My command seems to behave differently depending on how many items were returned. <\/i><\/p>\n
This is something that the PowerShell Team hears from the community or our internal partners every couple of weeks. This blog post will explain when a Windows PowerShell command returns different types and offer some reasons for why it is done this way.<\/p>\n
In general, Windows PowerShell commands can return one of three things: <\/p>\n
Executing the commands below returned each of the types listed above. <\/p>\n
\n(Get-Service<\/font> foobar<\/font>).GetType()
(Get-Service <\/font>NetLogon<\/font>).GetType()
(Get-Service<\/font> Net<\/font>*<\/font>).GetType() <\/font><\/p>\n<\/blockquote>\nCompare this to executing a WMI query in VBScript. Because you always get an array back, administrators have to litter their scripts with useless for-each loops. An extreme example is shown below, where the WMI query gets the Win32_OperatingSystem class to compute system uptime. It returns an array, even though there can never be multiple Win32_OperatingSystem items.<\/p>\n
\nSet colOperatingSystems = objWMIService.ExecQuery _
("Select * from Win32_OperatingSystem")<\/font><\/p>\nFor Each objOS in colOperatingSystems
dtmBootup = objOS.LastBootUpTime
dtmLastBootupTime = WMIDateStringToDate(dtmBootup)
dtmSystemUptime = DateDiff("h", dtmLastBootUpTime, Now)
Wscript.Echo dtmSystemUptime
Next<\/font><\/p>\n<\/blockquote>\nSince Windows PowerShell is also an interactive shell, we wanted to make it very easy for Administrators to work at the command line. A set of Windows PowerShell commands that do the same uptime calculation is shown below. Note that I didn\u2019t have to do any indexing or iterating over a collection.<\/p>\n
\n$os<\/font> = Get-WmiObject<\/font> Win32_OperatingSystem
<\/font>$lastBootup<\/font> = $os<\/font>.ConvertToDateTime($os<\/font>.LastBootUpTime)
$uptime<\/font> = ((Get-Date<\/font>) – $lastBootup<\/font>).TotalHours
Write-Host<\/font> $uptime<\/font><\/font><\/p>\n<\/blockquote>\nThis behavior allows for some fairly lazy, err\u2026 convenient interactive console experiences. For example, let’s say that I wanted to get the \u201cMicrosoft SharePoint Workspace Audit Service\u201d that is installed on my machine.<\/p>\n
\nGet-Service<\/font> \u2013Name
<\/font><\/font>…
Mcx2Svc
Microsoft SharePoint Workspace Audit Service
MMCSS
MpsSvc
\u2026<\/p>\n<\/blockquote>\nI can do that with very little typing:<\/p>\n
\n$svc <\/font>= <\/font>Get-Service<\/font> Mi*<\/font><\/font><\/p>\n<\/blockquote>\n
Here I used a wildcard expression (that, in many cases, would return multiple values) but Windows PowerShell returned a single object that I can work with directly. <\/p>\n