Tuesday, February 25, 2014
Powershell functions are much more advanced and allow some great capabilities for re-use. As I create useful functions, I will wrap them up and post at our new blog location for you all to enjoy.
I can't wait to get up to speed and share my new adventures with you all!
See you soon,
Oh, guess you probably need a link to the new Adventures in Powershell
Saturday, May 4, 2013
Friday, April 20, 2012
If you stumbled across this post, be glad you did. There are a few times in a scripters life where a script goes out and something breaks. Usually it’s the code not working and it’s a matter of finding the bug and fixing it. And then there is a worst case scenario where your code breaks every computer in the company.
This is that case.
Now before I continue, I should stress the script in question was not created by me. I’m very careful about file paths but this particular coder was not.
So this person’s script, let’s call him Bob, had a sub routine that was designed to take in a folder path, enumerate the files in that path, and delete them. Many of us have similar code and there is certainly nothing wrong with putting this in a sub routine. Let’s look at some example code:
strFolderPath = “C:\Temp”
set objFSO = CreateObject(“Scripting.FileSystemObject”)
set objFolder = objFSO.GetFolder(strFolderPath & “\”)
In the example above, Bob sets the C:\Temp folder path to strFolderPath. Next he properly initializes the FSO object. The last line is correct too, however, he appended the file path to add a backslash. Here’s the problem: If the strFolderPath variable never gets set, the net file path used by objFSO.GetFolder is “\”.
Why is a net path of “\” a bad thing? The script engine treats “\” as a valid file path to the root of the drive. Now, remember what Bob’s sub routine was designed to do. After it connected to a valid file path, it enumerated every file in that path and deleted them. Now you’ve got a real problem. Then consider that the root folder also contains your boot files. If that machine reboots, it will not boot back up until those files are replaced. Now you’ve got an even bigger problem. Then start thinking about how many machines this code has touched as part of some GPO or logon script and you’ve got one really bad week.
So what should Bob have done? Well first off, he never should have appended a file path with a backslash. In the old days of command lines, that was sometimes needed to make copy and delete routines know your target was a folder, not a file. But the FSO is much more exact that that. If you tell it to GetFolder, it won’t GetFile. There is no need for a backslash on the of a file path. Even if you think you are saving some time, don’t.
Also, since this was a sub routine, Bob could have added a quick line to the top of his script that would have checked the folder path variable before doing anything with it. Such as If Not objFSO.FolderExists(strFolderPath) Exit Sub. It’s not the most elegant way to check but it would have prevented the problem. If you absolutely knew you’d never ever connect to the root of a drive to delete files, you could even add If Len(strFolderPath) <4 Then Exit Sub. This would also have worked since the root paths are generally in the format of C:\.
So remember, be very careful in your file paths and if you are ever deleting files from FSO, remember to always try and break your own code before someone else does.