C并发进程和管道-CConcurrentProcessesandaPipe

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printing after the for() loop the value returned from getpid() will be printed both for the (many) child pids and the parent pid.

在for（）循环之后打印从getpid（）返回的值将被打印为（多个）子pid和父pid。

There is no guarantee as to what process will execute to the call to printf() first.

无法保证首先对printf（）的调用执行什么进程。

so the pid values can (and as you have seen) probably will) be printed in some 'random' order.

所以pid值可以（并且如你所见）可能会以某种“随机”顺序打印。

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When you fork a child process, the parent and child both run concurrently. Unless they do something that synchronizes them, the order that they each run is unpredictable.

分叉子进程时，父进程和子进程同时运行。除非他们做同步它们的事情，否则它们每次运行的顺序是不可预测的。

In the case of your for loop, the reads and writes in the pipes are synchronizing the processes: the parent can't return from read() until after the child has called write(). And they won't fork new children until both have done this.

在for循环的情况下，管道中的读取和写入正在同步进程：在子进程调用write（）之后，父进程无法从read（）返回。并且他们不会分娩新孩子，直到他们都这样做。

But after the loop is done, there's nothing synchronizing the processes, so they'll all print their PIDs in any order.

但是在循环完成之后，没有任何东西可以同步进程，所以它们都会以任何顺序打印它们的PID。