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, 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, PowerShell reruns the <statement list> section. For
more information about how booleans are evaluated, see
about_Booleans.
The <statement list> section of the statement contains one or more commands
that are run each time the loop is entered or repeated. The <statement list>
can contain any valid PowerShell statements, including the break and
continue keywords.
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
is equal to 0, 1, and 2. Each time through the loop, $val is incremented by 1
using the ++ unary increment operator. The last time through the loop $val
is set to 3, the condition statement evaluates to false, and the loop exits.
To conveniently write this command at the PowerShell command prompt, you can enter it in the following way:
while($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.