How to get a single character without pressing enter?

@Jay gave a great answer, but there are two problems:

1. You can mess up default tty state;
2. You ignore control characters (^C for SIGINT, etc).

A simple fix for that is to save previous tty state and use following parameters:

• -icanon - disable canonical input (ERASE and KILL processing);
• isig - enable the checking of characters against the special control characters INTR, QUIT, and SUSP.

In the end you would have a function like this:

def get_char
  state = `stty -g`
  `stty raw -echo -icanon isig`

  STDIN.getc.chr
ensure
  `stty #{state}`
end