Allow not to disable echo when using pty mode

[SteffenDE]

Hi there,

I'm currently working on something that uses erlexec to run interactive terminal sessions. For this, I needed a way to skip disabling the echo mode when using a pseudo terminal. I'm not quite sure if this is the right way to do this or if there should be even more control over the pty settings, but this works well for me and I sadly do have neither the Erlang nor the C++ experience to implement something more sophisticated than this.

Also, I noticed that some tests were failing for me until I changed the line io_lib:printable_list(Cmd) to io_lib:printable_unicode_list(Cmd) that is completely unrelated to my changes.

What are your thoughts on this?

[saleyn]

This sounds good. Though I would prefer to rename the new parameter to pty_echo = true | false with false being the default. Do you mind updating the PR?

[SteffenDE]

Yes you're right. I initially called it pty_echo, but then thought that actually we're not "enabling" echo but rather not disable it in the first place. My naming choice was rather awkward still. I don't know if there are systems where echo has to be manually enabled, therefore the pty_echo name being misleading. Maybe there could be room for improvement by allowing something like:
{pty_modes, [{echo, 1}, {echoe, 1}, {echok, 1}]}, see also https://www.erlang.org/doc/man/ssh_connection.html#type-pty_ch_msg and https://datatracker.ietf.org/doc/html/rfc4254#section-8

[saleyn]

I agree that it would be great to support all modes mentioned in section-8 of the RFC4254.

[saleyn]

Thank you for your contribution!