SSHEx

Simple SSH helpers for Elixir.

Library to unify helpers already used on several applications. It uses low level Erlang ssh library.

The only purpose of these helpers is to avoid repetitive patterns seen when working with SSH from Elixir. It doesn't mean to hide anything from the venerable code underneath. If there's an ugly crash from :ssh it will come back as {:error, reason}.

Use

Just add {:sshex, "2.0.0"} to your deps on mix.exs.

Then assuming :ssh application is already started (hence it is listed on deps), you should acquire an SSH connection using :ssh.connect/4 like this:

    {:ok, conn} = :ssh.connect('123.123.123.123', 22,
                    [ {:user,'myuser'}, {:silently_accept_hosts, true} ], 5000)

Then you can use the acquired conn with the cmd!/4 helper like this:

    SSHEx.cmd! conn, 'mkdir -p /path/to/newdir'
    res = SSHEx.cmd! conn, 'ls /some/path'

This is meant to run commands which you don't care about the return code. cmd!/3 will return the output of the command only, and will raise any errors. If you want to check the status code, and control errors too, you can use run/3 like this:

{:ok, _, 0} = SSHEx.run conn, 'rm -fr /something/to/delete'
{:ok, res, 0} = SSHEx.run conn, 'ls /some/path'
{:error, reason} = SSHEx.run failing_conn, 'ls /some/path'

You can pass the option :separate_streams to get separated stdout and stderr. Like this:

{:ok, stdout, stderr, 2} = SSHEx.run conn, 'ls /nonexisting/path', separate_streams: true

You will be reusing the same SSH connection all over.

Streaming

You can use SSHEx to run some command and create a Stream, so you can lazily process an arbitrarily long output as it arrives. Internally Stream.resource/3 is used to create the Stream, and every response from :ssh is emitted so it can be easily matched with a simple case.

You just have to use stream/3 like this:

str = SSHEx.stream conn, 'somecommand'

Stream.each(str, fn(x)->
  case x do
    {:stdout,row}    -> process_stdout(row)
    {:stderr,row}    -> process_stderr(row)
    {:status,status} -> process_exit_status(status)
    {:error,reason}  -> process_error(row)
  end
end)

Alternative keys

To use alternative keys you should save them somewhere on disk and then set the :user_dir option for :ssh.connect/4. See ssh library docs for more options.

TODOs

• Add tunnelling helpers *

Changelog

2.0.0

Backwards incompatible changes:

• Remove every raise, get clean controlled {:error, reason} responses
• Put every optional parameter under a unique Keyword list

1.3.1

• Fix Elixir version requested. Use >= 1.0 now.

1.3

• Support streaming via stream/3
• Stop using global mocks (i.e. :meck)

1.2

• Uniform raise behaviour on :ssh errors.
• Document and test :ssh error handling

1.1

• Add support for separate stdout/stderr responses.

1.0

• Initial release