This one is more of an exercise, as in “can it be done?”. A few days ago, I was testing a service. I had to stop it, start it, stop it, start it, and so on. Automation is all about cutting down repetitive tasks. And it appeared to me that typing the following was very repetitive:
Get-Service SvcName | Stop-Service
Get-Service SvcName | Start-Service
(For some reason, that’s close to what I had to type, rather that Stop-Service SvcName and Start-Service SvcName)
I wondered: can I cut down the typing? After all, as once said Saint Jeffrey Snover:
The secret is that the best engineers are lazy. They love automation & will spend days to automate something. https://t.co/X1Ab8pNURk
— Jeffrey Snover (@jsnover) July 17, 2015
Ok, spending days on that would have been a bit much, but it stayed somewhere on my mind. I had an idea about how to do it, but didn’t see how to use the pipeline for a cmdlet you had the name of in a string. Then while falling asleep yesterday: it dawned to me: alias…
Suppose you have, say, a service. It has a type:
PS> $svc = Get-Service SvcName
PS> $svc.GetType()
IsPublic IsSerial Name BaseType
-------- -------- ---- --------
True False ServiceController System.ComponentModel.Component
You can get commands by parameter type:
PS> Get-Command -ParameterType $svc.GetType()
CommandType Name Version Source
----------- ---- ------- ------
Cmdlet Get-Service 3.1.0.0 Microsoft.PowerShell.Management
Cmdlet Restart-Service 3.1.0.0 Microsoft.PowerShell.Management
Cmdlet Resume-Service 3.1.0.0 Microsoft.PowerShell.Management
Cmdlet Set-Service 3.1.0.0 Microsoft.PowerShell.Management
Cmdlet Start-Service 3.1.0.0 Microsoft.PowerShell.Management
Cmdlet Stop-Service 3.1.0.0 Microsoft.PowerShell.Management
Cmdlet Suspend-Service 3.1.0.0 Microsoft.PowerShell.Management
You can get commands by verb, too:
PS> Get-Command -Verb stop
CommandType Name Version Source
----------- ---- ------- ------
Function Stop-BgpPeer 3.0.0.0 RemoteAccess
Function Stop-DscConfiguration 1.1 PSDesiredStateConfiguration
Function Stop-Dtc 1.0.0.0 MsDtc
Function Stop-DtcTransactionsTraceSession 1.0.0.0 MsDtc
...
Now suppose you write a function, called Stop-Something. In it, you get the type of objects sent in the pipeline, find the command whose verb is ‘Stop’ that accepts that particular type. Stop-Something is no shorter to type than Stop-Service, so you just create a Stop alias:
Get-Service SvcName | Stop
Get-Process Notepad | Stop
Nice. All that’s left to do is to create a function for Stop, one for Restart, etc. Wait, they would all be the same, but for the verb used. And another thing you can do, is to get the verb of your current function:
PS> Function Get-Lazy {
>> $MyInvocation.MyCommand.Verb
>> }
PS> Get-Lazy
Get
Now you can have one single scriptblock with the function definition, and create those on the fly. I had to take into account the fact that some verbs are well-known aliases or reserved words, and because I just wrote it very quickly, I don’t really handle the case where there would be several commands that fit, but here is a result (Oh, BTW, did you know that Something is always an alias for Get-Something?):
PS> service BITS | restart
PS> module MyTools | remove
PS> job 5 | stop
PS> ps | ? responding -EQ $false | stop # it handles the pipeline, too.
I put the whole thing in a gist: