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.
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.
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.
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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
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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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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.
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:
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.
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.
-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.
If you like this page then please share it with your friends
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.
Windows Management Instrumentation (WMI) is one of the hidden
treasures of Microsoft operating systems.
Fortunately, Solarwinds
have created the
Free WMI Monitor so that you can actually see and understand these gems of
performance information. Take the guess work out of which
WMI counters to use for applications like Microsoft Active Directory,
SQL or Exchange Server.
