I write this function

```
def docker_images(image_name,image_tag){

def curl_image_exists_status_code =

    curl_image_exists_status_code=sh (
    script:""" docker login -u XXXXX -p $$$$$$  2> /dev/null 1>/dev/null
    docker pull XXXXX/'${image_name}':'${image_tag}' > /dev/null && echo "success" || echo 'failed' 
    """,  returnStdout: true)
    echo "${curl_image_exists_status_code}"
    return (curl_image_exists_status_code == 'success')?true: false
    }

```

but the output is

> 
> success
> 
> 
> null
> 
> 
> 

and the last line returns `false`
the output of `curl_image_exists_status_code` should be success and the last line should return true
but why it is not working?