我们可以使用轮询功能的命名管道？ [英] can we use poll function with unnamed pipes?

问题描述

我试图写一个程序，我需要监测无名管道两端的某些事件。我可以使用命名管道与轮询功能。

I am trying to write a program where i need to monitor ends of unnamed pipe for certain events. Can i use unnamed pipes with poll function.

如果有，可以请你告诉我与功能描述poll函数语法

If yes, can you please show me the syntax for poll function with functional descriptors

推荐答案

要使用调查检查 readfd 可读或 writefd 是可写的：

An example of poll

To use poll to check if readfd is readable or writefd is writable:

int readfd;
int writefd;

// initialize readfd & writefd, ...
// e.g. with: open(2), socket(2), pipe(2), dup(2) syscalls

struct pollfd fdtab[2];

memset (fdtab, 0, sizeof(fdtab)); // not necessary, but I am paranoid

// first slot for readfd polled for input
fdtab[0].fd = readfd;
fdtab[0].events = POLLIN;
fdtab[0].revents = 0;

// second slot with writefd polled for output
fdtab[1].fd = writefd;
fdtab[1].events = POLLOUT;
fdtab[1].revents = 0;

// do the poll(2) syscall with a 100 millisecond timeout
int retpoll = poll(fdtab, 2, 100);

if (retpoll > 0) {
   if (fdtab[0].revents & POLLIN) {
      /* read from readfd, 
         since you can read from it without being blocked */
   }
   if (fdtab[1].revents & POLLOUT) {
      /* write to writefd,
         since you can write to it without being blocked */
   }
}
else if (retpoll == 0) {
   /* the poll has timed out, nothing can be read or written */
}
else {
   /* the poll failed */
   perror("poll failed");
}

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