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Monday, April 13, 2015

Unsafe Powershell Functions

Of recent I have been swimming in the deep end of the PowerShell pool. I discovered to my chagrin how some commands in PowerShell are unsafe. Let me describe what I mean by unsafe, as there are multiple interpretations depending on the context.


A unsafe command is one that interprets empty or undefined variable as to mean the wildcard * .


The example I got into this with is the Exchange 2010 Module's get-mailbox command. In this context "Get-MailBox $_"  is equal to "Get-Mailbox"   when $_ is undefined or blank.
This means the command pulls all mailboxes, rather that erring out, or querying for data.

One thing I realized is that you could protect the code with a conditional statement.
' where {$_ -NE ""} | Get-Mailbox $_ '
or for those of you who like to use short alias in your code
' ? {$_ -NE ""} | Get-Mailbox $_ '

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