Trim date from file name using powershell or cmd - powershell

Question

How do you trim the date from a text file. For example, I have multiple files like:
test_20091011.txt
try_20091011.txt
fold_20091011.txt
I would like to change into:
test.txt
try.txt
fold.txt
Thanks.

Answer 1

This code should work assuming the text file name format doesn't change, as in, it's always the last 9 characters you need to remove. This code assumes the txt files are in the folder C:\folder
$filelist = (get-childitem c:\folder | Where-Object {$_.mode -match "a"} | foreach-object {$_.name})
foreach ($file in $filelist)
{
$len = $file.length
$newname = $file.substring(0,$len -13)
$newname = $newname + '.txt'
Rename-Item C:\folder\$file $newname
clear-variable newname, len
}

Answer 2

The answer for this will change subtly depending on the type of naming pattern, but in your case, you can accomplish this with a script like this:
Get-ChildItem |
Where-Object {
<#
Multiple Assignment in PowerShell.
$beforeUnderbar will have your name,
$AfterUnderBar will have the data, and
$extension will have the extension.
All from one little -split
If you start throwing random other files in there, it will barf.
#>
$beforeUnderbar, $afterUnderBar, $extension = ($_.Name -split "[_.]")
if ($afterUnderBar -and $afterUnderBar.Length -eq 8 -and $afterUnderBar -as [int]) {
"$beforeUnderBar.$extension"
}
}
That script should give you what you want from files that match your naming convention.