Escaping Remote ENV in Interpolation

[delianides]

When using systemd on CoreOS, consider the following:

   - name: docker.service
      command: start
      content: |
        [Unit]
        After=flannel.service
        Wants=flannel.service
        Description=Docker Application Container Engine
        Documentation=http://docs.docker.io

        [Service]
        EnvironmentFile=/run/flannel/subnet.env
        ExecStartPre=/bin/mount --make-rprivate /
        ExecStart=/usr/bin/docker -d --bip=${FLANNEL_SUBNET} --mtu=${FLANNEL_MTU} -s=overlay -H fd://

        [Install]
        WantedBy=multi-user.target

If I place this in a heredoc (hashicorp/hcl#6) it fails because terraform tries to interpolate the FLANNEL environment variables. Is there anyway to escape those so terraform doesn't try to expand them?

[mitchellh]

Use a second dollar sign: $${FLANNEL_SUBNET}.

[mitchellh]

Use a second dollar sign: $${FLANNEL_SUBNET}.

[bitglue]

Maybe this could be documented somewhere? I don't see it in the configuration syntax or the interpolation syntax.

But also, it doesn't seem to work. While it does avoid the syntax error due to the invalid interpolation, it also puts a literal $$ in the resulting parsed string.

[bitglue]

Maybe this could be documented somewhere? I don't see it in the configuration syntax or the interpolation syntax.

But also, it doesn't seem to work. While it does avoid the syntax error due to the invalid interpolation, it also puts a literal $$ in the resulting parsed string.

[bentterp]

I ran into the same issue with an AWS policy as a heredoc as per the documentation:

policy = <<EOF

{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": [
"iam:_LoginProfile",
"iam:_AccessKey",
"iam:AccessKey"
],
"Resource": "arn:aws:iam::564070118781:user/$${aws:username}"
},

This results in the policydocument on AWS having double $'s - which of course doesn't work
Using single $ makes terraform try to interpolate, and fail

[bentterp]

I ran into the same issue with an AWS policy as a heredoc as per the documentation:

policy = <<EOF

{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": [
"iam:_LoginProfile",
"iam:_AccessKey",
"iam:AccessKey"
],
"Resource": "arn:aws:iam::564070118781:user/$${aws:username}"
},

This results in the policydocument on AWS having double $'s - which of course doesn't work
Using single $ makes terraform try to interpolate, and fail