hot to get IP from shell -> C solution

["electa" <electabuzz at katamail dot com>]

/* little utility to get the IP address of the machine

- prints the IP address in triple-dotted form xxx.yyy.zzz.www,

or nothing if can't get it.

- this code is a fragment from EpidEm code.

*/

#include <stdio.h>

#include <arpa/inet.h>

#include <netinet/in.h>

#include <unistd.h>

#include <netdb.h>

/*

Returns the IP address of this host.

- if host have more than 1 IP, only 1 (the first) is returned.

- return is in network byte order

- thanks to Doct. Ghini (www.cs.unibo.it/~ghini)

return: 0 if unsuccessful, the IP otherwise

*/

in_addr_t get_my_IP()

{

/* have you ever seen a hostname longer than a screen (80cols)?*/

char name[80]; /*store my hostname*/

struct hostent * hostent_ptr;

int ret;

ret = gethostname (name, 80);

if(ret == -1) {

/*printf ("ERROR gethostname() failed, Errno=%d \nDescription: %s\n", errno,

strerror(errno));*/

return 0;

}


hostent_ptr = gethostbyname(name);


if(hostent_ptr == NULL)

{

/*printf ("ERROR gethostbyname() failed, h_errno=%d \nDescription: %s\n",
h_errno, hstrerror(h_errno));*/

return 0;

}

/*h_addr_list contains IPs of this host in network byte order */

return ((struct in_addr *)hostent_ptr->h_addr_list[0])->s_addr; /*get the
first IP.*/

}

int main()

{

in_addr_t my_ip = get_my_IP();

if (my_ip != 0)

{

struct in_addr temp;

temp.s_addr = my_ip;

printf("%s\n", inet_ntoa(temp));

}

return 0;

}




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