> ## Documentation Index
> Fetch the complete documentation index at: https://docs.arc.cdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# arc:null

> Use arc:null to check that an attribute does not exist in the specified item.

export const siteNameShort = "Arc";

Use the `arc:null` keyword to check that an attribute does not exist in the specified item.

## Parameters

* **item**: The item to check. If not specified, the default item is used.
* **attr**: The name of the attribute to check.
* **action**: The action to perform if the expression evaluates to true. Allowed values: `break` or `continue`.

## Control Attributes

None

## Example

Define missing title attributes.

```xml theme={null}
<arc:call op="fileListDir" output="out">
  <arc:null attr="filename">
    <arc:set attr="title" value="Unnamed File"/>
    <arc:else>
      <arc:set attr="title" value="[filename]"/>
    </arc:else>
  </arc:null>
  <arc:push title="[title]">
  [out.file:*] 
  </arc:push>
</arc:call>
```

## See Also

* [arc:else](./op-arc-else): Create a block which is executed if the condition is not satisfied.