How to Find Common File Names Between Two Arrays in PowerShell

Описание: Learn how to effectively compare two arrays in PowerShell to extract common file names, using a practical example.
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This video is based on the question https://stackoverflow.com/q/64331744/ asked by the user 'inquirymind' ( https://stackoverflow.com/u/12493323/ ) and on the answer https://stackoverflow.com/a/64332268/ provided by the user 'DEV-Jacol' ( https://stackoverflow.com/u/3046335/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

Working with arrays in PowerShell can sometimes be tricky, especially when you want to find common elements between two lists. If you're dealing with file names and their full paths, it's essential to extract those items that exist in both arrays. This is a common requirement for file management tasks and can be easily achieved with the right approach in PowerShell.

In this guide, we'll explore how to find all file names from one list that exist in another list, specifically using PowerShell. Let's break down the problem you're facing and provide a clear solution.

The Problem

Imagine you have two lists:

A list of file names (let's call it list1)

A list of full file paths (we'll call this list2)

Your goal is to extract the full file paths from list2 that correspond to the file names in list1. In simpler terms, you want to match the file names with their full paths to find out which files from your list of file names are present in the directory.

For example:

list1: index.jsp, index1.jsp, index2.jsp

list2: Full paths of files in your directory

The Solution

To achieve this, we can use a straightforward PowerShell script. The original attempt had some issues, but don’t worry—we’ll walk through a more effective method to accomplish this task.

Step 1: Define Your Arrays

First, we need to define our list of file names (list1). This is done using the @ () array notation.

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Step 2: Get the List of Full File Paths

Next, we will retrieve all files in the current directory and its subdirectories. This can be done using the Get-ChildItem cmdlet with the -Recurse and -File parameters, which ensures we only get files (and not directories).

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Step 3: Compare the Two Lists

Now, to find the common elements (i.e., the file paths that match any file names in our filenames list), we will use the Where-Object cmdlet and the -In operator. This allows us to filter the full paths based on whether their names exist in the filenames array.

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Step 4: Output the Results

Finally, to display the full paths of the matching files, simply output the FullName property of the $common variable.

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Full Working Example

Putting it all together, here’s the complete PowerShell script:

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Conclusion

By following the steps outlined above, you can effectively extract elements from one array that match elements of another array in PowerShell. This method not only saves time but also helps streamline your file management tasks.

Whether you're dealing with a small number of files or managing a vast directory structure, understanding how to work with arrays and filtering in PowerShell will be invaluable. We hope this guide has provided clarity on the process and equips you with the tools needed for future projects!