As the name suggests, a named pipe works like a pipe: you enter data in one end, and the same data comes out the other end.
如名所示，命名管道工作起来与管道一样：你在一端输入数据，另一端输出同样的数据。
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This feature is implemented using the popen system call, which allows one process to open a pipe to another process, either for output or input. In this case we open a pipe to the command.