为什么某些 cmd 启动的进程在输出重定向时会阻止/缓冲输出？
为什么在我的 Windows 机器上的命令行启动的某些进程在重定向时会阻止/缓冲其整个输出，而其他进程则不会？
示例：tracert 在写入时不会阻止/缓冲输出。如果执行：
tracert ponyoverflow.com > output.txt
...output.txt 文件会随着时间的推移而增长。这完全是我所期望的事情的表现。
但是，我正在尝试使用潜在供应商的软件产品（iSpring SDK，如果您必须知道）并且它似乎会缓冲完整的输出，直到该过程完成。我感到困惑的是，当这个软件在命令行运行时，输出是零散的、逐行的，正如预期的那样。
为什么使用和不使用输出重定向调用它之间的行为存在差异？
跟进其他问题：
- 这是 Windows 命令行编程领域的常见和/或标准吗？
- 我能做些什么来获取
- 如何准确地与 iSpring 人员沟通（用 Windows 程序员的话说），我认为他们的软件应该如何在命令行上运行？
我不确定它有多重要，但我的所有这些实验都是在 64 位 Windows 7 Home Premium 计算机上进行的。
Why do some processes started at the command line on my Windows machine block/buffer their entire output if it is redirected and others not?
Example: tracert does not block/buffer output as it is written. If one executes:
tracert ponyoverflow.com > output.txt
...the output.txt file grows over time. This is completely how I would expect things to behave.
But, I'm trying to work with a potential vendor's software product (iSpring SDK, if you must know) and it seems to buffer the complete output until the process has finished. What I find confusing is that when this software is run at the command line the output comes piecemeal, line-by-line, as expected.
Why is there a difference in behavior between calling it with and without output redirection?
Follow up miscellaneous questions:
- Is this common and/or standard in the world of Windows command line programming?
- Is there anything I can do to grab the
- How do I communicate exactly, in Windows programmer parlance, to iSpring folks how I think their software should behave at the command line?
I'm not sure how important it is, but all this experimentation of mine is happening on a 64-bit Windows 7 Home Premium machine.
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（iSpring 的工作人员对我的请求的响应速度比我想象的要快得多。点对点。下面是他们对“原因”的回答。）
默认情况下，C++ 中的标准输出是缓冲的。缓冲区大小约为4KB。当应用程序完成时，缓冲区将被刷新。当标准输出与控制台连接时，写入 stdout 的数据不会被缓冲。
(The folks at iSpring were much quicker responding to me requests than I could have dreamed. Spot on. Here is their answer to 'why' below.)
Standard output in C++ is buffered by default. The buffer size is about 4KB. The buffer is flushed when the application finishes. Data written to stdout are not buffered when standard output is connected with a console.