I'm going to start by saying I'm still pretty much a rookie at PowerShell and hoping there is a way to do this.
We have a utils.ps1 script that contains just functions that we dot source with in other scripts. One of the functions returns back a default value if a value is not passed in. I know I could check $args and such but what I wanted was to use the function for the default value in the parameters.
param(
[string]$dbServer=$(Get-DefaultParam "dbServer"),
[string]$appServer=$(Get-DefaultParam "appServer")
)
This doesn't work since the Util script hasn't been sourced yet. I can't put the dot source first because then params doesn't work as it's not the top line. The utils isn't a module and I can't use the #require.
What I got working was this
param(
[ValidateScript({ return $false; })]
[bool]$loadScript=$(. ./Utils.ps1; $true),
[string]$dbServer=$(Get-DefaultParam "dbServer"),
[string]$appServer=$(Get-DefaultParam "appServer")
)
Create a parameter that loads the script and prevent passing a value into that parameter. This will load the script in the correct scope, if I load it in the ValidateScript it's not in the correct scope. Then the rest of the parameters have access to the functions in the Utils.ps1. This probably is not a supported side effect, aka hack, as if I move the loadScript below the other parameters fail since the script hasn't been loaded.
PowerShell guarantee parameters will always load sequential?
Instead should we put all the functions in Utils.ps1 in global scope? this would need to run Utils.ps1 before the other scripts - which seems ok in scripting but less than ideal when running the scripts by hand
Is there a more supported way of doing this besides modules and #require?
Better to not use default value of params and just code all the checks after sourcing and check $args if we need to run the function?
It would be beneficial to instead turn that script into a PowerShell Module, despite your statement that you desire to avoid one. This way, your functions are always available for use as long as the module is installed. Also, despite not wanting to use it, the #Require directive is how you put execution constraints on your script, such as PowerShell version or modules that must be installed for the script to function.
If you really don't want to put this into a module, you can dot-source utils.ps1 from the executing user's $profile. As long as you don't run powershell.exe with the -NoProfile parameter, the profile loads with each session and your functions will be available for use.
Related
Using CmdletBinding, is there an easy way to regurgitate the exact parameters that a cmdlet was called with, so I can call another cmdlet with the exact same parameters?
I'm writing Powershell Cmdlets in Powershell. I'm using advanced functions. I have a cmdlet called Get-Environment, with several optional parameters like [string]EnvironmentName and [switch]Active. I have another cmdlet, called Get-Machine, with all of the same optional parameters; it calls Get-Environment. Originally, before I added the [switch]Active parameter, I simply called Get-Environment with all variables explicitly (see below).
I can't do the same thing now, because if I add "active" then it will be set. I don't want to have make a test in Get-Machine to see if Active is true and have two different versions of the Get-Environment call. I'd prefer to not have to trawl through the $PSBoundParameters hashtable and reconstruct the original strings, but that looks like the only feasible way forward (unless I'm missing something.)
Original code inside get-machine:
$environments = get-Environment -EnvironmentName $EnvironmentName
Oh for Pete's sake. I found it. I was missing the big stupid easy thing. I'll leave this up for others, and in case someone has an even better answer.
https://ss64.com/ps/psboundparameters.html
$PSBoundParameters can be used to call a subordinate function or cmdlet passing the same parameters - PowerShell will automatically splat the hash table's values instead of having to type each of the parameters:
get-otherthing #PSBoundParameters
In my new project team, for each powershell cmdlet they have written proxy function. When i asked the reason for this practice, they said that it is a normal way that automation framework would be written. They also said that If powershell cmdlet is changed then we do not need to worry ,we can just change one function.
I never saw powershell cmdlets functionality or names changed.
For example, In SQL powershell module they previously used snapin then they changed to module. but still the cmdlets are same. No change in cmdlet signature. May be extra arguments would have added.
Because of this proxy functions , even small tasks taking long time. Is their fear baseless or correct? Is there any incident where powershell cmdlets name or parameter changed?
I guess they want to be extra safe. Powershell would have breaking changes here and here sometimes but I doubt that what your team is doing would be impacted by those (given the rare nature of these events). For instance my several years old scripts continue to function properly up to present day (and they were mostly developed against PS 2-3).
I would say that this is overengineering, but I cant really blame them for that.
4c74356b41 makes some good points, but I wonder if there's a simpler approach.
Bear with me while I restate the situation, just to ensure I understand it.
My understanding of the issue is that usage of a certain cmdlet may be strewn about the code base of your automation framework.
One day, in a new release of PowerShell or that module, the implementation changes; could be internal only, could be parameters (signature) or even cmdlet name that changes.
The problem then, is you would have to change the implementation all throughout your code.
So with proxy functions, you don't prevent this issue; a breaking change will break your framework, but the idea is that fixing it would be simpler because you can fix up your own proxy function implementation, in one place, and then all of the code will be fixed.
Other Options
Because of the way command discovery works in PowerShell, you can override existing commands by defining functions or aliases with the same name.
So for example let's say that Get-Service had a breaking change and you used it all over (no proxy functions).
Instead of changing all your code, you can define your own Get-Service function, and the code will use that instead. It's basically the same thing you're doing now, except you don't have to implement hundreds of "empty" proxy functions.
For better naming, you can name your function Get-FrameworkService (or something) and then just define an alias for Get-Service to Get-FrameworkService. It's a bit easier to test that way.
One disadvantage with this is that reading the code could be unclear, because when you see Get-Service somewhere it's not immediately obvious that it could have been overwritten, which makes it a bit less straightforward if you really wanted to call the current original version.
For that, I recommend importing all of the modules you'll be using with -Prefix and then making all (potentially) overridable calls use the prefix, so there's a clear demarcation.
This even works with a lot of the "built-in" commands, so you could re-import the module with a prefix:
Import-Module Microsoft.PowerShell.Utility -Prefix Overridable -Force
TL;DR
So the short answer:
avoid making lots and lots of pass-thru proxy functions
import all modules with prefix
when needed create a new function to override functionality of another
then add an alias for prefixed_name -> override_function
Import-Module Microsoft.PowerShell.Utility -Prefix Overridable -Force
Compare-OverridableObject $a $b
No need for a proxy here; later when you want to override it:
function Compare-CanonicalObject { <# Stuff #> }
New-Alias Compare-OverridableObject Compare-CanonicalObject
Anywhere in the code that you see a direct call like:
Compare-Object $c $d
Then you know: either this intentionally calls the current implementation of that command (which in other places could be overridden), or this command should never be overridden.
Advantages:
Clarity: looking at the code tells you whether an override could exist.
Testability: writing tests is clearer and easier for overridden commands because they have their own unique name
Discoverability: all overridden commands can be discovered by searching for aliases with the right name pattern i.e. Get-Alias *-Overridable*
Much less code
All overrides and their aliases can be packaged into modules
I have a PowerShell module that contains a number of common management and deployment functions. This is installed on all our client workstations. This module is called from a large number of scripts that get executed at login, via scheduled tasks or during deployments.
From within the module, it is possible to get the name of the calling script:
function Get-CallingScript {
return ($script:MyInvocation.ScriptName)
}
However, from within the module, I have not found any way of accessing the parameters originally passed to the calling script. For my purposes, I'd prefer to access them in the form of a dictionary object, but even the original command line would do. Unfortunately, given my use case, accessing the parameters from within the script and passing them to the module is not an option.
Any ideas? Thank you.
From about_Scopes:
Sessions, modules, and nested prompts are self-contained environments,
but they are not child scopes of the global scope in the session.
That being said, this worked for me from within a module:
$Global:MyInvocation.UnboundArguments
Note that I was calling my script with an unnamed parameter when the script was defined without parameters, so UnboundArguments makes sense. You might need this instead if you have defined parameters:
$Global:MyInvocation.BoundParameters
I can see how this in general would be a security concern. For instance, if there was a credential passed to the function up the stack from you, you would be able to access that credential.
The arguments passed to the current function can be accessed via $PSBoundParameters, but there isn't a mechanism to look at the call stack function's parameters.
I am writing a powershell module with a list of utilties that I use on a daily basis. However, my question is: How can I not repeat so much code?
For example if I have a function that gets a list of hostnames from a file, I have to create that parameter in every single function. How can I just create it once, and then have each function prompt for it, or grab it?
function CopyFiles {
param (
[parameter(Mandatory = $true, HelpMessage = "Enter the Path to the Machine List File (UNC Path or local). ")]
[ValidateScript({$_ -ne ""})]
[string] $MachineListFilename,
...Sometime later in the script...
$MachineList = Get-Content $MachineListFilename
}
function DoSomeOtherTask {
param (
[parameter(Mandatory = $true, HelpMessage = "Enter the Path to the Machine List File (UNC Path or local). ")]
[ValidateScript({$_ -ne ""})]
[string] $MachineListFilename,
...Sometime later in the script...
$MachineList = Get-Content $MachineListFilename
}
It just seems really in-efficient to cut and paste the same code over and over again. Especially for something like, domain-name, username, password, etc.
Ultimately, I'm trying to get to a point to where I just write wrapper scripts for these functions once I import the module. Then I can just pass parameters via the command line. However, with the current way I'm doing it, the module is going to be littered with a lot of repetitive code, like parameters for username and password, etc.
Is there a better way?
Make your cmdlets/functions as independent and flexible as you can. Sometimes a wrapper function is the way to go, other times consolidating things into one function and calling it differently is more workable.
In the example you've given here, give the caller two options - you can pass in the filename for the list of machines, or pass in the list of machines. That way, you can read the file once in the calling script, and pass the array of machine names into each function. This will be much more efficient as you're only reading from disk one time.
I strongly recommend reading up on advanced functions and parametersets to simplify things (you'll need this for my suggestion above).
As for "repetitive code" - as soon as you find yourself copying/pasting code, stop. Find a way to make that code generic and move it into its own function, then call that function wherever it's needed. This isn't a PowerShell notion - this is standard programming, the DRY Principle.
Even then, you'll still find yourself with some modicum of copypasta. It's going to happen just because of the nature of the PowerShell environment. Look at Microsoft's own cmdlets - you'll see evidence of it there too. The key is to minimize it.
Having 3 cmdlets that all take username & password (why not take a Credential object instead/as another option, BTW?) will result in copying & pasting those parameters in the function definition. You're not going to avoid that, and it's not necessarily a bad thing. You can create code snippets in most good editors (PowerShell ISE included) to automatically "generate" it for you if that makes it easier/faster.
I personally like to create intermediary functions that call my functions with specific parameters for things I do a lot of times. I manage these with a switch statement. This way, the backend driver does not change, and I have a nice interface I can give to others who want to use, but not develop on, the code I made.
function frontEnd {
call intermediary(typeA)
}
function intermediary (callType){
switch(callType){
case(typeA):
call backEnd(param1="get dns" param2="domain1" param3=True
case(typeB):
call backEnd(param1="add to dns" param2="domain" param3=False
case(other):
call backEnd(arg1, arg2, arg3)
}
Depending on what functionality you are looking for, this could help you. This is a very crude way of doing it, and I highly suggesting making it more robust and stable if you aren't going to be the only one using it.
So I am working on some IIS management scripts for a specific IIS Site setup exclusive to a product to complete tasks such as:
- Create Site
- Create App Pool
- Create Virtual directories
The problem, is I would like to keep separate scripts for each concern and reference them in a parent script. The parent script could be ran to do a full deployment/setup. Or you could run the individual scripts for a specific task. The problem is that they are interactive, so they will request for the user information relevant to completing the task.
I am not sure how to approach the problem where each script will have a script body that will acquire information from the user, yet if it is loaded into the parent script avoid that specific's scripts script body from prompting the user.
NOTE: I know I could put them into modules, and fire off the individual "Exported to the environment" functions, but this script is going to be moved around to the environment that needs setup, and having to manually put modules (psm1) files into the proper PowerShell module folders just to run the scripts is a route I am not particularly fond of.
I am new to scripting with Powershell, any thoughts or recommendations?
Possible Answer*
This might be (a) solution: but I found I could Import-Modules from the working directory and from there have access to those exported functions.
I am interested in any other suggestions as well.
They way I would address it would be to implement a param block at the top of each sub script that would collect the information it needs to run. If a sub script is run individually the param block would prompt the user for the data needed to run that individual script. This also allows the parent script to pass the data needed to run the subscripts as the parent script calls the sub script. The data needed can be hard coded in the parent script or prompted for or some mixture thereof. That way you can make the sub scripts run either silently or with user interaction. You get the user interaction for free from Powershell's parameter handling mechanism. In the subscripts add a parameter attribute to indicate that Powershell will request those particular parameter values from the user if they are not already provided by the calling script.
At the top of your sub scripts, use a parameter block to collected needed data.
param
(
[parameter(Mandatory=$true, HelpMessage="This is required, please enter a value.")]
[string] $SomeParameter
)
You can have a deploy.ps1 script which dot sources the individual scripts and then calls the necessary functions within them:
. $scriptDir\create-site.ps1
. $scriptDir\create-apppool.ps1
. $scriptDir\create-virtualdirectories.ps1
Prompt-Values
Create-Site -site test
Create-AppPool -pool test
Create-VirtualDirectories -vd test
In the individual functions, you can see if the values needed are passed in from the caller ( deploy.ps1 or the command line)
For example, create-site.ps1 will be like:
function Create-Site($site){
if(-not $site){
Prompt-Values
}
}
The ideal is to make the module take care of maintaining storing it's own settings, depending on distribution concerns of that module, and to make commands to help work with the settings.
I.e.
Write a Set-SiteInfo -Name -Pool -VirtualDirectory and have that store values in the registry or in the local directory of the module ($psScriptRoot), then have other commands in the module use this.
If the module is being put in a location where there's no file write access for low-rights users (i.e. a web site directory, or $psHome), then it's a notch better to store the values in the registry.
Hope this Helps