在Ruby中没有getc/get的情况下检测按键(非阻塞) [英] Detect key press (non-blocking) w/o getc/gets in Ruby

问题描述

我有一个简单的任务，需要等待文件系统上的某些更改(它本质上是原型的编译器).因此，在检查文件更改后，我有一个简单的无限循环，有5秒钟的睡眠时间.

I have a simple task that needs to wait for something to change on the filesystem (it's essentially a compiler for prototypes). So I've a simple infinite loop with a 5 second sleep after the check for changed files.

loop do
  # if files changed
  #   process files
  #   and puts result
  sleep 5
end

我希望能够测试并查看是否已按下某个键，而不会阻塞循环，而不是Ctrl+C致敬.本质上，我只需要一种方法来判断是否有传入的按键，然后一种方法来抓住它们直到遇到Q，然后退出程序.

Instead of the Ctrl+C salute, I'd rather be able to test and see if a key has been pressed, without blocking the loop. Essentially I just need a way to tell if there are incoming key presses, then a way to grab them until a Q is met, then exit out of the program.

我想要的是:

def wait_for_Q
  key_is_pressed && get_ch == 'Q'
end

loop do
  # if files changed
  #   process files
  #   and puts result
  wait_for_Q or sleep 5
end

或者，这是Ruby不会做的(好)吗?

Or, is this something Ruby just doesn't do (well)?

推荐答案

这是使用IO#read_nonblock的一种方法:

def quit?
  begin
    # See if a 'Q' has been typed yet
    while c = STDIN.read_nonblock(1)
      puts "I found a #{c}"
      return true if c == 'Q'
    end
    # No 'Q' found
    false
  rescue Errno::EINTR
    puts "Well, your device seems a little slow..."
    false
  rescue Errno::EAGAIN
    # nothing was ready to be read
    puts "Nothing to be read..."
    false
  rescue EOFError
    # quit on the end of the input stream
    # (user hit CTRL-D)
    puts "Who hit CTRL-D, really?"
    true
  end
end

loop do
  puts "I'm a loop!"
  puts "Checking to see if I should quit..."
  break if quit?
  puts "Nope, let's take a nap"
  sleep 5
  puts "Onto the next iteration!"
end

puts "Oh, I quit."

请记住，即使它使用非阻塞IO，它仍然是缓冲 IO. 这意味着您的用户必须先按Q然后按<Enter>.如果你想做 无缓冲的IO，建议您检查ruby的curses库.

Bear in mind that even though this uses non-blocking IO, it's still buffered IO. That means that your users will have to hit Q then <Enter>. If you want to do unbuffered IO, I'd suggest checking out ruby's curses library.

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