Tuesday, July 1, 2008

Powershell functions: whoami and Prompt

Two quick ones for this post, before the US 4th of July holiday. Both functions have one thing in common: use of environment variables. In order to see the environment variables that are available, just type:
dir env:

(This listing could be extensive. (dir env:).Count returns 51 on my laptop.)

Environment variables aren't as popular as they used to be, with settings located in registry entries, .ini files and .xml files. For a few things, it's still easier to find their values through an environment variable than to figure out where they hide in the registry or google for the proper .net calls. When I set up a new machine, I add a path to the environment that points to my local copy of my scripts. This can be very handy since I still have some .vbs and .wsf scripts lurking around.

whoami simply displays the name of the currently logged in user. It's very simple, but it is also a good, simple example of how to use environment variables in a script.

Here is the function:
function whoami {
$env:userdomain + "\" + $env:username

I often use $env:userdomain as a default for parameters of functions that look up information about domain users and groups. With most of my clients, the chances are that the user or group that I am interested in will be in my domain.

Prompt functions are another one of those things that everyone writes. Some are sparse, some are colorful and some display so much information that they can be confusing to anyone but the original author. Mine is fairly sparse:

function prompt {
$host.ui.RawUI.WindowTitle = "psh"
$promptText = "[" + $env:username + "@" + $env:COMPUTERNAME + " @" + $(get-date -uformat "%H:%M:%S")
write-host $promptText -NoNewLine
write-host " $(get-location)" -NoNewLine -ForeGroundColor Cyan
write-host "]"

I'm on the fence about whether the two-live format is a good idea or not. I include the time as a sort of poor-mans stop watch. It lets me get an idea for a when a command stopped without actually timing it and without getting too fancy in the prompt code.

That's all for this posting.
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