class Net::SSH::Connection::Channel

Instantiates a new channel on the given connection, of the given type, and with the given id. If a block is given, it will be remembered until the channel is confirmed open by the server, and will be invoked at that time (see do_open_confirmation).

This also sets the default maximum packet size and maximum window size.

# File lib/net/ssh/connection/channel.rb, line 113
def initialize(connection, type, local_id, max_pkt_size = 0x8000, max_win_size = 0x20000, &on_confirm_open)
  self.logger = connection.logger
    
  @connection = connection
  @type       = type
  @local_id   = local_id
    
  @local_maximum_packet_size = max_pkt_size
  @local_window_size = @local_maximum_window_size = max_win_size
    
  @on_confirm_open = on_confirm_open
    
  @output = Buffer.new
    
  @properties = {}
    
  @pending_requests = []
  @on_open_failed = @on_data = @on_extended_data = @on_process = @on_close = @on_eof = nil
  @on_request = {}
  @closing = @eof = @sent_eof = @local_closed = @remote_closed = false
end

A shortcut for accessing properties of the channel (see properties).

# File lib/net/ssh/connection/channel.rb, line 136
def [](name)
  @properties[name]
end

A shortcut for setting properties of the channel (see properties).

# File lib/net/ssh/connection/channel.rb, line 141
def []=(name, value)
  @properties[name] = value
end

Returns true if the channel exists in the channel list of the session, and false otherwise. This can be used to determine whether a channel has been closed or not.

ssh.loop { channel.active? }

# File lib/net/ssh/connection/channel.rb, line 262
def active?
  connection.channels.key?(local_id)
end

Requests that the channel be closed. It only marks the channel to be closed the CHANNEL_CLOSE message will be sent from event loop

# File lib/net/ssh/connection/channel.rb, line 299
def close
  return if @closing
  @closing = true
end

True if close() has been called; NOTE: if the channel has data waiting to be sent then the channel will close after all the data is sent. See closed?() to determine if we have actually sent CHANNEL_CLOSE to server. This may be true for awhile before closed? returns true if we are still sending buffered output to server.

# File lib/net/ssh/connection/channel.rb, line 280
def closing?
  @closing
end

Invokes the on_close callback when the server closes a channel. The channel is the only argument.

# File lib/net/ssh/connection/channel.rb, line 609
def do_close
  @on_close.call(self) if @on_close
end

Invokes the on_eof callback when the server indicates that no further data is forthcoming. The callback is invoked with the channel as the argument.

# File lib/net/ssh/connection/channel.rb, line 603
def do_eof
  @on_eof.call(self) if @on_eof
end

Invokes the on_extended_data callback when the server sends extended data to the channel. This will reduce the available window size on the local end. The callback is invoked with the channel, type, and data.

# File lib/net/ssh/connection/channel.rb, line 595
def do_extended_data(type, data)
  update_local_window_size(data.length)
  @on_extended_data.call(self, type, data) if @on_extended_data
end

Invokes the next pending request callback with false as the second argument.

# File lib/net/ssh/connection/channel.rb, line 615
def do_failure
  if callback = pending_requests.shift
    callback.call(self, false)
  else
    error { "channel failure received with no pending request to handle it (bug?)" }
  end
end

Invoked when the server failed to open the channel. If an on_open_failed callback was specified, it will be invoked with the channel, reason code, and description as arguments. Otherwise, a ChannelOpenFailed exception will be raised.

# File lib/net/ssh/connection/channel.rb, line 540
def do_open_failed(reason_code, description)
  if @on_open_failed
    @on_open_failed.call(self, reason_code, description)
  else
    raise ChannelOpenFailed.new(reason_code, description)
  end
end

Invokes the next pending request callback with true as the second argument.

# File lib/net/ssh/connection/channel.rb, line 625
def do_success
  if callback = pending_requests.shift
    callback.call(self, true)
  else
    error { "channel success received with no pending request to handle it (bug?)" }
  end
end

Syntactic sugar for setting an environment variable in the remote process' environment. Note that for security reasons, the server may refuse to set certain environment variables, or all, at the server's discretion. If you are connecting to an OpenSSH server, you will need to update the AcceptEnv setting in the sshd_config to include the environment variables you want to send.

channel.env "PATH", "/usr/local/bin"

# File lib/net/ssh/connection/channel.rb, line 190
def env(variable_name, variable_value, &block)
  send_channel_request("env", :string, variable_name, :string, variable_value, &block)
end

Tells the remote end of the channel that no more data is forthcoming from this end of the channel. The remote end may still send data. The CHANNEL_EOF packet will be sent once the output buffer is empty.

# File lib/net/ssh/connection/channel.rb, line 314
def eof!
  return if eof?
  @eof = true
end

Returns true if the local end of the channel has declared that no more data is forthcoming (see eof!). Trying to send data via send_data when this is true will result in an exception being raised.

# File lib/net/ssh/connection/channel.rb, line 307
def eof?
  @eof
end

Syntactic sugar for executing a command. Sends a channel request asking that the given command be invoked. If the block is given, it will be called when the server responds. The first parameter will be the channel, and the second will be true or false, indicating whether the request succeeded or not. In this case, success means that the command is being executed, not that it has completed, and failure means that the command altogether failed to be executed.

channel.exec "ls -l /home" do |ch, success|
  if success
    puts "command has begun executing..."
    # this is a good place to hang callbacks like #on_data...
  else
    puts "alas! the command could not be invoked!"
  end
end

# File lib/net/ssh/connection/channel.rb, line 161
def exec(command, &block)
  send_channel_request("exec", :string, command, &block)
end

True if we have sent CHANNEL_CLOSE to the remote server.

# File lib/net/ssh/connection/channel.rb, line 285
def local_closed?
  @local_closed
end

Registers a callback to be invoked when the server acknowledges that a channel is closed. This is invoked with the channel as the sole argument.

channel.on_close do |ch|
  puts "remote end is closing!"
end

# File lib/net/ssh/connection/channel.rb, line 401
def on_close(&block)
  old, @on_close = @on_close, block
  old
end

Registers a callback to be invoked when data packets are received by the channel. The callback is called with the channel as the first argument, and the data as the second.

channel.on_data do |ch, data|
  puts "got data: #{data.inspect}"
end

Data received this way is typically the data written by the remote process to its stdout stream.

# File lib/net/ssh/connection/channel.rb, line 348
def on_data(&block)
  old, @on_data = @on_data, block
  old
end

Registers a callback to be invoked when the server indicates that no more data will be sent to the channel (although the channel can still send data to the server). The channel is the sole argument to the callback.

channel.on_eof do |ch|
  puts "remote end is done sending data"
end

# File lib/net/ssh/connection/channel.rb, line 413
def on_eof(&block)
  old, @on_eof = @on_eof, block
  old
end

Registers a callback to be invoked when extended data packets are received by the channel. The callback is called with the channel as the first argument, the data type (as an integer) as the second, and the data as the third. Extended data is almost exclusively used to send stderr data (type == 1). Other extended data types are not defined by the SSH protocol.

channel.on_extended_data do |ch, type, data|
  puts "got stderr: #{data.inspect}"
end

# File lib/net/ssh/connection/channel.rb, line 363
def on_extended_data(&block)
  old, @on_extended_data = @on_extended_data, block
  old
end

Registers a callback to be invoked when the server was unable to open the requested channel. The channel itself will be passed to the block, along with the integer “reason code” for the failure, and a textual description of the failure from the server.

channel = session.open_channel do |ch|
  # ..
end

channel.on_open_failed { |ch, code, desc| ... }

# File lib/net/ssh/connection/channel.rb, line 428
def on_open_failed(&block)
  old, @on_open_failed = @on_open_failed, block
  old
end

Registers a callback to be invoked for each pass of the event loop for this channel. There are no guarantees on timeliness in the event loop, but it will be called roughly once for each packet received by the connection (not the channel). This callback is invoked with the channel as the sole argument.

Here's an example that accumulates the channel data into a variable on the channel itself, and displays individual lines in the input one at a time when the channel is processed:

channel[:data] = ""

channel.on_data do |ch, data|
  channel[:data] << data
end

channel.on_process do |ch|
  if channel[:data] =~ /^.*?\n/
    puts $&
    channel[:data] = $'
  end
end

# File lib/net/ssh/connection/channel.rb, line 390
def on_process(&block)
  old, @on_process = @on_process, block
  old
end

Registers a callback to be invoked when a channel request of the given type is received. The callback will receive the channel as the first argument, and the associated (unparsed) data as the second. The data will be a Net::SSH::Buffer that you will need to parse, yourself, according to the kind of request you are watching.

By default, if the request wants a reply, Net::SSH will send a CHANNEL_SUCCESS response for any request that was handled by a registered callback, and CHANNEL_FAILURE for any that wasn't, but if you want your registered callback to result in a CHANNEL_FAILURE response, just raise Net::SSH::ChannelRequestFailed.

Some common channel requests that your programs might want to listen for are:

• “exit-status” : the exit status of the remote process will be reported as a long integer in the data buffer, which you can grab via data.read_long.

• “exit-signal” : if the remote process died as a result of a signal being sent to it, the signal will be reported as a string in the data, via data.read_string. (Not all SSH servers support this channel request type.)

  channel.on_request "exit-status" do |ch, data|
    puts "process terminated with exit status: #{data.read_long}"
  end
  

# File lib/net/ssh/connection/channel.rb, line 459
def on_request(type, &block)
  old, @on_request[type] = @on_request[type], block
  old
end

If an on_process handler has been set up, this will cause it to be invoked (passing the channel itself as an argument). It also causes all pending output to be enqueued as CHANNEL_DATA packets (see enqueue_pending_output).

# File lib/net/ssh/connection/channel.rb, line 322
def process
  @on_process.call(self) if @on_process
  enqueue_pending_output
    
  if @eof and not @sent_eof and output.empty? and remote_id and not @local_closed
    connection.send_message(Buffer.from(:byte, CHANNEL_EOF, :long, remote_id))
    @sent_eof = true
  end
    
  if @closing and not @local_closed and output.empty? and remote_id
    connection.send_message(Buffer.from(:byte, CHANNEL_CLOSE, :long, remote_id))
    @local_closed = true
    connection.cleanup_channel(self)
  end
end

Requests that a pseudo-tty (or “pty”) be made available for this channel. This is useful when you want to invoke and interact with some kind of screen-based program (e.g., vim, or some menuing system).

Note, that without a pty some programs (e.g. sudo, or subversion) on some systems, will not be able to run interactively, and will error instead of prompt if they ever need some user interaction.

Note, too, that when a pty is requested, user's shell configuration scripts (.bashrc and such) are not run by default, whereas they are run when a pty is not present.

channel.request_pty do |ch, success|
  if success
    puts "pty successfully obtained"
  else
    puts "could not obtain pty"
  end
end

# File lib/net/ssh/connection/channel.rb, line 221
def request_pty(opts={}, &block)
  extra = opts.keys - VALID_PTY_OPTIONS.keys
  raise ArgumentError, "invalid option(s) to request_pty: #{extra.inspect}" if extra.any?
    
  opts = VALID_PTY_OPTIONS.merge(opts)
    
  modes = opts[:modes].inject(Buffer.new) do |memo, (mode, data)|
    memo.write_byte(mode).write_long(data)
  end
  # mark the end of the mode opcode list with a 0 byte
  modes.write_byte(0)
    
  send_channel_request("pty-req", :string, opts[:term],
    :long, opts[:chars_wide], :long, opts[:chars_high],
    :long, opts[:pixels_wide], :long, opts[:pixels_high],
    :string, modes.to_s, &block)
end

Sends a new channel request with the given name. The extra data parameter must either be empty, or consist of an even number of arguments. See Net::SSH::Buffer.from for a description of their format. If a block is given, it is registered as a callback for a pending request, and the packet will be flagged so that the server knows a reply is required. If no block is given, the server will send no response to this request. Responses, where required, will cause the callback to be invoked with the channel as the first argument, and either true or false as the second, depending on whether the request succeeded or not. The meaning of “success” and “failure” in this context is dependent on the specific request that was sent.

channel.send_channel_request "shell" do |ch, success|
  if success
    puts "user shell started successfully"
  else
    puts "could not start user shell"
  end
end

Most channel requests you'll want to send are already wrapped in more convenient helper methods (see exec and subsystem).

# File lib/net/ssh/connection/channel.rb, line 486
def send_channel_request(request_name, *data, &callback)
  info { "sending channel request #{request_name.inspect}" }
  fail "Channel open not yet confirmed, please call send_channel_request(or exec) from block of open_channel" unless remote_id
  msg = Buffer.from(:byte, CHANNEL_REQUEST,
    :long, remote_id, :string, request_name,
    :bool, !callback.nil?, *data)
  connection.send_message(msg)
  pending_requests << callback if callback
end

Sends data to the channel's remote endpoint. This usually has the effect of sending the given string to the remote process' stdin stream. Note that it does not immediately send the data across the channel, but instead merely appends the given data to the channel's output buffer, preparatory to being packaged up and sent out the next time the connection is accepting data. (A connection might not be accepting data if, for instance, it has filled its data window and has not yet been resized by the remote end-point.)

This will raise an exception if the channel has previously declared that no more data will be sent (see eof!).

channel.send_data("the password\n")

# File lib/net/ssh/connection/channel.rb, line 252
def send_data(data)
  raise EOFError, "cannot send data if channel has declared eof" if eof?
  output.append(data.to_s)
end

Syntactic sugar for requesting that a subsystem be started. Subsystems are a way for other protocols (like SFTP) to be run, using SSH as the transport. Generally, you'll never need to call this directly unless you are the implementor of something that consumes an SSH subsystem, like SFTP.

channel.subsystem("sftp") do |ch, success|
  if success
    puts "subsystem successfully started"
  else
    puts "subsystem could not be started"
  end
end

# File lib/net/ssh/connection/channel.rb, line 178
def subsystem(subsystem, &block)
  send_channel_request("subsystem", :string, subsystem, &block)
end

Runs the SSH event loop until the channel is no longer active. This is handy for blocking while you wait for some channel to finish.

channel.exec("grep ...") { ... }
channel.wait

# File lib/net/ssh/connection/channel.rb, line 271
def wait
  connection.loop { active? }
end