This assumes you have already configured the aws command line tool. If not, check out my article on Getting Started with the AWS CLI.

The aws lambda list-functions command can be used to list the Lambda Functions you have created.

aws lambda list-functions

Something like this should be returned.

{
    "Functions": [
        {
            "TracingConfig": {
                "Mode": "PassThrough"
            },
            "Version": "$LATEST",
            "CodeSha256": "/ur2jHd199ldQbP+Y20sw3kIHhaWwnPY6CQvSwZ6Kco=",
            "FunctionName": "myfunction",
            "MemorySize": 128,
            "RevisionId": "741c094a-cff2-4cdb-a5b6-110a900e1a43",
            "CodeSize": 529507,
            "FunctionArn": "arn:aws:lambda:us-east-1:123456789012:function:myfunction",
            "Handler": "app.lambda_handler",
            "Role": "arn:aws:iam::123456789012:role/myfunction",
            "Timeout": 3,
            "LastModified": "2023-11-16T02:52:04.978+0000",
            "Runtime": "python3.9",
            "Description": ""
        }
    ]
}

You can:

• use the aws lambda update-function-configuration command to update your Lambda Function configuration
• use the aws lambda update-function-code command to update your Lambda Function code (this article)

Let's say you want to make a change to the function code. You could download a .zip file of the function from the AWS console. This should get you a zip file that contains the Lambda Function, something like this.

/path/to/lambda.zip

You can unzip the file.

unzip /path/to/lambda.zip -d /tmp/lambda

The extract should contain the contents of the .zip file, which is just a single lamba_function.py Python file in this example.

/tmp/lambda/lambda_function.py

Let's say you make a change to lambda_function.py. You would then create a zip file containing lambda_function.py.

zip lambda.zip /tmp/lambda/lambda_function.py

And then use the aws lambda update-function-code command to deploy the updated lambda.zip file.

]$ aws lambda update-function-code --function-name myfunction --zip-file fileb://lambda.zip
{
    "FunctionName": "myfunction",
    "FunctionArn": "arn:aws:lambda:us-east-1:123456789012:function:myfunction",
    "Runtime": "python3.11",
    "Role": "arn:aws:iam::123456789012:role/service-role/my-role",
    "Handler": "lambda_function.lambda_handler",
    "CodeSize": 1819,
    "Description": "",
    "Timeout": 3,
    "MemorySize": 128,
    "LastModified": "2023-12-15T02:54:28.000+0000",
    "CodeSha256": "5kHtMyCmdf31fSnR+BaNYhOn59MQp20WHvTJD9W6bCI=",
    "Version": "$LATEST",
    "TracingConfig": {
        "Mode": "PassThrough"
    },
    "RevisionId": "8bfcca82-e6e0-45e6-a198-67d5eba142d6",
    "Layers": [
        {
            "Arn": "arn:aws:lambda:us-east-1:myfunction:layer:mylayer:1",
            "CodeSize": 393575
        }
    ],
    "State": "Active",
    "LastUpdateStatus": "InProgress",
    "LastUpdateStatusReason": "The function is being created.",
    "LastUpdateStatusReasonCode": "Creating",
    "PackageType": "Zip",
    "Architectures": [
        "x86_64"
    ],
    "EphemeralStorage": {
        "Size": 512
    },
    "SnapStart": {
        "ApplyOn": "None",
        "OptimizationStatus": "Off"
    },
    "RuntimeVersionConfig": {
        "RuntimeVersionArn": "arn:aws:lambda:us-east-1::runtime:a3304f2b48f740276b97ad9c52a9cc36a0bd9b44fecf74d0f1416aafb74e92fc"
    }
}