| Attribute | Type | Description | Required | 
        
          | name | string | The name of the environment variable. | True | 
        
          | dir | directory | The value for a directory-based environment variable. NAnt will convert it to an absolute path. | False | 
        
          | file | file | The value for a file-based environment variable. NAnt will convert it to an absolute filename. | False | 
        
          | if | bool | Indicates if the environment variable should be passed to the external program. If true then the environment variable will be passed; otherwise, skipped. The default is true. | False | 
        
          | path | <path> | The value for a PATH like environment variable. You can use :or;as path separators and NAnt will convert it to the platform's local conventions. | False | 
        
          | unless | bool | Indicates if the environment variable should not be passed to the external program. If false then the environment variable will be passed; otherwise, skipped. The default is false. | False | 
        
          | value | string | The literal value for the environment variable. | False |