Scripting Files with PowerShell's Get-Childitem (gci)
Sooner or later you need a script which lists the files in a folder. In DOS we would type: 'DIR'; the nearest equivalent in PowerShell is gci. The full name behind the
gci alias is the
informative
Get-ChildItem. You can take the comparison further, dir /s in DOS, translates to Get-ChildItem -recurse in PowerShell.
Here
is an example to get started, it will list all the files in the C:\ root. If you need any help in executing the code, then see here.
# PowerShell script to list the files in C: root Get-Childitem "C:\"
Note 1: In this instance C:\ is the root and Get-Childitem lists any files in this directory.
Note 2: Get-Childitem "C:\" works equally well without the speech
marks. For example: Get-Childitem C:\ However, you do need the backslash after the colon.
Outside of PowerShell, recurse is a little known verb meaning rerun. Inside of PowerShell,
Get-ChildItem -recurse is one of the most famous parameters meaning: repeat the procedure on
sub-folders.
The point of example 2b is to list all the dll's under the
Windows folder. Moreover it will display the CreationTime, which can help determine if a file is up-to-date. This
technique is particularly useful for troubleshooting .dll files.
Example 2a - The Problem
Our goal is to find all the dlls under the Windows folder. The
problem is that this script does not search the system32 subdirectory.
# PowerShell gci example to list .dll in Windows folder $Files
= gci "C:\Windows\" | Where {$_.extension -eq ".dll"} $Files
| Format-Table Name, CreationTime, Length -auto
Note 3: This script lists only 4 dlls; surely there
must be more?
Note 4: I substituted the
alias gci for
Get-ChildItem
Example 2b - The Solution
To find .dlls in the subdirectories let us append the Get-ChildItem
-recurse parameter.
# PowerShell example to list .dll in Windows folder and sub-folders
Write-Host `n "Waiting ...." $Files = gci "C:\Windows\" -recurse |
Where {$_.extension -eq ".dll"} Clear-Host $Files | Format-Table
Name, CreationTime, Length -auto
Note 5: I changed Name to FullName so that it would
display the subdirectory where the file cold be found.
See more on $_.extension.
Example 2c - Extra Formatting
This example produces the same result but uses the -f formatting
command and the alias Gci.
# PowerShell script to list the dll files under C:\Windows\System32
$i =0 $Files = Gci "C:\Windows\" -recurse | ?
{$_.extension -eq ".dll"} Foreach ($Dll in $Files) { "{0,-28}
{1,-20} {2,12}" -f ` $Dll.name, $DLL.CreationTime, $Dll.Length
$i++ } Write-Host The total number of dlls is: $i
Note 6: This example also uses two aliases; my principle reason was to make line
3 shorter. Gci is an alias for our featured command Get-Childitem, and the question mark (?) is
an alias for 'where'.
Note 7: The -recurse parameter comes directly after the name of the directory. For completeness, the location should be introduced by the -path parameter, but as this is
optional, I have omitted the -path parameter in this script. However, this is how to include the -path parameter. $Files = gci -path "C:\Windows\System32" -recurse.
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When you discover a new
PowerShell command, it benefits from being probed with what I call the 'Trusty Twosome'. Experiment with Get-Help and Get-Member and unlock new scripting
possibilities for Get-Childitem. To see what I mean try these two commands:
# Research PowerShell Get-Childitem Parameters Get-Help Get-Childitem
# (Try help gci) If you prefer abbreviations. # (And help gci
-full) If you like examples.
Note 8: Get-Help unearths useful parameters such as -recurse, -exclude, it also reveals hidden files with: -force.
# Research PowerShell Get-Childitem Properties Get-Help Get-Childitem
Get-Childitem | Get-Member # (gci | gm) If you enjoy aliases. #
(gci | gm -Membertype property) If want only properties
Note: Get-Member reveals properties
that you don't normally see in explorer, for example, CreationTime.
$i=0 $GciFiles = Get-Childitem c:\ -force foreach ($file in $GciFiles) {$i++} $GciFiles | sort | ft name, attributes -auto Write-host "Number of files: " $i
Note 9: The key addition is the parameter -force. What this does is include hidden and system files.
Note
10: The additional commands enable us to count the
files, this makes easier to see prove that -force really makes a difference. Double check what I mean by running the script with, and
then without, the -force switch.
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# PowerShell cmdlet to list the System files in the root of C:\ $i=0 $GciFiles = Get-ChildItem "c:\" -force |where {$_.attributes -match "System"} foreach ($file in $GciFiles) {$i++} $GciFiles |sort |ft name, attributes -auto Write-host "Number of files: " $i
Note 11: We need to employ the comparison parameter -match "System", rather than -eq "System", this is because System files also have Hidden and other attributes. Consequently, their
attribute does not equal ''System'', although it does contain, or match the word System.
Note
12: You probably worked it out for your self, but just to emphasise that the variable $i is a counter.
Moreover, ++ increments $i each time the 'where' statements makes a match. Incidentally, omitting $=0 at the beginning produces an unexpected, or undesirable result when you run the script for a
second time.
Challenge 1: Repeat the command with and without -force.
Challenge 2: Substitute this new 'where' clause on line 3: where {$_.attributes -ne
"Directory"}. -ne is the opposite of -eq. Thus this command filters out the directory entry.
# PowerShell cmdlet to list the System files in the root of C:\ $i=0 $GciFiles = gci c:\ -force |where {$_.attributes -ne "Directory"} foreach ($file in $GciFiles) {$i++} $GciFiles |sort |ft name, attributes -auto # $GciFiles |Get-Member $i
Get-Childitem -recurse can be surprisingly tricky, if this construction is giving you problems, see here for more help on -recurse
»
The Rest of the Item Family
# PowerShell Item Cmdlet Research Clear-Host Get-Command
-noun Item
As expected there is an Get-Item cmdlet, but you may not realize there
is a Move-Item cmdlet. PowerShell -noun or -verb research
always throws up at least one surprise.
With Microsoft, there are always at least three ways of doing
everything, what seems like redundancy when you are an expert, seems like
perspective when you are a beginner. Get-ChildItem has not one, but
three aliases check thus:
# PowerShell Alias GCI Get-Alias
-definition Get-ChildItem
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.
