Using AWS Lambda with the AWS Command Line Interface

You can use the AWS Command Line Interface to manage functions and other AWS Lambda resources. The AWS CLI uses the AWS SDK for Python (Boto) to interact with the Lambda API. You can use it to learn about the API, and apply that knowledge in building applications that use Lambda with the AWS SDK.

In this tutorial, you manage and invoke Lambda functions with the AWS CLI. For more information, see What is the AWS CLI? in the AWS Command Line Interface User Guide.

Prerequisites

This tutorial assumes that you have some knowledge of basic Lambda operations and the Lambda console. If you haven't already, follow the instructions in Create a Lambda function with the console.

To complete the following steps, you need a command line terminal or shell to run commands. Commands and the expected output are listed in separate blocks:

aws --version

You should see the following output:

aws-cli/2.0.57 Python/3.7.4 Darwin/19.6.0 exe/x86_64

For long commands, an escape character (\) is used to split a command over multiple lines.

On Linux and macOS, use your preferred shell and package manager. On Windows 10, you can install the Windows Subsystem for Linux to get a Windows-integrated version of Ubuntu and Bash.

This tutorial uses the AWS Command Line Interface (AWS CLI) to call service API operations. To install the AWS CLI, see Installing the AWS CLI in the AWS Command Line Interface User Guide.

Create the execution role

Create the execution role that gives your function permission to access AWS resources. To create an execution role with the AWS CLI, use the create-role command.

aws iam create-role --role-name lambda-ex --assume-role-policy-document file://trust-policy.json

You should see the following output:

{
    "Role": {
        "Path": "/",
        "RoleName": "lambda-ex",
        "RoleId": "AROAQFOXMPL6TZ6ITKWND",
        "Arn": "arn:aws:iam::123456789012:role/lambda-ex",
        "CreateDate": "2020-01-17T23:19:12Z",
        "AssumeRolePolicyDocument": {
            "Version": "2012-10-17",
            "Statement": [
                {
                    "Effect": "Allow",
                    "Principal": {
                        "Service": "lambda.amazonaws.com"
                    },
                    "Action": "sts:AssumeRole"
                }
            ]
        }
    }
}

The trust-policy.json file is a JSON file in the current directory that defines the trust policy for the role. This trust policy allows Lambda to use the role's permissions by giving the service principal lambda.amazonaws.com permission to call the AWS Security Token Service AssumeRole action.

Example trust-policy.json

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": "lambda.amazonaws.com"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

You can also specify the trust policy inline. Requirements for escaping quotes in the JSON string vary depending on your shell.

aws iam create-role --role-name lambda-ex --assume-role-policy-document '{"Version": "2012-10-17","Statement": [{ "Effect": "Allow", "Principal": {"Service": "lambda.amazonaws.com"}, "Action": "sts:AssumeRole"}]}'

To add permissions to the role, use the attach-policy-to-role command. Start by adding the AWSLambdaBasicExecutionRole managed policy.

aws iam attach-role-policy --role-name lambda-ex --policy-arn arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole

The AWSLambdaBasicExecutionRole policy has the permissions that the function needs to write logs to CloudWatch Logs.

Create the function

The following example logs the values of environment variables and the event object.

Example index.js

exports.handler = async function(event, context) {
  console.log("ENVIRONMENT VARIABLES\n" + JSON.stringify(process.env, null, 2))
  console.log("EVENT\n" + JSON.stringify(event, null, 2))
  return context.logStreamName
}

To create the function

1. Copy the sample code into a file named index.js.

2. Create a deployment package.

   zip function.zip index.js

3. Create a Lambda function with the create-function command. Replace the highlighted text in the role ARN with your account ID.

   aws lambda create-function --function-name my-function \
   --zip-file fileb://function.zip --handler index.handler --runtime nodejs12.x \
   --role arn:aws:iam::123456789012:role/lambda-ex

   You should see the following output:

   {
       "FunctionName": "my-function",
       "FunctionArn": "arn:aws:lambda:us-east-2:123456789012:function:my-function",
       "Runtime": "nodejs12.x",
       "Role": "arn:aws:iam::123456789012:role/lambda-ex",
       "Handler": "index.handler",
       "CodeSha256": "FpFMvUhayLkOoVBpNuNiIVML/tuGv2iJQ7t0yWVTU8c=",
       "Version": "$LATEST",
       "TracingConfig": {
           "Mode": "PassThrough"
       },
       "RevisionId": "88ebe1e1-bfdf-4dc3-84de-3017268fa1ff",
       ...
   }

To get logs for an invocation from the command line, use the --log-type option. The response includes a LogResult field that contains up to 4 KB of base64-encoded logs from the invocation.

aws lambda invoke --function-name my-function out --log-type Tail

You should see the following output:

{
    "StatusCode": 200,
    "LogResult": "U1RBUlQgUmVxdWVzdElkOiA4N2QwNDRiOC1mMTU0LTExZTgtOGNkYS0yOTc0YzVlNGZiMjEgVmVyc2lvb...",
    "ExecutedVersion": "$LATEST"
}

You can use the base64 utility to decode the logs.

aws lambda invoke --function-name my-function out --log-type Tail \
--query 'LogResult' --output text |  base64 -d

You should see the following output:

START RequestId: 57f231fb-1730-4395-85cb-4f71bd2b87b8 Version: $LATEST
  "AWS_SESSION_TOKEN": "AgoJb3JpZ2luX2VjELj...", "_X_AMZN_TRACE_ID": "Root=1-5d02e5ca-f5792818b6fe8368e5b51d50;Parent=191db58857df8395;Sampled=0"",ask/lib:/opt/lib",
END RequestId: 57f231fb-1730-4395-85cb-4f71bd2b87b8
REPORT RequestId: 57f231fb-1730-4395-85cb-4f71bd2b87b8  Duration: 79.67 ms      Billed Duration: 80 ms         Memory Size: 128 MB     Max Memory Used: 73 MB

The base64 utility is available on Linux, macOS, and Ubuntu on Windows. For macOS, the command is base64 -D.

To get full log events from the command line, you can include the log stream name in the output of your function, as shown in the preceding example. The following example script invokes a function named my-function and downloads the last five log events.

Example get-logs.sh Script

This example requires that my-function returns a log stream ID.

#!/bin/bash
aws lambda invoke --function-name my-function --payload '{"key": "value"}' out
sed -i'' -e 's/"//g' out
sleep 15
aws logs get-log-events --log-group-name /aws/lambda/my-function --log-stream-name $(cat out) --limit 5

The script uses sed to remove quotes from the output file, and sleeps for 15 seconds to allow time for the logs to be available. The output includes the response from Lambda and the output from the get-log-events command.

./get-logs.sh

You should see the following output:

{
    "StatusCode": 200,
    "ExecutedVersion": "$LATEST"
}
{
    "events": [
        {
            "timestamp": 1559763003171,
            "message": "START RequestId: 4ce9340a-b765-490f-ad8a-02ab3415e2bf Version: $LATEST\n",
            "ingestionTime": 1559763003309
        },
        {
            "timestamp": 1559763003173,
            "message": "2019-06-05T19:30:03.173Z\t4ce9340a-b765-490f-ad8a-02ab3415e2bf\tINFO\tENVIRONMENT VARIABLES\r{\r  \"AWS_LAMBDA_FUNCTION_VERSION\": \"$LATEST\",\r ...",
            "ingestionTime": 1559763018353
        },
        {
            "timestamp": 1559763003173,
            "message": "2019-06-05T19:30:03.173Z\t4ce9340a-b765-490f-ad8a-02ab3415e2bf\tINFO\tEVENT\r{\r  \"key\": \"value\"\r}\n",
            "ingestionTime": 1559763018353
        },
        {
            "timestamp": 1559763003218,
            "message": "END RequestId: 4ce9340a-b765-490f-ad8a-02ab3415e2bf\n",
            "ingestionTime": 1559763018353
        },
        {
            "timestamp": 1559763003218,
            "message": "REPORT RequestId: 4ce9340a-b765-490f-ad8a-02ab3415e2bf\tDuration: 26.73 ms\tBilled Duration: 27 ms \tMemory Size: 128 MB\tMax Memory Used: 75 MB\t\n",
            "ingestionTime": 1559763018353
        }
    ],
    "nextForwardToken": "f/34783877304859518393868359594929986069206639495374241795",
    "nextBackwardToken": "b/34783877303811383369537420289090800615709599058929582080"
}

List the Lambda functions in your account

Run the following AWS CLI list-functions command to retrieve a list of functions that you have created.

aws lambda list-functions --max-items 10

You should see the following output:

{
    "Functions": [
        {
            "FunctionName": "cli",
            "FunctionArn": "arn:aws:lambda:us-east-2:123456789012:function:my-function",
            "Runtime": "nodejs12.x",
            "Role": "arn:aws:iam::123456789012:role/lambda-ex",
            "Handler": "index.handler",
            ...
        },
        {
            "FunctionName": "random-error",
            "FunctionArn": "arn:aws:lambda:us-east-2:123456789012:function:random-error",
            "Runtime": "nodejs12.x",
            "Role": "arn:aws:iam::123456789012:role/lambda-role",
            "Handler": "index.handler",
            ...
        },
        ...
      ],
      "NextToken": "eyJNYXJrZXIiOiBudWxsLCAiYm90b190cnVuY2F0ZV9hbW91bnQiOiAxMH0="
} 

In response, Lambda returns a list of up to 10 functions. If there are more functions you can retrieve, NextToken provides a marker you can use in the next list-functions request. The following list-functions AWS CLI command is an example that shows the --starting-token parameter.

aws lambda list-functions --max-items 10 --starting-token eyJNYXJrZXIiOiBudWxsLCAiYm90b190cnVuY2F0ZV9hbW91bnQiOiAxMH0=

Retrieve a Lambda function

The Lambda CLI get-function command returns Lambda function metadata and a presigned URL that you can use to download the function's deployment package.

aws lambda get-function --function-name my-function

You should see the following output:

{
    "Configuration": {
        "FunctionName": "my-function",
        "FunctionArn": "arn:aws:lambda:us-east-2:123456789012:function:my-function",
        "Runtime": "nodejs12.x",
        "Role": "arn:aws:iam::123456789012:role/lambda-ex",
        "CodeSha256": "FpFMvUhayLkOoVBpNuNiIVML/tuGv2iJQ7t0yWVTU8c=",
        "Version": "$LATEST",
        "TracingConfig": {
            "Mode": "PassThrough"
        },
        "RevisionId": "88ebe1e1-bfdf-4dc3-84de-3017268fa1ff",
        ...
    },
    "Code": {
        "RepositoryType": "S3",
        "Location": "https://awslambda-us-east-2-tasks.s3.us-east-2.amazonaws.com/snapshots/123456789012/my-function-4203078a-b7c9-4f35-..."
    }
}

For more information, see GetFunction.

Clean up

Run the following delete-function command to delete the my-function function.

aws lambda delete-function --function-name my-function

Delete the IAM role you created in the IAM console. For information about deleting a role, see Deleting roles or instance profiles in the IAM User Guide.