linux之ioctl函数解析

[lingyun@localhost ioctl_1]$ ls
ipconfig.c
[lingyun@localhost ioctl_1]$ cat ipconfig.c 
/*********************************************************************************
 *      Copyright:  (C) 2013 fulinux<fulinux@sina.com> 
 *                  All rights reserved.
 *
 *       Filename:  ioctl.c
 *    Description:  This file 
 *                 
 *        Version:  1.0.0(08/01/2013~)
 *         Author:  fulinux <fulinux@sina.com>
 *      ChangeLog:  1, Release initial version on "08/01/2013 03:21:50 PM"
 *                 
 ********************************************************************************/


#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/ioctl.h>
#include <net/if.h>


static void usage()
{
    printf("usage: ipconfig interface ");
    exit(0);
}


int main(int argc, char **argv)
{
    struct sockaddr_in *addr;
    struct ifreq ifr;
    char *name,*address;
    int sockfd;
    if(argc != 2)
        usage();
    else
        name = argv[1];
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    strncpy(ifr.ifr_name, name, IFNAMSIZ - 1);
    if(ioctl(sockfd, SIOCGIFADDR,&ifr) == -1)
        perror("ioctl error"), exit(1);
    addr = (struct sockaddr_in *)&(ifr.ifr_addr);
    address = inet_ntoa(addr->sin_addr);
    printf("inet addr: %s ", address);
    if(ioctl(sockfd, SIOCGIFBRDADDR, &ifr) == -1)
        perror("ioctl error"),exit(1);
    addr = (struct sockaddr_in *)&ifr.ifr_broadaddr;
    address = inet_ntoa(addr->sin_addr);
    printf("broad addr: %s ", address);
    if(ioctl(sockfd, SIOCGIFNETMASK, &ifr) == -1)
        perror("ioctl error"), exit(1);
    addr = (struct sockaddr_in *)&ifr.ifr_addr;
    address = inet_ntoa(addr->sin_addr);
    printf("inet mask: %s ", address);
    printf(" ");
    exit(0);
}
[lingyun@localhost ioctl_1]$ gcc -o ipconfig ipconfig.c 
[lingyun@localhost ioctl_1]$ ./ipconfig eth0
inet addr: 192.168.1.3
broad addr: 192.168.1.255
inet mask: 255.255.255.0
 [lingyun@localhost ioctl_1]$