在Ruby中并行操作打印输出而不会混淆输出的最简单方法是什么？

Question

说我分叉了一堆线程，并想从每个线程打印进度输出到STDERR。我怎样才能确保输出保持行原子性，即不会混淆同一输出行中不同线程的输出？

# run this a few times and you'll see the problem 
threads = []  
10.times do 
    threads << Thread.new do   
    puts "hello" * 40 
    end  
end 
threads.each {|t| t.join} 

Answer 1

由于可能会从行中单独写入新行，因此存在竞争条件。您可以在多线程应用程序中使用看跌期权看到这种噪音：

thread 0thread 1 
thread 0thread 2 
thread 1 
thread 0thread 3 
thread 2 
thread 1 

相反，使用print或printf

print "thread #{i}" + "\n" 
print "thread #{i}\n" 
printf "thread %d\n", i 

或者，因为你要写入STDERR：

$stderr.print "thread #{i}\n" 

---

这是Ruby中的错误吗？不是如果评论是作为标准。这里是从MRI 1.8.7到2.2.2的IO.puts的定义：

/* 
* call-seq: 
*  ios.puts(obj, ...) => nil 
* 
* Writes the given objects to <em>ios</em> as with 
* <code>IO#print</code>. Writes a record separator (typically a 
* newline) after any that do not already end with a newline sequence. 
* If called with an array argument, writes each element on a new line. 
* If called without arguments, outputs a single record separator. 
* 
*  $stdout.puts("this", "is", "a", "test") 
* 
* <em>produces:</em> 
* 
*  this 
*  is 
*  a 
*  test 
*/