#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char ** argv)
{
    struct sockaddr_in in;
    struct sockaddr out;
    socklen_t inlen, outlen;
    const char * address;
    int fd, rc;

    if (argc != 2)
    {
        fprintf(stderr, "Usage: %s address\n", argv[0]);
        return 1;
    }

    address = argv[1];

    fd = socket(PF_INET, SOCK_STREAM, 0);
    if (fd == -1)
    {
        err(errno, "socket");
    }

    inlen = sizeof(in);
    memset(&in, 0, inlen);
    in.sin_family = AF_INET;
    in.sin_port = 0;
    rc = inet_pton(AF_INET, address, &in.sin_addr);
    if (rc == -1)
    {
        err(errno, "inet_pton");
    }
    else if (rc == 0)
    {
        fprintf(stderr, "inet_pton: cannot parse %s\n", argv[1]);
        return 1;
    }

    if (bind(fd, (const struct sockaddr *)&in, inlen))
    {
        err(errno, "bind");
    }

    outlen = sizeof(out);
    if (getsockname(fd, &out, &outlen))
    {
        err(errno, "getsockname");
    }

    printf("addr: %s\n", inet_ntoa(((const struct sockaddr_in *)&out)->sin_addr));
}