Ruby STDIN.getc does not read char on reception

Question

Seems that Ruby IO#getc wait until receiving a \n before returning the chars.

If you try running this script:

STDOUT.sync = true
STDIN.sync = true
while data = STDIN.getc
  STDOUT.puts "Char arrived"
end

It will return one "Char arrived" per char sent to stdin, but only after a \n has been sent.

Seems that all char are buffered even if I write STDIN.sync = true.

Does anyone knows how to make the script print "Char arrived" right after a char has been sent to STDIN ?

Answer 1

There was an answer from Matz :)

UPDATE

Also, you can use gem entitled highline, because using above example may be linked with strange screen effects:

require "highline/system_extensions"
include HighLine::SystemExtensions

while k = get_character
  print k.chr
end

Answer 2

Adapted from from another answered question.

def get_char
  begin
    system("stty raw -echo")
    str = STDIN.getc
  ensure
    system("stty -raw echo")
  end
  str.chr
end

p get_char # => "q"

Answer 3

https://stackoverflow.com/a/27021816/203673 and its comments are the best answer in the ruby 2+ world. This will block to read a single character and exit when ctrl + c is pressed:

require 'io/console'

STDIN.getch.tap { |char| exit(1) if char == "\u0003" }

Answer 4

From https://flylib.com/books/en/2.44.1/getting_input_one_character_at_a_time.html

def getch
  state = `stty -g`
  begin
    `stty raw -echo cbreak`
    $stdin.getc
  ensure
    `stty #{state}`
  end
end

while (k = getch)
  print k.chr.inspect
  sleep 0.2
end