How to shut down dedicated server 'Cave'?

[Nagatoro]

I use this guide to start my server, with the code below

run_shared=(./dontstarve_dedicated_server_nullrenderer_x64)
run_shared+=(-console)
run_shared+=(-cluster "$cluster_name")
run_shared+=(-monitor_parent_process $$)

"${run_shared[@]}" -shard Caves  | sed 's/^/Caves:  /' &
"${run_shared[@]}" -shard Master | sed 's/^/Master: /'

Then I use the command to shut down 'Master'

c_shutdown()

But I find 'Cave' is still running

ps aux | grep "dontstarve_dedicated_server_nullrenderer_x64"
ubuntu      3767  0.0  0.9 586656 62072 pts/3    Tl   22:44   0:00 ./dontstarve_dedicated_server_nullrenderer_x64 -console -cluster MyDediServer -monitor_parent_process 3429 -shard Caves
ubuntu      4090  0.0  0.0   9740  2304 pts/3    R+   22:56   0:00 grep --color=auto dontstarve_dedicated_server_nullrenderer_x64

How can I shut down the 'Cave' gracefully without losing the data?

Thanks!