PowerShell Script to List Files

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PowerShell Script to List Files

These examples explain how to get started scripting files with PowerShell.  Because I dislike 'Hello World' examples, my scripts have a practical purpose, in this instance to get a listing of a particular type of file, in a particular directory tree.

• Our PowerShell Mission
• Example 1 - Find all dlls in the Windows\System32 folder
• Example 2 - Discover Properties with: Get-Member
• Example 3 - Output to a file
• Summary of Using PowerShell to List Files

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Our PowerShell Mission

My mission is to list all files with a given extension in a particular directory tree.  Specifically, all dlls in the windows\windows32 folder.  This simple task is much like typing the DOS command: dir \s.  What would make my day is if you can alter my script to search for files that interest you.

My learning agenda for PowerShell is as follows:

1. To appreciate the rhythm of the PowerShell language.  Verb-noun pairs.
2. To demonstrate how easy it is to introduce $variables
3. To employ the flexibility of the pipe command (|) so that the output of the first command becomes the input of a second command.
4. To interrogate the capabilities of an object with get-Member.

Example 1 - Find all dlls in the Windows\System32 folder

Pre-requisites

You need to have already installed a local copy of PowerShell.  If necessary search the internet for 'Microsoft PowerShell download'.  Note PowerShell RC2 is much changed from its predecessor, release candidate 1.

Instructions

1. Save the following script to a text file with a .ps1 extension, for example: C: \Script\dll.ps1.
2. Launch PowerShell and navigate to the folder where you saved the .ps1 file.  Incidentally, the Dos cd command works fine in PowerShell.
3. To call for your script file, type at the command line PS> .\dll.ps1.
   Note 1. The rhythm of the command is:  dot slash filename.
   Note 2. You don't have to type PS>

Learning Points

Note 1: Beginning a script with cls is one of my idiosyncrasies, it simply means clear the screen of any previous output (just as it does in DOS).  The hash symbol # means a remark, or do not process this line.

Note 2:  $Dir = get-Childitem C:\windows\system32 -recurse
This command sets the variable $Dir to the path of the files that we seek.  You have probably guessed the purpose of the -recurse switch, to drill down to the sub-folders.  Get-childitem is often abbreviated to its alias, gci.

Note 3:  $List = $Dir | where {$_.extension -eq ".dll"}
$List is another variable whose purpose is to filter the output, as a result we get only files with .dll extension.  Pay particular attention to the construction $_. which means, in this pipeline.  Also observe that instead of the equals sign, PowerShell needs -eq.

Note 4:  One of PowerShell's features is the pipe symbol (|).  Most PowerShell scripts contain at least one pipe to control, or filter the output of the main command.

Note  Out-GridView: PowerShell v 2.0 introduces a new cmdlet to control data display.  See more on how to pipe the results into out-GridView.

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Example 2 - Discover Properties with: Get-Member

The purpose of this script is to list the properties of the file object controlled by the $dir variable.  When we display the list, how much information do we want?  What file properties are available?  All is revealed by get-Member.

Learning Points

Note 1:  This is the same script as example 1, all that has changed is the #.  I have 'remmed' out the list and activated the line: $Dir |get-Member.

Note 2:  Get-Member lists the properties and methods of the PowerShell object $Dir.  Once we have our list we can control the output specified by format-Table.  See next example.

Example 3 - Output to a file

Seeing the files on screen is fine, but with lists of files, it's often handy to generate a file containing your script's output.

Learning Points

Note 1:  Here is the line that I activated by removing the #. $List |ft fullname |out-file c: \Scripts\dll.txt.  What this does is create a file in the c: \Scripts folder.  (Note it does not create the \Scripts folder itself, you must do that yourself.) In that dll.txt file are the names of all the files with a .dll extension.

Note 2:  ft, meaning format-Table, is one of the built-in aliases which make the code shorter to write.

Guy's Challenges

Challenge 1:  Set the script to list a different extension, for example .com or .exe.

Challenge 2:  Persuade the script to output the 'length' property of the files.

Challenge 3:  Filter the object property with -MemberType, for example remove unwanted Methods leaving only 'Property':
$Dir |get-Member -MemberType property

Summary of Using PowerShell to List Files

PowerShell is a very efficient scripting language.  In this example we use $variables and verb-noun pairs to create a script which lists the files we seek.  I hope you will tweak my examples to list the types of files that you need.  Moreover, I hope that you can see how to adjust the variable, as a result you can locate a directory tree of your choosing.  As a bonus, Example 3 outputs the list of files, not to screen, but to a text file.

See more Microsoft PowerShell tutorials:

• PowerShell Home  • Com  • Shell Application  • Active Directory  • QAD Snap-in  • Get-Member

Please write in if you see errors of any kind.  Please report any factual mistakes, grammatical errors or broken links, I will be happy to not only to correct the fault, but also to give you credit.

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