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about_While

Updated: August 9, 2012

Applies To: Windows PowerShell 2.0, Windows PowerShell 3.0

TOPIC
    about_While

SHORT DESCRIPTION
    Describes a language statement that you can use to run a command block 
    based on the results of a conditional test.


LONG DESCRIPTION
    The While statement (also known as a While loop) is a language construct
    for creating a loop that runs commands in a command block as long as a
    conditional test evaluates to true. The While statement is easier to 
    construct than a For statement because its syntax is less complicated.
    In addition, it is more flexible than the Foreach statement because you
    specify a conditional test in the While statement to control how many times
    the loop runs.
 

    The following shows the While statement syntax:

        while (<condition>){<statement list>}


    When you run a While statement, Windows PowerShell evaluates 
    the <condition> section of the statement before entering the 
    <statement list> section. The condition portion of the statement resolves
    to either true or false. As long as the condition remains true, Windows 
    PowerShell reruns the <statement list> section.


    The <statement list> section of the statement contains one or more commands
    that are run each time the loop is entered or repeated.


    For example, the following While statement displays the numbers 1 
    through 3 if the $val variable has not been created or if the $val variable
    has been created and initialized to 0.

        while($val -ne 3)
        {
            $val++
            Write-Host $val
        }


    In this example, the condition ($val is not equal to 3) is true while 
    $val = 0, 1, 2. Each time through the loop, $val is incremented by 1 
    using the ++ unary increment operator ($val++). The last time through 
    the loop, $val = 3. When $val equals 3, the condition statement 
    evaluates to false, and the loop exits.
 

    To conveniently write this command at the Windows PowerShell command 
    prompt, you can enter it in the following way:

        while($val -ne 3){$val++; Write-Host $val} 


    Notice that the semicolon separates the first command that adds 1 to 
    $val from the second command that writes the value of $val to the 
    console.
 

SEE ALSO
    about_Comparison_Operators
    about_Do
    about_Foreach
    about_For
    about_Language_Keywords

    



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