PowerShell Logo Small

about_If



This is the built-in help made by Microsoft for the document 'about_If', in PowerShell version 2 - as retrieved from Windows version 'Microsoft® Windows Vista™ Ultimate ' PowerShell help files on 2016-06-24.

For PowerShell version 3 and up, where you have Update-Help, this command was run just before creating the web pages from the help files.

Search powershellhelp.space

TOPIC
about_If

SHORT DESCRIPTION
Describes a language command you can use to run statement lists based
on the results of one or more conditional tests.


LONG DESCRIPTION
You can use the If statement to run code blocks if a specified
conditional test evaluates to true. You can also specify one or more
additional conditional tests to run if all the prior tests evaluate to
false. Finally, you can specify an additional code block that is run if
no other prior conditional test evaluates to true.


Syntax
The following example shows the If statement syntax:


if (<test1>)
{<statement list 1>}
[elseif (<test2>)
{<statement list 2>}]
[else
{<statement list 3>}]


When you run an If statement, Windows PowerShell evaluates the
<test1> conditional expression as true or false. If <test1> is true,
<statement list 1> runs, and Windows PowerShell exits the If statement.
If <test1> is false, Windows PowerShell evaluates the condition specified
by the <test2> conditional statement.


If <test2> is true, <statement list 2> runs, and Windows PowerShell
exits the If statement. If both <test1> and <test2> evaluate to false,
the <statement list 3> code block runs, and Windows PowerShell exits
the If statement.


You can use multiple Elseif statements to chain a series of conditional
tests so that each test is run only if all the previous tests are
false. If you need to create an If statement that contains many
Elseif statements, consider using a Switch statement instead.


Examples
The simplest If statement contains a single command
and does not contain any Elseif statements or any Else statements. The
following example shows the simplest form of the If statement:


if ($a -gt 2)
{
Write-Host "The value $a is greater than 2."
}


In this example, if the $a variable is greater than 2, the condition
evaluates to true, and the statement list runs. However, if $a is less
than or equal to 2 or is not an existing variable, the If statement does
not display a message. By adding an Else statement, a message is displayed
when $a is less than or equal to 2, as the next example shows:


if ($a -gt 2)
{
Write-Host "The value $a is greater than 2."
}
else
{
Write-Host "The value $a is less than or equal to 2, is not
created or is not initialized."
}


To further refine this example, you can use the Elseif statement to
display a message when the value of $a is equal to 2, as the next
example shows:


if ($a -gt 2)
{
Write-Host "The value $a is greater than 2."
}
elseif ($a -eq 2)
{
Write-Host "The value $a is equal to 2."
}
else
{
Write-Host "The value $a is less than 2 or was not created
or initialized."
}
about_Comparison_Operators
about_Switch