Script to add day not date to filename - powershell

Question

I need to create a script batch, PowerShell or VB to add the day of the week to the filename.
For example, there are 4 files and all need to have MON apended to the front on Mondays, TUE on Tuesdays, WED on Wednesdays, etc.
Can anyone assist with this please?

Answer 1

$dow = (Get-Date -f ddd).ToUpper()
$fileName = "${dow}_your_file_name.txt "
THU_your_file_name.txt

Answer 2

Use the VBScript Docs or Google for details on the Weekday() and WeekdayName() functions used in:
Today = Date()
DayNum = Weekday(Today)
DayName = WeekdayName(DayNum, True)
WScript.Echo UCase(DayName) & "_" & "somefile.txt"
THU_somefile.txt
PS:
Start here: Functions (VBScript)

Answer 3

Well, there's an answer for powershell and one for VBScript. Here's one for Windows cmd batch.
#echo off
setlocal
for /f "tokens=5" %%I in ('find "" "%date:~0,3%" 2^>^&1') do set day=%%I
ren "oldfile.txt" "%day%_oldfile.txt"
Explanation
:: DIRECTIVE RESULT
:: --------------------------------------------------------
:: %date% Thu 02/07/2013
:: %date:~0,3% Thu
:: find "" "Thu" error stating "File not found - THU"
:: --------------------------------------------------------
Then all that remains is to redirect the error from stderr to stdout and scrape the fifth token.
(source of idea to use find to convert to upper case)

Answer 4

if you choose VBScript, be careful with WeekDayName function as it related to regional language settings. For example, Friday is Петък (in Bulgarian), so in my system WeekDayName with abbreviate set to True will return Пт, not Fri.
WScript.Echo WeekDayAbbrENG()
Function WeekDayAbbrENG()
Dim WDs
WDs = Split("SUN MON TUE WED THU FRI SAT")
WeekDayAbbrENG = WDs(Weekday(Now) - 1)
End Function
[EDIT] Actually, the same problem appear with Get-Date in PowerShell.