How to get Latest Published version of a Lambda Function in AWS CLI

Question

How to get Latest Published version of a Lambda Function? Apart from $LATEST, how can I get the result as "5"

$ aws lambda list-versions-by-function --function-name My_Lambda_Function --query 'Versions[*][Version, FunctionArn]' --output json
[
    [
        "$LATEST",
        "arn:aws:lambda:us-east-2:123456789000:function:My_Lambda_Function:$LATEST"
    ],
    [
        "1",
        "arn:aws:lambda:us-east-2:123456789000:function:My_Lambda_Function:1"
    ],
    [
        "2",
        "arn:aws:lambda:us-east-2:123456789000:function:My_Lambda_Function:2"
    ],
    [
        "3",
        "arn:aws:lambda:us-east-2:123456789000:function:My_Lambda_Function:3"
    ],
    [
        "4",
        "arn:aws:lambda:us-east-2:123456789000:function:My_Lambda_Function:4"
    ],
    [
        "5",
        "arn:aws:lambda:us-east-2:123456789000:function:My_Lambda_Function:5"
    ]
]

Answer 1

I found this thread on GitHub insightful, you can get the maximum non-$LATEST item a few ways but only one of them is correct:

Wrong way, this command will be correct only as far as version 9 because it will string-compare the versions and decide that "9" is greater than "10":

aws lambda list-versions-by-function --function-name my_lambda \
  --query "max_by(Versions, &Version)"

Wrong way, this command will be correct only as far as version 50 (or whatever the page size is) because it will only filter the results that are returned in the first page.

aws lambda list-versions-by-function --function-name my_lambda \
  --query "Versions[-1]"

Wrong way, this command will consider all the results before filtering them, but still assumes that they will be in proper order

aws lambda list-versions-by-function --function-name my_lambda \
  --no-paginate \
  --query "Versions[-1]"

Wrong way, this command looks right for sorting purposes but will choke on to_number("$LATEST") returning null.

aws lambda list-versions-by-function --function-name my_lambda \
  --no-paginate \
  --query "max_by(Versions, &to_number(Version))" 

Wrong way, this command looks right for sorting purposes but (on my machine) doesn't accept the literal 0.

aws lambda list-versions-by-function --function-name my_lambda \
  --no-paginate \
  --query "max_by(Versions, &to_number(Version) || '0')"

Right way, this command will fetch all the all the results before considering them, and works around the issue of numeric literals by converting to a number twice.

aws lambda list-versions-by-function --function-name my_lambda \
  --no-paginate \
  --query "max_by(Versions, &to_number(to_number(Version) || '0'))"