Yaml template validation issue with template Parameters

Question

I have parameter variables. how to refer to multiple ref variables in one line?
Parameter:
```
 s3Bucket:
    Type: String
    Description: -------
    Default: '...'
 s3Path:
     Type: String
     Description: -------
     Default: '...'
 libraryFile:
     Type: String
     Description: ------
     Default: '...'
```
S3Bucket: !Ref s3Bucket
S3Key: !Ref s3Path/libraryFile

S3Key is throwing validation error.

Accepted Answer

If I understand your question correctly, it's Fn::Sub that you're after. e.g:

```
S3Bucket: !Sub ${s3Bucket}/${s3Path}/${libraryFile}
```

Answer

Take a look at the [Fn::Join](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-join.html) function. You can build your full S3Key using this.

```
S3Key: !Join
  -- '/'
    - !Ref s3Path
    - !Ref libraryFile
```

Yaml template validation issue with template Parameters

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