LinuxQuestions.org - Getting Network Interface Information

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Getting Network Interface Information

I am using Redhat Linux 7.2 and C programming language. I want to know two things:

1. How to get the list of Network interfaces the system has?

2. How to get the IP addresses (IPv4/IPv6) associated with each interface?

any comments on this will be appreciated..

Thanx leed_25 but i want some function call which does this within my C program. I dont want to use the system call and parsing.

Well you can read the information directly from the proc filesystem. But the proc filesystem isn't always present and you will have to write a parser for the information which isn't always convenient.

There are other ways to get information using ioctls. You should read the following manpage: 'man 7 netdevice'

Well since I was curious on how it actually worked, I wrote a small program which gets a list of all the interfaces and their ip numbers. Well here is the source code:

Code:

#include <sys/ioctl.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <net/if.h>



int main()

{

  struct ifconf conf;

  struct sockaddr_in *s_in;

  int sock, i, count;



  // Open dummy socket

  if ((sock = socket(PF_INET, SOCK_DGRAM, 0)) == -1)

  {

    perror("error opening socket");

    return -1;

  }



  // Get list of devices (only gets first 10)

  memset(&conf, 0, sizeof(conf));

  conf.ifc_len = sizeof(struct ifreq) * 10;

  conf.ifc_buf = (char*) malloc(conf.ifc_len);

        

  if (ioctl(sock, SIOCGIFCONF, &conf) == -1)

  {

    perror("failed to get device list");

    return -1;

  }



  count = conf.ifc_len / sizeof(struct ifreq);



  for (i = 0; i < count; i++)

  {

    s_in = (struct sockaddr_in*) &conf.ifc_req[i].ifr_addr;

    printf("%s %s\n", conf.ifc_req[i].ifr_name,

                      inet_ntoa(s_in->sin_addr));

  }



  free(conf.ifc_buf);



  return 0;

}

Thanx for the code Nik. It was great help.