AWS Lambda function handler in PowerShell - AWS Lambda
Returning data

AWS Lambda function handler in PowerShell

When a Lambda function is invoked, the Lambda handler invokes the PowerShell script.

When the PowerShell script is invoked, the following variables are predefined:

  • $LambdaInput – A PSObject that contains the input to the handler. This input can be event data (published by an event source) or custom input that you provide, such as a string or any custom data object.

  • $LambdaContext – An Amazon.Lambda.Core.ILambdaContext object that you can use to access information about the current invocation—such as the name of the current function, the memory limit, execution time remaining, and logging.

For example, consider the following PowerShell example code.

#Requires -Modules @{ModuleName='AWSPowerShell.NetCore';ModuleVersion='3.3.618.0'}
Write-Host 'Function Name:' $LambdaContext.FunctionName

This script returns the FunctionName property that's obtained from the $LambdaContext variable.

Note

You're required to use the #Requires statement within your PowerShell scripts to indicate the modules that your scripts depend on. This statement performs two important tasks. 1) It communicates to other developers which modules the script uses, and 2) it identifies the dependent modules that AWS PowerShell tools need to package with the script, as part of the deployment. For more information about the #Requires statement in PowerShell, see About requires. For more information about PowerShell deployment packages, see Deploy PowerShell Lambda functions with .zip file archives.

When your PowerShell Lambda function uses the AWS PowerShell cmdlets, be sure to set a #Requires statement that references the AWSPowerShell.NetCore module, which supports PowerShell Core—and not the AWSPowerShell module, which only supports Windows PowerShell. Also, be sure to use version 3.3.270.0 or newer of AWSPowerShell.NetCore which optimizes the cmdlet import process. If you use an older version, you'll experience longer cold starts. For more information, see AWS Tools for PowerShell.

Returning data

Some Lambda invocations are meant to return data back to their caller. For example, if an invocation was in response to a web request coming from API Gateway, then our Lambda function needs to return back the response. For PowerShell Lambda, the last object that's added to the PowerShell pipeline is the return data from the Lambda invocation. If the object is a string, the data is returned as is. Otherwise the object is converted to JSON by using the ConvertTo-Json cmdlet.

For example, consider the following PowerShell statement, which adds $PSVersionTable to the PowerShell pipeline:

$PSVersionTable

After the PowerShell script is finished, the last object in the PowerShell pipeline is the return data for the Lambda function. $PSVersionTable is a PowerShell global variable that also provides information about the running environment.