linux阻塞和非阻塞写法

#include <fcntl.h>
#include <unistd.h>

int set_nonblocking(int fd) {
    int flags = fcntl(fd, F_GETFL, 0);
    if (flags == -1) return -1;
    flags |= O_NONBLOCK;
    return fcntl(fd, F_SETFL, flags);
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>

void write_to_fd(int fd, const char *data, size_t len) {
    ssize_t written = 0;
    while (written < len) {
        ssize_t result = write(fd, data + written, len - written);
        if (result == -1) {
            if (errno == EAGAIN || errno == EWOULDBLOCK) {
                // 缓冲区满，稍后重试
                continue;
            } else {
                perror("write");
                break;
            }
        }
        written += result;
    }
}

int main() {
    int fd = open("test.txt", O_WRONLY | O_CREAT, 0644);
    if (fd == -1) {
        perror("open");
        return 1;
    }

    set_nonblocking(fd);

    const char *message = "Hello, World!";
    write_to_fd(fd, message, strlen(message));

    close(fd);
    return 0;
}