libevent 学习：官方案例 event-read-fifo

最新推荐文章于 2025-07-02 22:12:27 发布

空腹熊猫

最新推荐文章于 2025-07-02 22:12:27 发布

阅读量786

点赞数

CC 4.0 BY-SA版权

分类专栏： libevent

本文链接：https://blog.youkuaiyun.com/guangyacyb/article/details/86234831

libevent 专栏收录该内容

5 篇文章

订阅专栏

本文介绍了一个使用libevent库的示例，该示例通过命名管道（FIFO）进行进程间通信。服务端监听命名管道，客户端向其写入数据，服务端读取并打印。文章详细展示了代码实现，包括事件监听、信号处理及客户端数据发送。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

路径：libevent-2.1.8-stable/sample

文件 event-read-fifo.c

这个案例实现的是从命名管道读取内容。（考虑在Linux环境，删除跨平台相关代码）

#include <event2/event-config.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/queue.h>
#include <unistd.h>
#include <sys/time.h>
#include <signal.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>

#include <event2/event.h>

static void
fifo_read(evutil_socket_t fd, short event, void *arg)
{
	char buf[255];
	int len;
	struct event *ev = arg;

	fprintf(stderr, "fifo_read called with fd: %d, event: %d, arg: %p\n",
	    (int)fd, event, arg);
	len = read(fd, buf, sizeof(buf) - 1);

	if (len <= 0) {
		if (len == -1)
			perror("read");
		else if (len == 0)
			fprintf(stderr, "Connection closed\n");
		event_del(ev);
		event_base_loopbreak(event_get_base(ev));
		return;
	}

	buf[len] = '\0';
	fprintf(stdout, "Read: %s\n", buf);
}

/* On Unix, cleanup event.fifo if SIGINT is received. */
static void
signal_cb(evutil_socket_t fd, short event, void *arg)
{
	struct event_base *base = arg;
	event_base_loopbreak(base);
}

int
main(int argc, char **argv)
{
	struct event *evfifo;
	struct event_base* base;
	struct event *signal_int;
	struct stat st;
	const char *fifo = "event.fifo";
	int socket;

	if (lstat(fifo, &st) == 0) {
		if ((st.st_mode & S_IFMT) == S_IFREG) {
			errno = EEXIST;
			perror("lstat");
			exit(1);
		}
	}

	unlink(fifo);
	if (mkfifo(fifo, 0600) == -1) {
		perror("mkfifo");
		exit(1);
	}

	socket = open(fifo, O_RDONLY | O_NONBLOCK, 0);

	if (socket == -1) {
		perror("open");
		exit(1);
	}

	fprintf(stderr, "Write data to %s\n", fifo);
	fprintf(stderr, "Write data to %s %d\n", fifo, socket);
	/* Initalize the event library */
	base = event_base_new();

	/* Initalize one event */
	/* catch SIGINT so that event.fifo can be cleaned up */
	signal_int = evsignal_new(base, SIGINT, signal_cb, base);
	event_add(signal_int, NULL);

	evfifo = event_new(base, socket, EV_READ|EV_PERSIST, fifo_read,
                           event_self_cbarg());

	/* Add it to the active events, without a timeout */
	event_add(evfifo, NULL);

	event_base_dispatch(base);
	event_base_free(base);
	close(socket);
	unlink(fifo);
	libevent_global_shutdown();
	return (0);
}

编译：

gcc event-read-fifo.c -levent -o eventreadfifo

运行。

然后写一个客户端往同一个命名管道写数据：

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

#define BUFS PIPE_BUF

int main()
{
    int fd;
    int n, i;
    char buf[BUFS];
    time_t tp;

    printf("I am %d\n", getpid());
    if (access("event.fifo", F_OK) != 0)
    {
        if (mkfifo("event.fifo", 0666))
        {
            printf("event.fifo not existed, and create event.fifo failed!\n");
            exit(1);
        }
    }
    if ((fd = open("event.fifo", O_WRONLY)) < 0)
    {
        printf("Open failed!\n");
        exit(1);
    }

    for (i = 0; i < 10; i++)
    {
        time(&tp);
        n = sprintf(buf, "write_fifo %d sends %s", getpid(), ctime(&tp));
        printf("Send msg:%s", buf);
        if ((write(fd, buf, n + 1)) < 0)
        {
            printf("Write failed!\n");
            close(fd);
            exit(1);
        }
        sleep(1);
    }
    close(fd);
    exit(0);
}

编译：

gcc fifowrite.c -levent -o fifowrite

客户端输出，最后用ctrl + c 退出：

I am 5339
Send msg:write_fifo 5339 sends Thu Jan 10 09:38:41 2019
Send msg:write_fifo 5339 sends Thu Jan 10 09:38:42 2019
……
Send msg:write_fifo 5339 sends Thu Jan 10 09:38:47 2019
Send msg:write_fifo 5339 sends Thu Jan 10 09:38:48 2019
^C

服务端输出：

Write data to event.fifo
Write data to event.fifo 3
fifo_read called with fd: 3, event: 2, arg: 0x13b4870
Read: write_fifo 5339 sends Thu Jan 10 09:38:41 2019
……
fifo_read called with fd: 3, event: 2, arg: 0x13b4870
Read: write_fifo 5339 sends Thu Jan 10 09:38:48 2019

fifo_read called with fd: 3, event: 2, arg: 0x13b4870
Connection closed

结构体：