C language——read ip address in linux

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <net/if.h>
#include <arpa/inet.h>

//convert ip address string into uint
uint32_t ip2uint(const char *ip) {
    int a, b, c, d;
    uint32_t addr = 0;

    if (sscanf(ip, "%d.%d.%d.%d", &a, &b, &c, &d) != 4)
       return 0;

    addr = a << 24;
    addr |= b << 16;
    addr |= c << 8;
    addr |= d;
    return addr;
}

//read ip address
char * getipaddress(char * interface)
{
    int fd;
    struct ifreq ifr;

    fd = socket(AF_INET, SOCK_DGRAM, 0);
    ifr.ifr_addr.sa_family = AF_INET;    //I want to get an IPv4 IP address
    strncpy(ifr.ifr_name, interface, IFNAMSIZ - 1);    //I want IP address attached to "enp13s0"
    ioctl(fd, SIOCGIFADDR, &ifr);
    close(fd);
    return inet_ntoa(((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr);
}

int main()
{
    /* display result */
    printf("%s\n", getipaddress("enp13s0"));
    printf("%u\n", ip2uint(getipaddress("enp13s0")));
    return 0;
}

[root@localhost 桌面]# gcc tmp.c -o tmp
[root@localhost 桌面]# ./tmp
10.108.162.227
174891747
[root@localhost 桌面]#