C language——read ip address in linux

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#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 ", getipaddress("enp13s0"));
printf("%u ", 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]#

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