PowerShell Scripting  -Recurse

Introduction to PowerShell Scripting -Recurse

When you want a PowerShell command to search sub-directories -Recurse is a life saver.  In other contexts this concept is called iteration, or sub-directory recursion.  The cmdlet which benefits most from the -Recurse parameter is Get-Childitem.

Topics for PowerShell -Recurse Parameter

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Example 1 Get-ChildItem -Recurse

Our mission is to list all the Windows files under the Program Files folder.  It was the positioning of -Recurse that gave me my biggest headache.  My tactical error was to try and introduce -Recurse into a long statement.  What I should have done was take my own advice and build up gradually like this:-

Stage 1 Problem: The script lists files only in the top level directory.

# PowerShell With Just Get-ChildItem (no recurse)
Clear-Host
Get-ChildItem -path "C:\Program Files\"

Note 1: Get-Childitem is the equivalent of dir.  In fact PowerShell creates an alias called dir, thus this old command still works on the command line.

Stage 2 Solution: -Recurse drills down and finds lots more files.

# PowerShell -Recurse parameter
Clear-Host
Get-ChildItem -path "C:\Program Files\" -Recurse

Note 2: The key to -Recurse is the position, it has to be directly after the directory.  In this example I have explicitly used -path to define the location.

Stage 3a Precise Solution:  -Recurse with a filter and wildcard* on the directory name.

# PowerShell -Recurse parameter
Clear-Host
$Directory = "C:\Program Files\Windows*"
Get-ChildItem -path $Directory -Recurse

Note 3: I wanted to highlight the path be assigning it to a variable, and thus make it easier for you to change the path to suit your task.

Stage 3b Filter for Executables

# PowerShell -Recurse parameter
Clear-Host
$Directory = "C:\Program Files\Windows*"
Get-ChildItem -path $Directory -Recurse -Include *.exe

Stage 3c  Neatly Sorted

# PowerShell -Recurse parameter
Clear-Host
$Directory = "C:\Program Files\Windows*"
Get-ChildItem -path $Directory -Recurse -Include *.exe `
| Sort-Object Name | Format-Table Name, Fullname -auto

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Example 2 Searching The Registry with -Recurse

In addition to the file system, Get-ChildItem can work with the registry

# PowerShell Script To Search The Registry
Clear-Host
$Path = "HKLM:\Software\Microsoft\PowerShell"
Get-ChildItem $Path -Recurse

Example 3 More Complex Example

I only include this example to explain how difficult it can be to decide where to place -Recurse.  When you study that long middle line you can see how it's possible to group the output and select a custom Format-Table (ft).

# PowerShell script to find executable in the Windows folder
Clear-Host
$Path = "C:\Windows\System32"
Get-Childitem $Path -Recurse | where {$_.Extension -Match "exe"}`
 | ft -group {$_.Path} Directory, Name -autosize

Note 4:  You can improve this script by adding -ErrorAction to skip the error message on protected or in use executables.

# PowerShell script to find executables in the Windows\System32 folder
Clear-Host
$Path = "C:\Windows\System32"
Get-Childitem $Path -Recurse -ErrorAction SilentlyContinue |`
where {$_.Extension -Match "exe"} | ft -group {$_.Path} Directory, Name -auto

See how to add -ErrorAction SilentlyContinue if you get problems.

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Troubleshooting PowerShell -Recurse

The problem with the -Recurse parameter is that it only works where the object has leaf items, for example:
C: \Windows\  -Recurse.  My point is, I was caught out by trying C: \Windows\*.dll -Recurse.

To see my point try these two examples:

# PowerShell recurse finds executables under the Windows folder
Clear-Host
$Path = "C:\Windows\*.exe"
$WinExe = Get-ChildItem $Path -Recurse
$WinExe.count

Note 5: The answer was only about 17.  This script lists .exe files only in the actual Windows folder.  -Recurse is useless here.

# PowerShell script to find ALL executables under Windows folder
Write-Host "Waiting for -Recurse ..."
$Path = "C:\Windows\"
$WinExe = Get-Childitem $Path -Recurse -ErrorAction SilentlyContinue `
| Where-Object {$_.Extension -Match "exe"}
Clear-Host
$WinExe.count

Note 6:  Expected answer over 2,000.  -Recurse does its job.  'Where-Object' plays its role in filtering.  Alternatively, you could employ the -Include parameter.

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Scope of the -Recurse Parameter

While -Recurse works nicely for the above Get-Childitem, I emphasise CHILDitem.  I could neither get it to work with Get-Item, nor could I see -Recurse amongst the parameters for plain Get-Item.

Research: Find PowerShell -Recurse Cmdlets

Clear-Host
Get-Command -CommandType cmdlet `
| where { $_.parameters.keys -Contains "recurse"}

Incidentally, Get-Childitem | Get-Member does not, repeat not, list -Recurse.  This is because -Recurse is a parameter, or what I call a switch.  Get-Member lists methods and properties, but not parameters, to see more about -Recurse you need:

Clear-Host
Get-Help Get-Childitem

Problems with -Recurse, and How to Overcome Them

Case Study
The mission is to list all files containing the word 'Microsoft' in the Windows folder or its sub-folders.  For this we use the select-string pattern matching command.

The problem is that this script does not work.  All that happens is that we get an error: Cannot find path... Path does not exist.

# PowerShell -Recurse example
Clear-Host
$i=0
$Path = "C:\Windows"
$Full = Get-ChildItem $Path -Recurse
$StringText = "Microsoft"
$List = select-string -pattern $StringText $Full
foreach ($file in $List) {$file.Path; $i++}
$i

The Solution: Add the -Include parameter

Clear-Host
$i=0
$Path = "C:\Windows"
$Full = Get-ChildItem $Path -Include *.txt -Recurse
$StringText = "Microsoft"
$List = select-string -pattern $StringText $Full
foreach ($file in $List) {$file.Path; $i++}
$i

Note 7:  When we add -Include *.txt the cmdlet works as initially planned.  Actually, you could swap the famous *.* for *.txt, thus : -Include *.*

Note 8: -Include only works when you also append the -Recurse parameter.

Note 9: -Include applies to the filename and extension.  Where I made a mistake was thinking that -Include would apply to the path.

Simplification
There is no reason why you cannot simplify the above example by removing at least two of the variables, especially on a production script.  The only reason that I employed $Path and $StringText is that when I am creating a script I like to isolate and control each step of the way.

$i=0
$Full = Get-ChildItem C:\windows -Include *.txt -Recurse
$List = select-string -pattern "Microsoft" $Full
foreach ($file in $List) {$file.Path; $i++}
$i

See more on Get-ChildItem -Filter parameter »

Summary of PowerShell -Recurse

-Recurse is a classic switch, which instructs PowerShell commands such as Get-ChildItem to repeat in sub directories.  Once you remember that -Recurse comes directly after the directory, then it will serve you well in scripts that need to drill down to find information.

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See more Microsoft PowerShell file tutorials:

PowerShell Home    • PowerShell Backup Copy-Item   • PowerShell Files  • Free Import CSVDE Tool

PowerShell Registry  • Get-Credential  • PowerShell ItemProperty   • PowerShell -Recurse

PowerShell Get-ChildItem  • PowerShell -Filter   • Free Permissions AnalyzerCompare-Object

Please email me if you have a better example script. Also please report any factual mistakes, grammatical errors or broken links, I will be happy to correct the fault.

 

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