Using [IO.Path]::GetTempFileName()

..NET novice**

How does [IO.Path]::GetTempFileName() work? I'm trying to use it to avoid
some kind of race condition, but I need to call it, and get the resulting
temp file into a variable.

Then I'll come back later to actally use that temp file name by writing,
reading, and appending to it later. Eventually, I'll delete it.

I'm just wondering about the creation and deletion criteria, and how I make
sure I can't cause any conflicts by using multiple temp files.

Marco

Hi Marco,

> How does [IO.Path]::GetTempFileName() work? I'm trying to use it to avoid
> some kind of race condition, but I need to call it, and get the resulting
> temp file into a variable.
>
> Then I'll come back later to actally use that temp file name by writing,
> reading, and appending to it later. Eventually, I'll delete it.
>
> I'm just wondering about the creation and deletion criteria, and how I make
> sure I can't cause any conflicts by using multiple temp files.

[IO.Path]::GetTempFileName() internally calls the win32 API function
GetTempFileName. To avoid race conditions GetTempFileName actually
creates an empty file with the "temp file name". So if a file with that
name already exists (that is creating a _new_ file fails) an other name
is choosen until creating a new file with that name succeeds.
Well, at least that's how I would say GetTempFileName works...

btw By using the following expression you can clearly see that each call
to GetTempFileName actually creates an empty file:

ls ([IO.Path]::GetTempFileName())

hth

Max

"Marco Shaw" <marco@Znbnet.nb.ca> wrote in message news:eLNV4KbFHHA.3540@TK2MSFTNGP02.phx.gbl...
> .NET novice**
>
> How does [IO.Path]::GetTempFileName() work?

It creates the file as a zero length file with a guaranteed unique name.

"Hello" > $tempFile
"World" >> $tempFile

remove-item $tempFile

> I'm just wondering about the creation and deletion criteria, and how I make
> sure I can't cause any conflicts by using multiple temp files.

I don't think you will run into problems since GetTempFilename assures that you get a unique name. You could even use a trap to make sure the file get's cleaned up e.g.:

trap { if ($tempFile -ne $null) { remove-item $tempFile }; break}

$tempFile = [IO.Path]::GetTempFilename()
gci $tempFile
"Hello" > $tempFile
"World" >> $tempFile
gc $tempFile
gci $tempFile
throw "foo"
ri $tempFile
gci $tempFile

--
Keith