linux字符设备读写

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

int main() {
    int fd = open("/dev/ttyS0", O_RDONLY | O_NONBLOCK);
    if (fd == -1) {
        perror("open");
        return 1;
    }

    char buffer[1024];
    while (1) {
        ssize_t n = read(fd, buffer, sizeof(buffer));
        if (n > 0) {
            printf("Read %zd bytes: %.*s\n", n, n, buffer);
        } else if (n == -1 && errno != EAGAIN) {
            perror("read");
            break;
        }
    }

    close(fd);
    return 0;
}

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

int main() {
    int fd = open("/dev/ttyS0", O_WRONLY);
    if (fd == -1) {
        perror("open");
        return 1;
    }

    const char *data = "Hello, World!";
    size_t data_len = strlen(data);

    ssize_t total_written = 0;
    while (total_written < data_len) {
        ssize_t written = write(fd, data + total_written, data_len - total_written);
        if (written == -1) {
            perror("write");
            break;
        }
        total_written += written;
    }

    close(fd);
    return 0;
}