Ruby - Character-wise IO.select

Question

Is there a way to have IO.select return a single input character without receiving an EOF? I would like to be able to read user input from the keyboard the same way I read from any other stream, like an open TCP socket connection. It would allow me to make an event loop like this:

loop {
  rd, _, _ = IO.select([long_lived_tcp_connection, stdin])

  case rd[0]
  when long_lived_tcp_connection
    handle_server_sent_event(rd[0].read)
  when stdin
    handle_keypress(rd[0].read)
  end
}

I've been looking into io/console but it doesn't quite give me this capability (although IO#getch comes pretty close).

*"although `IO#getch` comes pretty close`"* - what's missing? — Stefan, Nov 07 '14 at 08:52

score 2 · Accepted Answer · edited May 23 '17 at 12:25

2

You can set stdin to raw mode (taken from this answer):

begin
  state = `stty -g`
  `stty raw -echo -icanon isig`
  loop do
    rd, _, _ = IO.select([$stdin])
    handle_keypress(rd[0].getc)
  end
ensure
  `stty #{state}`
end

IO#getc returns a single character from stdin. Another option is IO#read_nonblock to read all available data.

edited May 23 '17 at 12:25

Community

1
1

answered Nov 07 '14 at 16:55

Stefan

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Awesome! This mostly works, except the `IO#getc` seems to block even if there is data to be read. Using `IO#getch` works as expected though :) – rickyrickyrice Nov 08 '14 at 06:38
Interesting, `getc` doesn't block on my system (Ruby 2.1, OS X) – Stefan Nov 08 '14 at 07:46

score 0 · Answer 2 · answered Nov 07 '14 at 07:28

0

To read one character at a time I would use:

STDIN.each_char {|char| p char}

answered Nov 07 '14 at 07:28

Aurélien Bottazini

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Ruby - Character-wise IO.select

2 Answers2