Ssh_client_channel trapping exits

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I have an ssh_cli handler that implements the ssh_server_channel behaviour, albeit written in Elixir, not Erlang. On receipt of the pty message it looks up the capabilities of the terminal by issuing:

System.cmd("infocmp", ["-1", term_name], stderr_to_stdout: true)

It does some handling of the successful output from this command, returns from handle_ssh_msg/2 and then … exits - the client is immediately disconnected from their ssh session :slightly_frowning_face:

It took me a little while to work out what was going on but I think it’s this:

  • ssh_client_channel traps exits
  • System.cmd/3 does not handle its port’s EXIT message in its selective receive
  • The EXIT message is then handled by the ssh_client_handler - it hands it off back to my callback module.
  • My callback module doesn’t deal with this message
  • The ssh_client_handler has explicit logic for catching function clauses that don’t deal with the EXIT message, wherein it closes the connection.

I could handle the EXIT message in handle_msg/2, but that doesn’t seem quite right because I don’t know anything about the port itself - its all hidden behind System.cmd/3.

Is the better thing to do here just to manage a port myself and, knowing that the hosting process is trapping exits, handle the normal EXIT message and throw it away?

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