Created
March 31, 2024 15:02
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Get Ip address with syscalls
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/* | |
** showip.c -- show IP addresses for a host given on the command line | |
** showip google.com | |
** Credit: Beej's Guide to Network Programming | |
*/ | |
#include <stdio.h> | |
#include <string.h> | |
#include <sys/types.h> | |
#include <sys/socket.h> | |
#include <netdb.h> | |
#include <arpa/inet.h> | |
#include <netinet/in.h> | |
int main(int argc, char *argv[]) | |
{ | |
struct addrinfo hints, *res, *p; | |
int status; | |
char ipstr[INET6_ADDRSTRLEN]; | |
if (argc != 2) { | |
fprintf(stderr,"usage: showip hostname\n"); | |
return 1; | |
} | |
memset(&hints, 0, sizeof hints); | |
hints.ai_family = AF_UNSPEC; // AF_INET or AF_INET6 to force version | |
hints.ai_socktype = SOCK_STREAM; | |
if ((status = getaddrinfo(argv[1], NULL, &hints, &res)) != 0) { | |
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(status)); | |
return 2; | |
} | |
printf("IP addresses for %s:\n\n", argv[1]); | |
for(p = res;p != NULL; p = p->ai_next) { | |
void *addr; | |
char *ipver; | |
// get the pointer to the address itself, | |
// different fields in IPv4 and IPv6: | |
if (p->ai_family == AF_INET) { // IPv4 | |
struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr; | |
addr = &(ipv4->sin_addr); | |
ipver = "IPv4"; | |
} else { // IPv6 | |
struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr; | |
addr = &(ipv6->sin6_addr); | |
ipver = "IPv6"; | |
} | |
// convert the IP to a string and print it: | |
inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr); | |
printf(" %s: %s\n", ipver, ipstr); | |
} | |
freeaddrinfo(res); // free the linked list | |
return 0; | |
} |
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