Reserved Variables

Lambdas reserved environment variables

Lambda runtimes set several environment variables during initialization. The keys for these environment variables are reserved and cannot be set in your function configuration.

  • _HANDLER – The handler location configured on the function.
  • _X_AMZN_TRACE_ID – The X-Ray tracing header.
  • AWS_REGION – The AWS Region where the Lambda function is executed.
  • AWS_EXECUTION_ENV – The runtime identifier, prefixed by AWS_Lambda_—for example, AWS_Lambda_java8.
  • AWS_LAMBDA_FUNCTION_NAME – The name of the function.
  • AWS_LAMBDA_FUNCTION_MEMORY_SIZE – The amount of memory available to the function in MB.
  • AWS_LAMBDA_FUNCTION_VERSION – The version of the function being executed.
  • AWS_LAMBDA_INITIALIZATION_TYPE – The initialization type of the function, which is either on-demand or provisioned-concurrency. For information, see Configuring provisioned concurrency.
  • AWS_LAMBDA_LOG_GROUP_NAME , AWS_LAMBDA_LOG_STREAM_NAME – The name of the Amazon CloudWatch Logs group and stream for the function.
  • AWS_ACCESS_KEY_ID , AWS_SECRET_ACCESS_KEY, AWS_SESSION_TOKEN – The access keys obtained from the function's execution role.
  • AWS_LAMBDA_RUNTIME_API – (Custom runtime) The host and port of the runtime API.
  • LAMBDA_TASK_ROOT – The path to your Lambda function code.
  • LAMBDA_RUNTIME_DIR – The path to runtime libraries.
  • TZ – The environment's time zone (UTC). The execution environment uses NTP to synchronize the system clock.

More info

More information about Lambda environment variables found here.

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