Conditions

Comparing two variables

In PowerShell we can compare variables equality and check is a value in an array etc. Comparisons will return True or False.
Comparison Operator -eq means equality.

$a, $b = "Jack", "Jake"
$a -eq $b

Comparison Operator -ne means not equality.

$a, $b = "Jack", "Jake"
$a -ne $b

The full list of Comparison Operators is below.

Flow Control

In PowerShell scripts we can control the flow of the script. Sometimes we do something depending of a condition or conditions. And sometimes we will check if a condition is true or false. The If-clause is classic legendary way to do it. Let's Go!

$a,$b = 'Jack', 'unknown'
if ($a -eq 'Jakke')  
   {Write-Host "Terve Jakke"}  
else 
    {Write-Host "Hello", $b}  

Let's try with array, is a person in the group.

$a = 'Jack'
$myfriends = 'Al', 'Ben', 'Jack', 'Zake'
if ($myfriends -contains $a)
  {Write-Host $a, "is my friend"} 
else 
  {Write-Host $a, "is not in my friend list"}

Example with IP Address

#get all ip data from ipconfig application
$myip = ipconfig.exe
# in this context id 13 is my IP address
$myipa = $myip[13]
if($myipa -like '*192.168*'){Write-host "Internal Network"} else{"Not Internal IP"}

Example with comparing numbers

In the example, we compare is a given number less that set limit, and is it in array.

#ask an odd number from user
$input = Read-Host "Give one odd number below ten"
$a = [int]$input
if ($a -lt 10)
{
  $odds = 1,3,5,7,9
  if ($odds -contains $a)
    {$output = "You gave an odd number " + $a}
  else
    {$output = "Given number " + $a + " is not valid"}
}
else {$output = "Given number " + $a + " is too big!" } 
#finally
Write-Host $output

Comparison Operators

PowerShell contains a number of comparison operators, which are used to compare values and to find values that match certain patterns. Note: PowerShell doesn't use the traditional comparison operators that you may know from other programming languages. In particular, the "=" operator is purely an assignment operator in PowerShell, while ">" and "<" operators are used for redirection.

Here is a list of comparison operators in PowerShell.

operator	meaning
-eq	Equal to.
-ne	Not equal to.
-gt	Greater than.
-ge	Greater than or equal to.
-lt	Less than.
-le	Less than or equal to.
-Like	Match using the * wildcard character.
-NotLike	Does not match using the * wildcard character.
-Match	Matches the specified regular expression.
-NotMatch	Does not match the specified regular expression.
-Contains	Determines if a collection contains a specified value.
-NotContains	Determines if a collection does not contain a specific value.
-In	Determines if a specified value is in a collection.
-NotIn	Determines if a specified value is not in a collection.
-Replace	Replaces the specified value.

In the following example is tested contains the array of names certain names.

$names = 'Arska', 'Ben', 'Calle', 'David'
$names -contains 'Ben' 
$names -contains 'BEN'
$names -contains 'Eric'

Logical Operators

You can se logical operators (-and, -or, -xor, -not, !) to connect conditional statements into a single complex conditional. For example, you can use a logical -and operator to create an object filter with two different conditions. Or you can use a logical -or operator to test is either one of conditions true.

In the following example we find out is IP-address Internal or not.

#IPs to test are they internal or not
$ips = '192.168.1.1', '10.10.1.1', '204.203.1.1'
foreach ($ip in $ips) {
  if ($ip -like '192.168*' -Or $ip -like '10.10*')
      {Write-host "$ip is Internal Network"} 
  else{"$ip is not Internal IP"}
}