Since it’s an erlang module, I expect that you will need to use erlang strings (that in Elixir are charlists - note the single quotes) and therefore, using your example:

:ftp.open('my.ftps.server', [what: 'options', go: 'here?']

Update: For anyone else who may have this problem in the future @NobbZ answer worked for me. Here is a code snippet

host = 'the.host.address'
{username, password} = {'myUserName', 'S3cr3t5'}
directory = '/the/directory/which/has/the/file/I/want'
file_name = 'file_to_download.txt'

{:ok, ftp_client} = :ftp.open(host, [tls: []])
:ftp.user(ftp_client, username, password)
:ftp.cd(ftp_client, directory)
{:ok, file_content} = :ftp.recv_bin(ftp_client, file_name)

Well spot! Thank you.

Yeah, those huge nested typespecs that the erlang documentation uses can be confusing at times… Especially if mentioned types are sometimes only locally scoped and sometimes global and sometimes remote, and linking is very bad between them. Its often manually drilling and hunting them down .

Thanks for the code monkey. Three years later and still of value!