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about_For

For

 

SHORT DESCRIPTION

    Describes a language command you can use to run statements based on a 
    conditional test. 
 
 

LONG DESCRIPTION

    The For statement (also known as a For loop) is a language construct  
    you can use to create a loop that runs commands in a command block while a  
    specified condition evaluates to true.  
 
 
    A typical use of the For loop is to iterate an array of values and to  
    operate on a subset of these values. In most cases, if you want to  
    iterate all the values in an array, consider using a Foreach statement. 
 
 
  Syntax 
      The following shows the For statement syntax. 
       
   
          for (<init>; <condition>; <repeat>)  
          {<statement list>} 
 
       
      The <init> placeholder represents one or more commands, separated by  
      commas, that are run before the loop begins. You typically use the  
      <init> portion of the statement to create and initialize a variable with 
      a starting value. Note that the comma syntax doesn't work with 
      assignment statements, such as the following example: 
 
          $ofs=",";$rs = "rs"; $cs = "cs"; for ($r = $rs, $c = $cs; $true;)  
          { "r is '$r' and c is '$c'"; break } 
 
  
      This variable will then be the basis for the condition to be tested in  
      the next portion of the For statement. 
 
         
      The <condition> placeholder represents the portion of the For statement  
      that resolves to a true or false Boolean value. Windows PowerShell  
      evaluates the condition each time the For loop runs. If the statement is  
      true, the commands in the command block run, and the statement is  
      evaluated again. If the condition is still true, the commands in the  
      statement list run again. The loop is repeated until the condition  
      becomes false. 
 
      
      The <repeat> placeholder represents one or more commands, separated by  
      commas, that are executed each time the loop repeats. Typically, this  
      is used to modify a variable that is tested inside the <condition> part 
      of the statement. 
 
         
      The <statement list> placeholder represents a set of one or more commands 
      that are run each time the loop is entered or repeated. The contents of 
      the statement list are surrounded by braces. 
 
 
  Examples 
      At a minimum, a For statement requires the parenthesis surrounding the  
      <init>, <condition>, and <repeat> part of the statement and a command  
      surrounded by braces in the <statement list> part of the statement.  
 
 
      Note that the upcoming examples intentionally show code outside the  
      For statement. In later examples, code is integrated into the for  
      statement. 
 
 
      For example, the following For statement continually displays the  
      value of the $i variable until you manually break out of the command by  
      pressing CTRL+C.  
 
 
          $i = 1 
          for (;;){Write-Host $i} 
 
 
      You can add additional commands to the statement list so that  
      the value of $i is incremented by 1 each time the loop is run, as the  
      following example shows. 
 
 
          for (;;){$i++; Write-Host $i} 
 
 
      Until you break out of the command by pressing CTRL+C, this statement  
      will continually display the value of the $i variable as it is  
      incremented by 1 each time the loop is run. 
 
 
      Rather than change the value of the variable in the statement list  
      part of the For statement, you can use the <repeat> portion of the For  
      statement instead, as follows.  
 
 
          $i=1 
          for (;;$i++){Write-Host $i} 
 
 
      This statement will still repeat indefinitely until you break out of the  
      command by pressing CTRL+C. 
 
 
      By setting a condition (using the <condition> portion of the For 
      statement), you can end the For loop when the condition evaluates to  
      false. In the following example, the For loop runs while the value of  
      $i is less than or equal to 10. 
  
 
          $i=1 
          for(;$i -le 10;$i++){Write-Host $i} 
 
 
      Instead of creating and initializing the variable outside the For  
      statement, you can perform this task inside the For loop by using  
      the <init> portion of the For statement. 
 
 
          for($i=1; $i -le 10; $i++){Write-Host $i} 
 
 
      You can use carriage returns instead of semicolons to delimit the  
      <init>, <condition>, and <repeat> portions of the For statement. The 
      following example shows the For statement syntax in this alternative  
      form. 
 
         
            for (<init> 
          <condition> 
          <repeat>){ 
          <statement list> 
          } 
 
       
      This alternative form of the For statement works in Windows PowerShell  
      script files and at the Windows PowerShell command prompt. However, it 
      is easier to use the For statement syntax with semicolons when you enter 
      interactive commands at the command prompt.  
 
         
      The For loop is more flexible than the Foreach loop because it allows  
      you to increment values in an array or collection by using patterns. In 
      the following example, the $i variable is incremented by 2 in the  
      <repeat> portion of the for statement. 
 
 
          for ($i = 0; $i -ile 20; $i += 2) {Write-Host $i} 
 
 

SEE ALSO

about_Comparison_Operators
about_Foreach