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Learn how to use the PowerShell Trim method

With the Trim method in your PowerShell toolbox, you can write scripts to remove unwanted characters from strings without using regular expressions. Get started with this tutorial.

All the work you do with PowerShell that deals with input or imported data depends on the quality of that data. When working with scripts that ingest data, you can use techniques such as parameter validation, regular expressions and even manual review. But sometimes you'll need to clean the data yourself.

In PowerShell, one tool for working with strings is the Trim() method, which removes unwanted characters from the start and ends of strings. In some cases, using Trim() even eliminates the need to write regular expressions, simplifying your code and creating a better experience for others who use your scripts.

Although all the examples in this tutorial are executed in PowerShell 7, they'll work the same in Windows PowerShell unless stated otherwise.

Call the Trim() method without parameters

In PowerShell, strings are considered a primitive type, meaning they're built into the language. Like any variable in PowerShell, strings have methods and properties.

Properties are static values associated with a variable, whereas methods perform a specific action when called. Unlike properties, methods are called with parentheses at the end, which sometimes contain parameters.

You can call the Trim() method without any parameters to remove spaces at the start and end of a string. For example, executing the Trim() method on a string variable $str with the value ' string ' outputs 'string', as shown in Figure 1.

Screenshot of PowerShell script to initialize and display a string variable, then trim spaces and display output length.
Figure 1. The output is two characters shorter after running Trim() without parameters to remove spaces.

You can test this yourself by running the following code, which shows that the output string is two characters shorter. Because it is difficult to display spaces in console output, this example uses the Length property, which returns the number of characters in a string.

$str = ' string '
Write-Host "Length: $($str.Length)"
Write-Host "Trimmed Length: $($str.Trim().Length)"

Importantly, the Trim() method does not update the original variable; it simply returns the modified string to the console. To update the $str variable with the trimmed version of the string, run the command $str = $str.Trim(). As with all variable assignments, there is no output, but you can validate the results by outputting $str.

Call the Trim() method with a single parameter

You can also remove characters other than spaces with Trim() by using parameters. For example, to read data containing strings wrapped in single quotes, remove the quotes by including a single quote as a parameter using the following code.

$str = "' string '"
Write-Host "Length: $($str.Length)"
Write-Host "Trimmed Length: $($str.Trim("'").Length)"

Here, executing Trim() doesn't remove spaces from the string because Trim() only removes the characters passed in the parameter, which didn't include spaces.

Screenshot of PowerShell script to initialize and display a string variable, then trim single quotes and display output length.
Figure 2. Single quotes are removed from the string after running the command.

Call the Trim() method with multiple parameters

You can also pass an array of characters to the Trim() method to remove all instances of any of those characters from the start and end of a string. The method keeps removing characters until it encounters a character not included in the parameters.

Continuing with the previous example, the following code removes both single quotes and spaces from the string by including both characters in the parameter.

$str = "' string '"
Write-Host "Length: $($str.Length)"
$str.Trim("' ")
Write-Host "Trimmed Length: $($str.Trim("' ").Length)"

As mentioned above, the Trim() parameters accept characters, but this code passes Trim() a string, as shown in Figure 3.

Screenshot of PowerShell script to initialize and display a string variable, then trim single quotes and spaces and display output length.
Figure 3. Single quotes and spaces are both removed from the string after including both characters in the parameter.

Here, Trim() converts the string into a character array. In PowerShell, this is simply a matter of typecasting using [char[]]'string'.

Screenshot of PowerShell script to convert the string 'string' into an array of characters using typecasting.
Figure 4. Strings can be converted to character arrays in PowerShell using typecasting.

To see the parameters for Trim(), you can call the method without any parentheses using the command 'str'.Trim, as shown in Figure 5.

Screenshot of PowerShell script that calls the Trim method without parentheses to show its parameters.
Figure 5. Calling the Trim() method without parentheses shows the parameters.

Remove leading and trailing characters with TrimStart() and TrimEnd()

The methods TrimStart() and TrimEnd() are handy for use cases that involve trimming only one end of a string, rather than both.

To see how the two methods work, run the following code.

$str = "'string'"

As shown in Figure 6, TrimStart() removes the single quote from the beginning, and TrimEnd() removes it from the end.

Screenshot of PowerShell script to initialize and display a string variable, then remove single quotes using TrimStart and TrimEnd.
Figure 6. TrimStart() removes the leading single quote, whereas TrimEnd()removes the trailing single quote.

Practical use cases for the Trim() method

Now that you know how to use the variations of Trim(), take a look at a couple of practical examples.

Writing user creation scripts

A common use case for Trim() involves dealing with input, especially user input. For example, trimming names is useful when writing user creation scripts that accept user input, either directly or from a spreadsheet.

This is especially important if you're passing first and last names to generate usernames. As an example, say HR has sent you a spreadsheet with employees' first and last names, among other data, and your company uses the format firstname.lastname for usernames. Figure 7 shows the imported data that HR provided in the spreadsheet.

Screenshot from PowerShell of sample data for a user with the first name Anthony and last name Howell.
Figure 7. As imported, the last name field contains an extra space before the user's name.

In the imported data, the last name has a space at the beginning -- a common problem with copying and pasting. Attempting to create the sAMAccountName or userPrincipalName in Active Directory using the original data will result in the output shown in Figure 8.

Screenshot from PowerShell joining the user's first and last name with a period, showing the extra space before the user's last name.
Figure 8. Because there is a space before the user's last name in the imported data, that space will also appear when creating a username.

Now imagine doing that on a bulk import of a large group of employees from an acquisition, then explaining to executives what went wrong! A simple use of Trim() would have prevented the error.

Working with paths

Another common use for Trim() is when working with paths, especially as parameters. In such cases, using Trim() can eliminate the need to write regular expressions to accept paths with or without a separator at the end.

For example, the following two paths are both valid (assuming the folder in question exists):

  • C:\tmp\folder
  • C:\tmp\folder\

Likewise, the following web paths are both valid:


But what if you want to join multiple paths? You could join the paths with a slash and hope that a potential double slash doesn't break things, or you could check whether the path ends with a slash and only add one if it doesn't.

Alternatively, you could simply use Trim() to remove any trailing slashes, then add any necessary slash before constructing the new directory path. In the following example, the function takes a base path as a parameter and then adds a subfolder.

Function Do-Things {
    param (
    New-Item -LiteralPath "$($Path.TrimEnd('/\'))
ew\folder" -ItemType Directory

With this code, it doesn't matter whether the $Path parameter has a trailing slash because the function handles both cases. If the original path contains a slash, Trim() removes it; if it doesn't, it won't matter.

If you are working on Windows, multiple directory separators don't invalidate the path, as shown in Figure 9.

Screenshot from PowerShell showing that Test-Path returns True regardless of how many directory separators are used.
Figure 9. In Windows environments, using multiple directory separators doesn't invalidate a path.

However, using multiple separators on a web path is not valid.

Next Steps

Connect data with PowerShell's Join-Object module

How to use regex in PowerShell

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