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# `Fn::Join`
<a name="intrinsic-function-reference-join"></a>

The intrinsic function `Fn::Join` appends a set of values into a single value, separated by the specified delimiter. If a delimiter is the empty string, the set of values are concatenated with no delimiter.

## Declaration
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### JSON
<a name="intrinsic-function-reference-join-syntax.json"></a>

```
{ "Fn::Join" : [ "delimiter", [ comma-delimited list of values ] ] }
```

### YAML
<a name="intrinsic-function-reference-join-syntax.yaml"></a>

Syntax for the full function name:

```
Fn::Join: [ delimiter, [ comma-delimited list of values ] ]
```

Syntax for the short form:

```
!Join [ delimiter, [ comma-delimited list of values ] ]
```

## Parameters
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delimiter  
The value you want to occur between fragments. The delimiter will occur between fragments only. It won't terminate the final value.

ListOfValues  
The list of values you want combined.

## Return value
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The combined string.

## Examples
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### Join a simple string array
<a name="intrinsic-function-reference-join-example1"></a>

The following example returns: `"a:b:c"`.

#### JSON
<a name="intrinsic-function-reference-join-example1.json"></a>

```
"Fn::Join" : [ ":", [ "a", "b", "c" ] ]
```

#### YAML
<a name="intrinsic-function-reference-join-example1.yaml"></a>

```
!Join [ ":", [ a, b, c ] ]
```

### Join using the ref function with parameters
<a name="intrinsic-function-reference-join-example2"></a>

The following example uses `Fn::Join` to construct a string value. It uses the `Ref` function with the `AWS::Partition` parameter and the `AWS::AccountId` pseudo parameter.

#### JSON
<a name="intrinsic-function-reference-join-example2.json"></a>

```
{
  "Fn::Join": [
    "", [
      "arn:",
      {
        "Ref": "AWS::Partition"
      },
      ":s3:::elasticbeanstalk-*-",
      {
        "Ref": "AWS::AccountId"
      }
    ]
  ]
}
```

#### YAML
<a name="intrinsic-function-reference-join-example2.yaml"></a>

```
!Join
  - ''
  - - 'arn:'
    - !Ref AWS::Partition
    - ':s3:::elasticbeanstalk-*-'
    - !Ref AWS::AccountId
```

**Note**  
Also see the [`Fn::Sub`](intrinsic-function-reference-sub.md) function for similar functionality.

## Supported functions
<a name="intrinsic-function-reference-join-supportedfunctions"></a>

For the `Fn::Join` delimiter, you can't use any functions. You must specify a string value.

For the `Fn::Join` list of values, you can use the following functions:
+ `Fn::Base64`
+ `Fn::FindInMap`
+ `Fn::GetAtt`
+ `Fn::GetAZs`
+ `Fn::If`
+ `Fn::ImportValue`
+ `Fn::Join`
+ `Fn::Split`
+ `Fn::Select`
+ `Fn::Sub`
+ `Ref`