To download a single file from a repo, simply provide the repo_id and filename as follow:  
```bash
>>> huggingface-cli download gpt2 config.json
downloading https://huggingface.co/gpt2/resolve/main/config.json to /home/wauplin/.cache/huggingface/hub/tmpwrq8dm5o
(…)ingface.co/gpt2/resolve/main/config.json: 100%|██████████████████████████████████| 665/665 [00:00<00:00, 2.49MB/s]
/home/wauplin/.cache/huggingface/hub/models--gpt2/snapshots/11c5a3d5811f50298f278a704980280950aedb10/config.json
```  
The command will always print on the last line the path to the file on your local machine.