This function returns the built-in subdomain aliases for an account's main domain.
Note:
  This function retrieves data from the /var/cpanel/userdata/user/domain file, where user represents the cPanel account username and domain represents the domain. For this reason, actual output may not contain all of the returns that this document lists.
uapi --output=jsonpretty \ --user=username \ DomainInfo \ main_domain_builtin_subdomain_aliases
{- "apiversion": 3,
- "func": "main_domain_builtin_subdomain_aliases",
- "module": "DomainInfo",
- "result": {- "data": [- "mail",
- "www"
 ],
- "errors": null,
- "messages": null,
- "metadata": {- "transformed": 1
 },
- "status": 1,
- "warnings": null
 }
}