We are finishing up day 1 here in my PowerShell class in Hunt Valley, MD. Just finished up calculated properties and had a request to expand the demonstration that I used a bit. We were using the Get-History cmdlet to explore calculated properties. Here is the code and output that we had:
Get-History |
Select-Object -Property CommandLine,
@{N="ExecutionTime";
E={$_.EndExecutionTime - $_.StartExecutionTime}} |
Sort-Object -Property ExecutionTime -Descending |
Select-Object -First 5
CommandLine ExecutionTime
----------- -------------
Show-Command 00:01:48.0548277
Update-Help 00:00:27.2509743
Get-Process | Select-Object -Property... 00:00:07.7695634
Get-Service -Name BITS | Stop-Service... 00:00:05.8634245
get-eventlog 00:00:05.4523953
The question came up if there is an easier way to display the ExecutionTime property. Our first step was to pipe this information to Get-Member to see the object type.
Get-History |
Select-Object -Property CommandLine,
@{N="ExecutionTime";
E={$_.EndExecutionTime - $_.StartExecutionTime}} |
Sort-Object -Property ExecutionTime -Descending |
Select-Object -First 5 |
Get-Member
TypeName: Selected.System.Management.Automation.PSCustomObject
Name MemberType Definition
---- ---------- ----------
Equals Method bool Equals(System.Object obj)
GetHashCode Method int GetHashCode()
GetType Method type GetType()
ToString Method string ToString()
CommandLine NoteProperty System.String CommandLine=Show-Command
ExecutionTime NoteProperty System.TimeSpan ExecutionTime=00:01:48.0548277
I highlighted in red the object type. Our next step was to extract the value of this property and send it to Get-Member to see what properties we had to work in the object type System.TimeSpan. As an alternate to this next step, just go to MSDN and look up the .NET object System.TimeSpan.
Get-History |
Select-Object -Property CommandLine,
@{N="ExecutionTime";
E={$_.EndExecutionTime - $_.StartExecutionTime}} |
Sort-Object -Property ExecutionTime -Descending |
Select-Object -ExpandProperty ExecutionTime |
Get-Member
TypeName: System.TimeSpan
Name MemberType Definition
---- ---------- ----------
Add Method timespan Add(timespan ts)
CompareTo Method int CompareTo(System.Object value), int CompareTo...
Duration Method timespan Duration()
Equals Method bool Equals(System.Object value), bool Equals(tim...
GetHashCode Method int GetHashCode()
GetType Method type GetType()
Negate Method timespan Negate()
Subtract Method timespan Subtract(timespan ts)
ToString Method string ToString(), string ToString(string format)...
Days Property int Days {get;}
Hours Property int Hours {get;}
Milliseconds Property int Milliseconds {get;}
Minutes Property int Minutes {get;}
Seconds Property int Seconds {get;}
Ticks Property long Ticks {get;}
TotalDays Property double TotalDays {get;}
TotalHours Property double TotalHours {get;}
TotalMilliseconds Property double TotalMilliseconds {get;}
TotalMinutes Property double TotalMinutes {get;}
TotalSeconds Property double TotalSeconds {get;}
We decided that the property TotalSeconds would be the best one to use in our scenario. In the Expression of the calculated property in line 4, we encapsulate our original expression inside of parenthesis. This allowed us to dot out the property of TotalSeconds from the object with minimal adjustment to our code.
Get-History |
Select-Object -Property CommandLine,
@{N="ExecutionTime";
E={($_.EndExecutionTime - $_.StartExecutionTime).TotalSeconds}} |
Sort-Object -Property ExecutionTime -Descending |
Select-Object -First 5
CommandLine ExecutionTime
----------- -------------
Show-Command 108.0548277
Update-Help 27.2509743
Get-Process | Select-Object -Property... 7.7695634
Get-Service -Name BITS | Stop-Service... 5.8634245
get-eventlog 5.4523953
And there you have it. If you have several ideas on how to accomplish a task, you can use this method to determine which one is most efficient. You may need to utilized TotalMilliseconds in a test environment for greater precision. If your task includes reaching out to clients on the network, the network traffic and client availability will have an effect on the times reported. It is best to test on a local system to determine the most efficient command.
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