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Full Discussion: Loop Counting Question
Top Forums UNIX for Dummies Questions & Answers Loop Counting Question Post 302747149 by phunk on Thursday 20th of December 2012 04:32:49 PM
Old 12-20-2012
Loop Counting Question

I figured this out, but I wanted to pose the question.

I was writing a while loop that required counting the amount of times the job had run, for example.

An example below is what I had:

Code:
variable=0

while :
do
    variable = `expr $variable + 1`
done

That didn't do what I needed it to (allow multiple attempts of input). However the following did:

Code:
variable=0

while :
do
    (( variable = variable + 1 ))
done

I was just curious why the double parenthesis handled that while the expr statement didn't. I'm still learning Smilie
 

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set(n)							       Tcl Built-In Commands							    set(n)

__________________________________________________________________________________________________________________________________________________

NAME
set - Read and write variables SYNOPSIS
set varName ?value? _________________________________________________________________ DESCRIPTION
Returns the value of variable varName. If value is specified, then set the value of varName to value, creating a new variable if one doesn't already exist, and return its value. If varName contains an open parenthesis and ends with a close parenthesis, then it refers to an array element: the characters before the first open parenthesis are the name of the array, and the characters between the parentheses are the index within the array. Otherwise varName refers to a scalar variable. Normally, varName is unqualified (does not include the names of any containing namespaces), and the variable of that name in the current namespace is read or written. If varName includes names- pace qualifiers (in the array name if it refers to an array element), the variable in the specified namespace is read or written. If no procedure is active, then varName refers to a namespace variable (global variable if the current namespace is the global namespace). If a procedure is active, then varName refers to a parameter or local variable of the procedure unless the global command was invoked to declare varName to be global, or unless a variable command was invoked to declare varName to be a namespace variable. SEE ALSO
expr(n), proc(n), trace(n), unset(n) KEYWORDS
read, write, variable Tcl set(n)
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