How to Check if a String Is Not NULL or EMPTY in PowerShell

1. Use a Conditional Statement to Check if a String Variable Is Not Null or Empty in PowerShell
2. Use the IsNullorEmpty Method to Check if a String Variable Is Not Null or Empty in PowerShell
3. Use the IsNullOrWhiteSpace Method to Check if a String Variable Is Not Null or Empty in PowerShell
4. Use the $null Variable to Check if a String Variable Is Not Null or Empty in PowerShell

A string is the sequence of characters used to represent texts. You can define the string using single or double quotes in PowerShell.

While working with string variables in PowerShell, sometimes you might need to check whether a string variable is null or empty. This tutorial will introduce different methods to check if a string variable is not null or empty in PowerShell.

Use a Conditional Statement to Check if a String Variable Is Not Null or Empty in PowerShell

We have created a string variable, $string.

$string = "Hello World"

The following example checks if a $string variable is null or not in PowerShell. It returns the first statement if the variable is not null or empty and the second statement if the variable is null or empty.

if ($string) {
    Write-Host "The variable is not null."
}
else {
    Write-Host "The variable is null."
}

Output:

The variable is not null.

Let’s assign an empty string value to a variable and check again. If a variable is not assigned, it also has a null value.

$string = ""
if ($string) {
    Write-Host "The variable is not null."
}
else {
    Write-Host "The variable is null."
}

Output:

The variable is null.

White space characters are not considered null string values.

Use the IsNullorEmpty Method to Check if a String Variable Is Not Null or Empty in PowerShell

You can use the .NET class System.String to check if a string variable is null or empty in PowerShell. The IsNullorEmpty() method indicates whether the specified string is empty or null.

It returns True if the string is empty and False if it is not empty.

[string]::IsNullOrEmpty($new)

Output:

True

Now, let’s assign a string value to a variable.

$new = "asdf"
[string]::IsNullOrEmpty($new)

Output:

False

Use the IsNullOrWhiteSpace Method to Check if a String Variable Is Not Null or Empty in PowerShell

You can also use the IsNullOrWhiteSpace method to check if a string variable is not null or empty in PowerShell. This method only works from PowerShell 3.0.

It returns True if the variable is null or empty or contains white space characters. If not, it prints False in the output.

[string]::IsNullOrWhiteSpace($str)

Output:

True

Assign a string value to a variable.

$str = "Have a nice day."
[string]::IsNullOrWhiteSpace($str)

Output:

False

Use the $null Variable to Check if a String Variable Is Not Null or Empty in PowerShell

$null is one of the automatic variables in PowerShell, which represents NULL. You can use the -eq parameter to check if a string variable equals $null.

It returns True if the variable is equal to $null and False if the variable is not equal to $null.

$str -eq $null

Output:

False

We can use any of the methods above and easily determine whether a string variable is not null or empty in PowerShell.