Sample C Program To Display Function Without Using The Main Function.

# include <stdio.h>
#define decode(s,t,u,m,p,e,d) m##s##u##t
#define begin decode(a,n,i,m,a,t,e)

int begin()
{
    printf(" helloworld ");
}

OUTPUT:

helloworld




Sample C Program To Get IP Address.

# include <stdio.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 <unistd.h>
#include

int main()
{

    int n;
    struct ifreq ifr;
    char array[] = "eth0";
    n = socket(AF_INET, SOCK_DGRAM, 0);

    //Type of address to retrieve - IPv4 IP address

    ifr.ifr_addr.sa_family = AF_INET;

    //Copy the interface name in the ifreq structure

    strncpy(ifr.ifr_name , array , IFNAMSIZ - 1);

    ioctl(n, SIOCGIFADDR, &ifr);
    close(n);

    //display result
    printf("IP Address is %s - %s\n" , array , inet_ntoa(( (struct sockaddr_in *)&ifr.ifr_addr )->sin_addr) );

    return 0;
}


OUTPUT:

IP Address is eth0 - 192.8.5.1