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到目前为止,我从未使用过 Thread,但我认为在这种情况下我必须依赖它。我想分别处理 cURL 命令行的标准输出和标准错误,因为我想将进度指示器(写入标准错误)中的回车换行:

require "open3"
cmd="curl -b cookie.txt #{url} -L -o -"
Open3.popen3(cmd) do |stdin, stdout, stderr, wait_thr|

  pid = wait_thr.pid 

  # I have to process stdout and stderr at the same time but
#asyncronously, because stdout gives much more data then the stderr
#stream. I instantiate a Thread object for reading the stderr, otherwise 
#"getc" would block the stdout processing loop.

  c=nil
  line=""
  stdout.each_char do |b| 
       STDOUT.print b

       if c==nil then
         c=""
         thr = Thread.new { 
         c=stderr.getc 
         if c=="\r" || c=="\n" then 
            STDERR.puts line 
            line=""
         else
          line<<c
         end
         c=nil
        }
  end

  #if stderr still holds some output then I process it:
  line=""
  stderr.each_char do |c|

         if c=="\r" || c=="\n" then 
            STDERR.puts line 
            line=""
         else
          line<<c
         end
  end

  exit_status = wait_thr.value.exitstatus 
  STDERR.puts exit_status

end #popen3

我的问题是如何避免在处理标准输出(stdout.each_char)时在每个循环周期创建一个新的线程实例?我认为这很耗时,我想实例化一次,然后使用它的方法,如停止和运行等。

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1 回答 1

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通常,您可以在主线程中处理其中一个stdoutstderr并实例化另一个线程来处理另一个。这是同时处理多个源的常见做法。

您需要注意多线程上下文中的内存共享。在您的情况下,line,stderr在没有同步的情况下在多个线程中共享和修改,这将导致不可预测的行为。

在大多数情况下,Ruby 会为您处理行尾。我不太需要处理\r\n在这里手动。

require "open3"
cmd="curl -b cookie.txt #{url} -L -o -"
Open3.popen3(cmd) do |stdin, stdout, stderr, wait_thr|
  pid = wait_thr.pid

  stdout_thread = Thread.new do
    # process stdout in another thread
    # you can replace this with the logic you want, 
    # if the following behavior isn't what you want
    stdout.each_line do |line|
      puts line
    end
  end

  # process stderr in the main thread
  stderr.each_line do |line|
    STDERR.puts line
  end

  # wait the stdout processing to be finished.
  stdout_thread.join
end
于 2015-07-06T16:38:35.310 回答