Converting a list to a string

[Andrew Langhorn]

Hi,

The aws_emr_cluster resource's ec2_attributes block accepts a subnet_id. I have a subnet per availability zone, and subnet_id accepts only one value.

In order to spin up a cluster in any of my available subnets, I was looking at using:

resource "random_shuffle" "az" {

  input = ["private-a", "private-b", "private-c"]

  result_count = 1

}

resource "aws_emr_cluster" "cluster" {

  ...

  ec2_attributes {

    ...

    subnet_id = "${random_shuffle.az.result}"

    ...

  }

}

This returns a list, rather than a string, which subnet_id expects. Is there a way to convert a list to a string?

Thanks,

Andrew

[David Adams]

I'm guessing that either:

    subnet_id = "${random_shuffle.az.result[0]}"

Or if not that, then:

    subnet_id = "${element(random_shuffle.az.result, 0)}"

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[Andrew Langhorn]

Ahhh, thanks. I'd previously tried element, but that didn't do the trick. But referring to the first item in the list that way worked a charm.

:)

[edw...@getdinghy.com]

The problem with the solution provided here is you're discarding any other items in the list.

Better to use the following function to convert the list directly to a string and keep everything.

https://www.terraform.io/docs/configuration/interpolation.html#join-delim-list-

e.g.

• ${join(",", var.ami_list)}