# Specify Output file name using ct.output.download

**URL:** <https://forum.ecmwf.int/t/specify-output-file-name-using-ct-output-download/1764>\
**Category:** Other - Software and tools\
**Tags:** c3s, toolbox\
**Created:** [8 November 2022 18:25 UTC](https://forum.ecmwf.int/t/specify-output-file-name-using-ct-output-download/1764 "2022-11-08T18:25:18Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Oleksandr\_Bobryshev](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/o/7feea3/32.png) [@Oleksandr\_Bobryshev](https://forum.ecmwf.int/u/Oleksandr_Bobryshev)\
**Post date:** [8 November 2022 18:25 UTC](https://forum.ecmwf.int/t/specify-output-file-name-using-ct-output-download/1764/1 "2022-11-08T18:25:18Z")

</div>

Dear all,

is there a possibility to specify the name for the output file (line 4 in the code below)?

```
import cdstoolbox as ct

@ct.application(title=‘Download data’)  
@ct.output.download() # I would like to specify the name of the output file here.  
def download\_application():  
data = ct.catalogue.retrieve(  
‘satellite-precipitation’,  
{  
‘variable’: ‘all’,  
‘time\_aggregation’: ‘monthly\_mean’,  
‘year’: ‘2010’,  
‘month’: [  
‘01’, ‘02’, ‘03’,  
‘04’, ‘05’, ‘06’,  
‘07’, ‘08’, ‘09’,  
‘10’, ‘11’, ‘12’,  
],  
}  
)  
return data
```

I don't understand the API documentation, please see the code below. Could you please give a bit more information about 'type' and 'format' variables?

```
def download(format=None) -> _T.Callable:
	type = 'xarray.core.dataarray.DataArray'
    return _specs.annotate(name='return', type=type, format=format)
```

```
Thank you.  
  
Best,  
Alex
```

```

```