Playing with syswrite

client.rb

require "drb/drb"

DRb.start_service

@screen = DRbObject.new_with_uri "druby://localhost:6789"

def write content
  @screen.write content
end

require "irb"
puts "Connected to screen"
puts "use write() method"
puts
puts "e.g. write \"Hello, world!\""
binding.irb

Playing with syswrite.md

Playing with syswrite

Run screen.rb

Run client.rb

Try it out

write "Hello"
write "\e[1G" # go to start of line
write "\e[0K" # clear line
write "\e[1A" # go up one

screen.rb

require "drb/drb"

class Screen
  def initialize output
    @output = output
  end

  def write content
    @output.syswrite content
  end
end

screen = Screen.new STDOUT

DRb.start_service "druby://localhost:6789", screen

puts "screen available @ druby://localhost:6789"
DRb.thread.join

typewriter.rb

require "drb/drb"

DRb.start_service

@screen = DRbObject.new_with_uri "druby://localhost:6789"

def write *contents
  contents.each { |content| @screen.write content }
end
def clear_screen
  @screen.clear
end

# 0   Header (real-time updates) (poll on every keystroke)
# 1
# 2   > prompt
# 3
# 4   $ last run comment
# 5   output here
# 6
# 7   $ the command before that
# 8   output here

clear_screen

write "[This is the header]\n"
write "\n"
write "> this is where I'm typing my command..."

# later, print older ones below.
# right now, only show last command results.
# [{ command: "str", output: "str" }, {}]
# command_results = []

def run command_string
  # re-write the `>` with the command, as if we typed it
  write_line "> #{command_string}"

  if @last_output_lines
    # if the output of a previous command is present, delete it
    go_down 2
    write_line "$ "
    @last_output_lines.times { go_down; clear_line }
    @last_output_lines.times { go_up }
    go_up 2
  else
    # else, this is the first `run` - let's add the $ line below for output
    go_down 2
    write "$ \n"
    write "\n"
    go_up 4
  end

  # copy command from > to $
  go_down 2
  write_line "$ #{command_string}"

  # clear the prompt (after drawing the command down below)
  go_up 2
  write_line "> "

  # get the output (stdout only), hoping it doesn't blow up
  output = `#{command_string} 2>&1`

  # print the output on the line below $ command
  go_down 3
  write output

  # now the cursor is output lines length further down
  # put the cursor back on the prompt line
  go_up output.lines.length + 3
  @last_output_lines = output.lines.length
end

def go_down lines = 1
  write "\e[#{lines}E"
end

def go_up lines = 1
  write "\e[#{lines}A"
end

def clear_line
  write "\e[1G\e[0K"
end

def write_line line
  clear_line
  write line
end

require "irb"
puts "Connected to screen"
puts "use write() method"
puts
puts "e.g. write \"Hello, world!\""
binding.irb