c - 当我尝试打开 fifo O_WRONLY 时，出现 "No such device or address"错误

Question

在我的代码中，我创建了一个名为“my_fifo”的 fifo，如果我在 O_WRONLY | 中打开它的话O_NONBLOCK 模式，open() 返回 -1 和错误编号“没有这样的设备或地址”，另一方面，如果我在 O_RDONLY | 打开 fifo | O_NONBLOCK 模式，它工作得很好。为什么会这样？我做错了什么吗？

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{

    char *fifoname = "my_fifo";
    mkfifo(fifoname, 0666);

    int fd;
    if ((fd = open(fifoname, O_WRONLY | O_NONBLOCK)) == -1)
    {
        perror("open pipe");
        exit(EXIT_FAILURE);
    }

    close(fd);

    exit(EXIT_SUCCESS);
}

Answer 1

查看 Linux fifo手册页:

A process can open a FIFO in nonblocking mode. In this case, opening for read-only will succeed even if no-one has opened on the write side yet, opening for write-only will fail with ENXIO (no such device or address) unless the other end has already been opened.

如果你想要非阻塞模式，你需要确保读者在写者之前打开fifo。