PowerShell Substring() Example

The Substring() method is very helpful for working with PowerShell strings. In this PowerShell tutorial, I will explain how to use the Substring() method to extract parts of a string in PowerShell with a few real examples.

What is the Substring() Method in PowerShell

The Substring() method is a member of the String class in .NET. It allows you to extract a string portion based on a starting index and an optional length.

Method Overloads

The PowerShell Substring() method has two overloads:

1. Substring(Int32 startIndex): Extracts a substring starting from the specified index to the end of the string.
2. Substring(Int32 startIndex, Int32 length): Extracts a substring starting from the specified index with the specified length.

Syntax

Below is the syntax of the PowerShell substring() method.

$string.Substring(startIndex)
$string.Substring(startIndex, length)

Parameters

• startIndex: The zero-based starting position of the substring in the original string.
• length: (Optional) The number of characters to include in the substring. If omitted, the substring extends from the startIndex to the end of the string.

Examples of Substring() in PowerShell

Now, let us check an example of a substring() in PowerShell. We will do all the operations using the below sting.

$names = "John, Emily, Michael, Sarah, David"

Extract from a Specific Index to the End

Suppose we want to extract all names starting from “Emily”. Below is the complete script.

# Original string
$names = "John, Emily, Michael, Sarah, David"

# Extract substring starting from index 6 to the end
$substring = $names.Substring(6)
Write-Output $substring

In this example, the substring starts at index 6 and includes all characters to the end of the string. Once you execute the above PowerShell script using VS code, it will give the below output:

Emily, Michael, Sarah, David

You can also see the output in the screenshot below:

Extract a Substring with a Specific Length

Let us check out another example of how to extract a substring with a specific length.

Let’s extract just the name “Emily” from the above string.

Below is the complete PowerShell script.

# Original string with USA-based names
$names = "John, Emily, Michael, Sarah, David"

# Extract substring starting from index 6 with length 5
$substring = $names.Substring(6, 5)
Write-Output $substring

Here, the substring starts at index 6 and includes the next 5 characters.

You can see the output in the screenshot below after I expected the script:

Extract the Last Name from the String

To extract the last name “David”, we need to calculate the starting index and use the Substring method; below is the complete script.

# Original string with USA-based names
$names = "John, Emily, Michael, Sarah, David"

# Calculate the starting index for "David"
$startIndex = $names.LastIndexOf("David")

# Extract substring starting from the calculated index
$substring = $names.Substring($startIndex)
Write-Output $substring

Extract a Specific Name by Index

If we want to extract “Michael”, we can specify the start index and length in PowerShell.

Below is the complete script.

# Original string with USA-based names
$names = "John, Emily, Michael, Sarah, David"

# Extract substring for "Michael"
$substring = $names.Substring(13, 7)
Write-Output $substring  # Output: "Michael"

Error Handling While Using Substring() Method

It is always good to manage error handling while using the PowerShell Substring() method.

It’s important to ensure that the startIndex and length parameters are within the bounds of the string to avoid errors. PowerShell will throw an ArgumentOutOfRangeException if the indices are invalid.

Check String Length

Before extracting a substring, you can check the length of the string to avoid errors. You can follow the below script.

# Original string with USA-based names
$names = "John, Emily, Michael, Sarah, David"

# Parameters for extracting a substring
$startIndex = 13
$length = 7

# Check if the startIndex and length are valid
if ($startIndex -lt $names.Length -and $startIndex + $length -le $names.Length) {
    $substring = $names.Substring($startIndex, $length)
    Write-Output $substring  # Output: "Michael"
} else {
    Write-Output "Invalid start index or length."
}

This script ensures that the startIndex and length are valid for the given string, preventing runtime errors.

Conclusion

The Substring() method in PowerShell extracts parts of a string. In this tutorial, I have explained how to use the PowerShell String() method with various examples and how to handle errors while using the substring() method in PowerShell.

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