刚接触C语言，不是很懂

Question

#include <stdio.h>
#include <unistd.h>
#include <sys/socket.h>
#include <linux/if.h>
#include <linux/sockios.h>
2.定义函数
int check_link(const char *ifname)
{
    int fd;
    struct ifreq ifr;

    fd = socket(AF_INET, SOCK_DGRAM, 0);
    if (fd < 0) {
        perror("socket");
        return -1;
    }

    memset(&ifr, 0, sizeof(ifr));
    strncpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name) - 1);

    if ((ioctl(fd, SIOCGIFFLAGS, &ifr) == 0) && (ifr.ifr_flags & IFF_RUNNING)) {
        printf("%s is up.\n", ifname);
        close(fd);
        return 1;
    }
    else {
        printf("%s is down.\n", ifname);
        close(fd);
        return 0;
    }
}
3.调用函数
int main(int argc, char *argv[])
{
    if (argc < 2) {
        fprintf(stderr, "Usage: %s <interface name>\n", argv[0]);
        return 1;
    }

    if (check_link(argv[1]) < 0) {
        fprintf(stderr, "Failed to check the link.\n");
        return 1;
    }

    return 0;
}

Answer 1

socket是跟网络通信相关的类
参数SOCK_DGRAM代表UDP协议
你呀，一句一句的看，哪一句看不懂就查哪一句，都看不懂当然茫然了