about_do | Easy Powershell 2.0 Reference

SHORT DESCRIPTION
Runs a statement list one or more times, subject to a While or Until
condition.

LONG DESCRIPTION
    The Do keyword works with the While keyword or the Until keyword to run
    the statements in a script block, subject to a condition. Unlike the
    related While loop, the script block in a Do loop always runs at least
    once.

    A Do-While loop is a variety of the While loop. In a Do-While loop, the
    condition is evaluated after the script block has run. As in a While loop,
    the script block is repeated as long as the condition evaluates to true.

    Like a Do-While loop, a Do-Until loop always runs at least once before
    the condition is evaluated. However, the script block runs only while
    the condition is false.

The Continue and Break flow control keywords can be used in a Do-While
loop or in a Do-Until loop.

Syntax
The following shows the syntax of the Do-While statement:

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

The following shows the syntax of the Do-Until statement:

do {<statement list>} until (<condition>)

The statment list contains one or more statements that run each time
the loop is entered or repeated.

The condition portion of the statement resolves to true or false.

Example
The following example of a Do statement counts the items in an
array until it reaches an item with a value of 0.

         C:\PS> $x = 1,2,78,0
         C:\PS> do { $count++; $a++; } while ($x[$a] -ne 0)
         C:\PS> $count
         3

     The following example uses the Until keyword. Notice that
     the not equal to operator (-ne) is replaced by the
     equal to operator (-eq).

         C:\PS> $x = 1,2,78,0
         C:\PS> do { $count++; $a++; } until ($x[$a] -eq 0)
         C:\PS> $count
         3

The following example writes all the values of an array, skipping any
value that is less than zero.

         do
         {
             if ($x[$a] -lt 0) { continue }
             Write-Host $x[$a]
         }
         while (++$a -lt 10)