Powershell删除除某些符合特殊日期条件的文件外的所有文件

Question

I've a scenario. Before moving to that, let me say I need a logic as well from here. I've tried something (which I will tell shortly), but that doesnt seems to be working.

I've some files which is getting created each hour. I am scripting (powershell) to delete those in the way given below:

Out of 24 files created in a day, I need to keep only 1 (which is the last and latest created, need to delete other 23) daily for an entire week. This is DONE.

Now, on a weekly basis I need to do this in such a way that every saturday night, I need to delete 6 daily files and retain the latest one (of day 7). I am stuck here.

What I've tried is like using $date.AddDays(-1) which is okay for the first week. Second week, I need to retain last week's (1) file and need to retain this week's (1) file. So, here I am running out of logic.

In the same scenario I need to have it monthly also. I think I can get this done if I get some logic for weekly (which is in Bold ).

Can anyone please help me at the earliest. Any suggestions or thoughts would be really appreciated.

Answer 1

Why bother calculate anything? Takes advantage of powershell's power :) !
Get a date (from a file, from a var, or whatever) cast it do datetime and display the dayOfWeek property

([system.datetime]"09/07/2015").DayOfWeek

Answer 2

Forigve me if I got lost in all the comments but you could use this to get all the dates in the current month that are saturdays.

$now = Get-date
1..[DateTime]::DaysInMonth($now.Year,$now.Month) | ForEach-Object{get-date -day $_} | Where-Object{$_.DayOfWeek -eq "Saturday"}

So for July 2015

Saturday, July 04, 2015 8:22:53 AM
Saturday, July 11, 2015 8:22:53 AM
Saturday, July 18, 2015 8:22:53 AM
Saturday, July 25, 2015 8:22:53 AM

Of course you might want just the days so we can just add to the end of this. Select-Object -ExpandProperty Day .

4
11
18
25

You can now use those values in you date exclusion logic. Which could be useful if you are trying to compare dates ahead of time. Still PowerShell already has logic to caluculates individual dates to see if they are "saturday". So like Kayasax was suggetsting

Get-ChildItem *.* | Where-Object{ $_.lastwritetime.dayofweek -notmatch "saturday"} |select-object -expandproperty fullname

And add other date logic for hour or what not as required.

Answer 3

Start with the logic of the part you have already built, which is to group together files that were created in the same day, and retain only the latest file out of each group. This undoubtedly depends on converting the timestamp of the file's creation into a date.

What you need is a function, call it "week" which, given a date, returns the week number. So, for dates from Jul-5-2015 through Jul-11-2015, it might return the number "27", meaning the 27th week of the year.

Now create logic similar to the logic of what you have already built. But, instead of grouping by day, group by week number.

If you intend to keep this data for more than a year, you need to do something like the first week of next year returns "53".