| 1 | '\" |
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| 2 | '\" Copyright (c) 1993 The Regents of the University of California. |
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| 3 | '\" Copyright (c) 1994-1996 Sun Microsystems, Inc. |
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| 4 | '\" |
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| 5 | '\" See the file "license.terms" for information on usage and redistribution |
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| 6 | '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. |
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| 7 | '\" |
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| 8 | '\" RCS: @(#) $Id: if.n,v 1.9 2007/12/13 15:22:32 dgp Exp $ |
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| 9 | '\" |
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| 10 | .so man.macros |
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| 11 | .TH if n "" Tcl "Tcl Built-In Commands" |
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| 12 | .BS |
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| 13 | '\" Note: do not modify the .SH NAME line immediately below! |
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| 14 | .SH NAME |
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| 15 | if \- Execute scripts conditionally |
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| 16 | .SH SYNOPSIS |
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| 17 | \fBif \fIexpr1 \fR?\fBthen\fR? \fIbody1 \fBelseif \fIexpr2 \fR?\fBthen\fR? \fIbody2\fR \fBelseif\fR ... ?\fBelse\fR? ?\fIbodyN\fR? |
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| 18 | .BE |
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| 19 | |
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| 20 | .SH DESCRIPTION |
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| 21 | .PP |
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| 22 | The \fIif\fR command evaluates \fIexpr1\fR as an expression (in the |
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| 23 | same way that \fBexpr\fR evaluates its argument). The value of the |
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| 24 | expression must be a boolean |
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| 25 | (a numeric value, where 0 is false and |
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| 26 | anything is true, or a string value such as \fBtrue\fR or \fByes\fR |
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| 27 | for true and \fBfalse\fR or \fBno\fR for false); |
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| 28 | if it is true then \fIbody1\fR is executed by passing it to the |
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| 29 | Tcl interpreter. |
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| 30 | Otherwise \fIexpr2\fR is evaluated as an expression and if it is true |
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| 31 | then \fBbody2\fR is executed, and so on. |
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| 32 | If none of the expressions evaluates to true then \fIbodyN\fR is |
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| 33 | executed. |
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| 34 | The \fBthen\fR and \fBelse\fR arguments are optional |
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| 35 | .QW "noise words" |
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| 36 | to make the command easier to read. |
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| 37 | There may be any number of \fBelseif\fR clauses, including zero. |
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| 38 | \fIBodyN\fR may also be omitted as long as \fBelse\fR is omitted too. |
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| 39 | The return value from the command is the result of the body script |
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| 40 | that was executed, or an empty string |
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| 41 | if none of the expressions was non-zero and there was no \fIbodyN\fR. |
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| 42 | .SH EXAMPLES |
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| 43 | A simple conditional: |
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| 44 | .CS |
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| 45 | \fBif\fR {$vbl == 1} { puts "vbl is one" } |
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| 46 | .CE |
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| 47 | .PP |
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| 48 | With an \fBelse\fR-clause: |
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| 49 | .CS |
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| 50 | \fBif\fR {$vbl == 1} { |
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| 51 | puts "vbl is one" |
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| 52 | } \fBelse\fR { |
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| 53 | puts "vbl is not one" |
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| 54 | } |
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| 55 | .CE |
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| 56 | .PP |
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| 57 | With an \fBelseif\fR-clause too: |
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| 58 | .CS |
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| 59 | \fBif\fR {$vbl == 1} { |
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| 60 | puts "vbl is one" |
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| 61 | } \fBelseif\fR {$vbl == 2} { |
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| 62 | puts "vbl is two" |
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| 63 | } \fBelse\fR { |
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| 64 | puts "vbl is not one or two" |
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| 65 | } |
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| 66 | .CE |
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| 67 | .PP |
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| 68 | Remember, expressions can be multi-line, but in that case it can be a |
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| 69 | good idea to use the optional \fBthen\fR keyword for clarity: |
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| 70 | .CS |
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| 71 | \fBif\fR { |
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| 72 | $vbl == 1 || $vbl == 2 || $vbl == 3 |
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| 73 | } \fBthen\fR { |
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| 74 | puts "vbl is one, two or three" |
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| 75 | } |
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| 76 | .CE |
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| 77 | |
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| 78 | .SH "SEE ALSO" |
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| 79 | expr(n), for(n), foreach(n) |
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| 80 | |
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| 81 | .SH KEYWORDS |
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| 82 | boolean, conditional, else, false, if, true |
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