macros .TH if n "" Tcl "Tcl Built-In Commands" .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME if \- Execute scripts conditionally .SH SYNOPSIS \fBif \fIexpr1 \fR?\fBthen\fR? \fIbody1 \fBelseif \fIexpr2 \fR?\fBthen\fR? \fIbody2\fR \fBelseif\fR ... ?\fBelse\fR? ?\fIbodyN\fR? .BE .SH DESCRIPTION .PP The \fIif\fR command evaluates \fIexpr1\fR as an expression (in the same way that \fBexpr\fR evaluates its argument). The value of the expression must be a boolean (a numeric value, where 0 is false and anything is true, or a string value such as \fBtrue\fR or \fByes\fR for true and \fBfalse\fR or \fBno\fR for false); if it is true then \fIbody1\fR is executed by passing it to the Tcl interpreter. Otherwise \fIexpr2\fR is evaluated as an expression and if it is true then \fBbody2\fR is executed, and so on. If none of the expressions evaluates to true then \fIbodyN\fR is executed. The \fBthen\fR and \fBelse\fR arguments are optional ``noise words'' to make the command easier to read. There may be any number of \fBelseif\fR clauses, including zero. \fIBodyN\fR may also be omitted as long as \fBelse\fR is omitted too. The return value from the command is the result of the body script that was executed, or an empty string if none of the expressions was non-zero and there was no \fIbodyN\fR. .SH KEYWORDS boolean, conditional, else, false, if, true