多个fork（）的并发 [英] Multiple fork() Concurrency

问题描述

如何在这样你可以生成10个进程，并让他们做一个小任务并行的方式使用fork（）的命令。

How do you use the fork() command in such a way that you can spawn 10 processes and have them do a small task concurrently.

并发是最关键的词，很多地方显示如何使用fork只使用（）在他们的演示一个调用叉。我以为你会用某种形式的for循环，但我想，它似乎在我的测试，该叉（）'s的产卵一个新的进程，做的工作，然后生成一个新的进程。因此，他们似乎正在运行顺序，但我怎么能同时叉，并有10个进程同时做的工作如果是有道理的？

Concurrent is the operative word, many places that show how to use fork only use one call to fork() in their demos. I thought you would use some kind of for loop but i tried and it seems in my tests that the fork()'s are spawning a new process, doing work, then spawning a new process. So they appear to be running sequentially but how can I fork concurrently and have 10 processes do the work simultaneously if that makes sense?

感谢。

更新：的答案家伙谢谢，我想我只是误会叉的某些方面（）开始，但我现在明白了吧。干杯。

Update: Thanks for the answers guys, I think I just misunderstood some aspects of fork() initially but i understand it now. Cheers.

推荐答案

呼叫叉（）在一个循环：

添加code等待每个孩子的意见：

Adding code to wait for children per comments:

int numberOfChildren = 10;
pid_t *childPids = NULL;
pid_t p;

/* Allocate array of child PIDs: error handling omitted for brevity */
childPids = malloc(numberOfChildren * sizeof(pid_t));

/* Start up children */
for (int ii = 0; ii < numberOfChildren; ++ii) {
   if ((p = fork()) == 0) {
      // Child process: do your work here
      exit(0);
   }
   else {
      childPids[ii] = p;
   }
}

/* Wait for children to exit */
int stillWaiting;
do {
   stillWaiting = 0;
    for (int ii = 0; ii < numberOfChildren; ++ii) {
       if (childPids[ii] > 0) {
          if (waitpid(childPids[ii], NULL, WNOHANG) != 0) {
             /* Child is done */
             childPids[ii] = 0;
          }
          else {
             /* Still waiting on this child */
             stillWaiting = 1;
          }
       }
       /* Give up timeslice and prevent hard loop: this may not work on all flavors of Unix */
       sleep(0);
    }
} while (stillWaiting);

/* Cleanup */
free(childPids);

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