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Full Discussion: what is $1
Top Forums UNIX for Dummies Questions & Answers what is $1 Post 302259666 by glev2005 on Tuesday 18th of November 2008 05:06:14 PM
Old 11-18-2008
what is $1

I see $1 in many scripts, can someone explain in the most simple terms useful, what does it mean/do please? It is never defined before, I read something like it's a conditional variable, help me out.. I want to be able to use it since it obviously is useful
 
if(n)							       Tcl Built-In Commands							     if(n)

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NAME
if - Execute scripts conditionally SYNOPSIS
if expr1 ?then? body1 elseif expr2 ?then? body2 elseif ... ?else? ?bodyN? _________________________________________________________________ DESCRIPTION
The if command evaluates expr1 as an expression (in the same way that expr 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 true or yes for true and false or no for false); if it is true then body1 is executed by passing it to the Tcl interpreter. Otherwise expr2 is evaluated as an expression and if it is true then body2 is executed, and so on. If none of the expressions evaluates to true then bodyN is executed. The then and else arguments are optional "noise words" to make the command easier to read. There may be any number of elseif clauses, including zero. BodyN may also be omitted as long as else 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 bodyN. EXAMPLES
A simple conditional: if {$vbl == 1} { puts "vbl is one" } With an else-clause: if {$vbl == 1} { puts "vbl is one" } else { puts "vbl is not one" } With an elseif-clause too: if {$vbl == 1} { puts "vbl is one" } elseif {$vbl == 2} { puts "vbl is two" } else { puts "vbl is not one or two" } Remember, expressions can be multi-line, but in that case it can be a good idea to use the optional then keyword for clarity: if { $vbl == 1 || $vbl == 2 || $vbl == 3 } then { puts "vbl is one, two or three" } SEE ALSO
expr(n), for(n), foreach(n) KEYWORDS
boolean, conditional, else, false, if, true Tcl if(n)
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