Unleash the true potential of PowerShell with tab completion. In this article, we delve into the world of PowerShell tab completion and explore its features, tips, and tricks. Learn how to leverage tab completion to quickly and accurately complete commands, navigate through parameters, access variable values, and discover hidden options. Enhance your PowerShell experience and become a more efficient and productive scripter.
Simple Introduction to ArgumentCompleters
Making a Value Scriptblock
In PowerShell, a script block is a collection of statements enclosed in curly braces ({}) that can be treated as a single unit and executed. A value script block is a type of script block that is commonly used in PowerShell tab completion to provide dynamic values for tab completion options.
To create a value script block for PowerShell tab completion, you can follow these steps:
- Define the script block: Start by defining the script block that will generate the dynamic values for tab completion. The script block can contain any valid PowerShell code.
$scriptBlock = {
# PowerShell code to generate dynamic values
# ...
}
- Define the tab completion attribute: Next, you need to define the tab completion attribute for the parameter or argument that will use the value script block. This attribute specifies the script block to be used for tab completion.
[Parameter(Position = 0)]
[ArgumentCompleter($scriptBlock)]
param(
# Parameter or argument declaration
# ...
)
- Implement the dynamic value logic: Inside the script block, you can implement the logic to generate the dynamic values based on the current input or any other relevant factors. This can involve querying data sources, performing calculations, or any other operations.
$scriptBlock = {
# PowerShell code to generate dynamic values
# ...
# Return the generated values as an array
$dynamicValues
}
- Use the tab completion: When the user interacts with the PowerShell command or script and triggers tab completion for the parameter or argument with the value script block, PowerShell will invoke the script block and retrieve the dynamic values. These values will be displayed as tab completion options for the user to choose from.
By using a value script block for PowerShell tab completion, you can provide dynamic and context-sensitive values to enhance the user experience and make your scripts more interactive.
Dynamic Parameter Values and ArgumentCompleters
In PowerShell, dynamic parameter values and ArgumentCompleters are used to provide users with more interactive and context-sensitive command-line experiences. They allow for the dynamic generation of parameter values or completion options based on specific conditions or input.
Dynamic Parameter Values
Dynamic parameter values are used when the available values for a parameter depend on other factors, such as the current state of the system or previous user input. By dynamically generating parameter values, you can provide a more flexible and user-friendly command-line interface.
To implement dynamic parameter values, you can use parameter attributes such as the [ValidateSet] attribute or script blocks. The [ValidateSet] attribute restricts the valid values for a parameter, while script blocks allow you to generate values dynamically based on the provided logic.
ArgumentCompleters
ArgumentCompleters are used to provide dynamic completion options for command-line arguments. They allow for the generation of valid input choices based on specific conditions or data sources. ArgumentCompleters are particularly useful for commands with complex or large sets of possible arguments, where manually typing the entire value is cumbersome or error-prone.
To use ArgumentCompleters, you can assign a script block or a custom class implementing the System.Management.Automation.IArgumentCompleter interface to the parameter or argument that requires dynamic completion. The script block or custom class will be invoked to generate the available completion options based on the current input.
By leveraging dynamic parameter values and ArgumentCompleters, you can enhance the usability and efficiency of your PowerShell commands by providing users with relevant and context-aware input options.
Moving Parameter Values to Scriptblock
Positional Parameters and Scriptblock
In PowerShell, you can pass parameter values to a script block using positional parameters or by explicitly specifying the parameter names within the script block.
Positional Parameters: When using positional parameters, the values are passed to the script block in the order they are defined. The script block can access these values using the automatic variables $args[0], $args[1], and so on. For example:
$scriptBlock = { param($param1, $param2) Write-Host "Parameter 1: $param1, Parameter 2: $param2" }
& $scriptBlock "Value 1" "Value 2"
In the above example, the script block defines two positional parameters, $param1 and $param2. When executing the script block, we pass the values “Value 1” and “Value 2” in the same order. The script block then uses these values to display the parameter values.
Specifying Parameter Names: Alternatively, you can explicitly specify the parameter names within the script block. This allows you to pass the parameter values by name, rather than relying on the order. For example:
$scriptBlock = { param($param1, $param2) Write-Host "Parameter 1: $param1, Parameter 2: $param2" }
& $scriptBlock -param1 "Value 1" -param2 "Value 2"
In this case, we use the -param1 and -param2 parameter names to pass the respective values to the script block. The order of the parameters no longer matters since they are explicitly named.
Using either positional parameters or named parameters within the script block allows you to pass values dynamically and access them within the script block based on your requirements.
Sending User-Provided Values to your Scriptblock
When passing user-provided values to a script block in PowerShell, you can use script block parameters or by using the $args automatic variable.
Script Block Parameters: One way to pass user-provided values is by defining script block parameters. You can specify the expected parameters in the script block definition and then pass the corresponding values when invoking the script block. For example:
$scriptBlock = { param($param1, $param2) Write-Host "Parameter 1: $param1, Parameter 2: $param2" }
$param1Value = Read-Host "Enter value for parameter 1"
$param2Value = Read-Host "Enter value for parameter 2"
& $scriptBlock -param1 $param1Value -param2 $param2Value
In the above example, the script block defines two parameters, $param1 and $param2. The user is prompted to enter values for these parameters using the Read-Host cmdlet. The script block is then invoked with the user-provided values.
Using $args: Another approach is to use the $args automatic variable within the script block. The $args variable holds an array of all the arguments passed to the script block, allowing you to access them directly. For example:
$scriptBlock = { Write-Host "Parameter 1: $($args[0]), Parameter 2: $($args[1])" }
$param1Value = Read-Host "Enter value for parameter 1"
$param2Value = Read-Host "Enter value for parameter 2"
& $scriptBlock $param1Value $param2Value
In this case, the script block uses $args[0] and $args[1] to access the user-provided values directly. The values are passed to the script block using positional arguments.
Both approaches allow you to pass user-provided values to a script block and use them as needed within the script block’s code. Choose the method that best fits your requirements and the desired level of parameterization.
Including PowerShell Tab Completion with Get-CimInstance CIM Classes
function Get-CimClassArgumentCompleter {
[CmdletBinding()]
param(
[Parameter(Mandatory = $true, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true)]
[string]$WordToComplete,
[Parameter(Mandatory = $true)]
[System.Management.Automation.CommandAst]$CommandAst,
[Parameter(Mandatory = $true)]
[System.Management.Automation.ParameterAst]$ParameterAst,
[Parameter(Mandatory = $true)]
[System.Management.Automation.CompletionContext]$CompletionContext
)
# Retrieve the CIM classes matching the partial class name
$classNames = Get-CimClass -ClassName $WordToComplete
if ($classNames) {
# Convert the class names to completion results
$completionResults = $classNames | ForEach-Object {
[System.Management.Automation.CompletionResult]::new($_.CimClassName, $_.CimClassName, 'ParameterValue', $_.CimClassName)
}
# Return the completion results
$completionResults
}
}
# Register the argument completer for the -ClassName parameter of Get-CimInstance
Register-ArgumentCompleter -CommandName 'Get-CimInstance' -ParameterName 'ClassName' -ScriptBlock { Get-CimClassArgumentCompleter }
In the above example, we define the Get-CimClassArgumentCompleter function, which takes the partial class name as input and retrieves the CIM classes that match the provided name. The function converts the class names into completion results.
We then use the Register-ArgumentCompleter cmdlet to register this argument completer function for the -ClassName parameter of the Get-CimInstance cmdlet.
Once you run this code, you will have tab completion support for the -ClassName parameter of the Get-CimInstance cmdlet, where you can start typing a partial class name, press Tab, and get a list of available CIM classes that match the partial name.
Congratulations! You’ve now become a tab completion wizard in PowerShell. With the knowledge and techniques covered in this article, you can navigate PowerShell with ease, save time, and minimize errors. Whether you’re a beginner or an experienced user, embracing tab completion will undoubtedly supercharge your productivity and streamline your scripting tasks. Embrace the power of tab completion and take your PowerShell skills to the next level.
