Powershell Powers, Activate!

Yesterday, I had a problem to solve. I didn’t want to stay at work until 9pm, waiting for another team’s process to publish a file. (Grossly simplified, but you get the idea). I also didn’t want to log in from home at 9pm in order to wait for it to happen (I did that the night before).

So I used Powershell! Could I have used a batch file? Of course! However, I know with Powershell I can just chain commands together via a semi-colon.
I searched for “Powershell sleep”, and saw immediately that there was, in fact, a Powershell sleep command: start-sleep.

My final commandline:
start-sleep -s 7000 ; GetFileCommand ; msbuild /t:clean,build

And I could just walk away, knowing it would be waiting for me when I got into today.

(That didn’t happen, but it was unrelated to the Powershell issue.)

However, that wasn’t my only use of Powershell yesterday. The MSBuild Project system defines a build through a series of linked .XML files. I uncovered an issue where a particular task wasn’t being completed as I expected. I could, through the wonders of “Find”, locate where I EXPECTED the work to be taking place, but in a 10,000+ line XML file, scrolling upward to find the parent is not entirely pleasant.

So I used code.

I read the XML into an XML object, then found the tag I was looking for. I then got an XML Navigator object for where I was in the document, and walked back up the tree until I found something identifiable (it turned out I was screwed). All told, it took me less time to puzzle out (via get-member) how to do so under Powershell than it would have taken for me to write a real program, or to find it by hand.

Here’s the entirety of what I wrote:
$xmldoc = [xml] [string]::join(“`n”, (gc -read 10kb Native.Build.targets))
$xmldoc | get-member
$xmldoc.GetElementsByTagName(‘Internal_LinkOutputFile’)
$xmldoc.GetElementsByTagName(‘Internal_LinkOutputFile’) | get-member
$xmldoc.GetElementsByTagName(‘Internal_LinkOutputFile’).Item(0)
$xmldoc.GetElementsByTagName(‘Internal_LinkOutputFile’).Item(0) | get-member
$nav = $xmldoc.GetElementsByTagName(‘Internal_LinkOutputFile’).Item(0).CreateNavigator()
$nav
$nav | get-member
$nav.MoveToParent()
$nav
$nav.MoveToParent()
$nav

There was an awful lot of get-member calls, but I didn’t need to know ANYTHING else.

Yay Powershell!