Output to console while preserving user input in ruby

console, input, ruby

Solution

The two important parts of my proposal are: 1. system("stty raw -echo") # to instantly get any typed character in combination with 2. using STDIN.getc with a string-var serving as an input-buffer to reprint the user input.

Pressing 9 (& boolean variable incoming_message) is used for ultra-simple simulation for your server-messages. (Being more realistic would bloat the example without adding much, since you have to adapt the idea for your scenario anyway.)

Press x for exit.

Sample output:

$ ruby simultaneous_input_and_output.rb
Hello World!9
The incoming message is: true
Hello World!9x

You entered:
Hello World!9x
End!

#!/usr/bin/ruby

$input_buffer = "";  
incoming_message = false

begin  
  system("stty raw -echo")  

  begin   
    str = STDIN.getc  
    print str.chr  

    $input_buffer = $input_buffer + str.chr  
    if str.chr == '9'  
      incoming_message = true  
    end  
    if incoming_message   
      puts "\nThe incoming message is: " + incoming_message.to_s  
      print $input_buffer  
      incoming_message = false  
    end  
  end while (str.chr != 'x')  
ensure  
  system("stty -raw echo")  
end  

puts "\n\nYou entered:"   
puts $input_buffer  
puts "End!"

P.S.: for system("stty raw -echo") see (User Jay) How to get a single character without pressing enter?

Problem

I have a ruby script that is simultaneously and asynchronously receiving and displaying messages from a server, and allowing user input on the console. When a message is received, it is currently being written in the middle of what the user is typing. The input itself isn't garbled, but it looks horrible. Ideally, it would save the users current input, output the message, and then restore the input on the next line. I've done this in c by intercepting every key stroke, but all I remember is that it was a major hassle. I'm fairly new to ruby, so I'm not sure if there is a good way to do this, or how to do it. Example: User is typing `>abcde`, and message `hello` comes in, and user types `fgh` after. The console would now show: ``` >abcdehellofgh ``` and user can continue typing at the end. I would like it to show: ``` hello >abcdefgh ```

Original source