about_For

TOPIC
	about_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.

 
	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