NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | EXAMPLE | SEE ALSO | COLOPHON

IF_NAMEINDEX(3)           Linux Programmer's Manual          IF_NAMEINDEX(3)

NAME         top

       if_nameindex,  if_freenameindex  -  get  network  interface names and
       indexes

SYNOPSIS         top

       #include <net/if.h>

       struct if_nameindex *if_nameindex(void);
       void if_freenameindex(struct if_nameindex *ptr);

DESCRIPTION         top

       The if_nameindex() function returns an array of if_nameindex
       structures, each containing information about one of the network
       interfaces on the local system.  The if_nameindex structure contains
       at least the following entries:

               unsigned int if_index; /* Index of interface (1, 2, ...) */
               char        *if_name;  /* Null-terminated name ("eth0", etc.) */

       The if_index field contains the interface index.  The ifa_name field
       points to the null-terminated interface name.  The end of the array
       is indicated by entry with if_index set to zero and ifa_name set to
       NULL.

       The data structure returned by if_nameindex() is dynamically
       allocated and should be freed using if_freenameindex() when no longer
       needed.

RETURN VALUE         top

       On success, if_nameindex() returns pointer to the array; on error,
       NULL is returned, and errno is set appropriately.

ERRORS         top

       if_nameindex() may fail and set errno if:

       ENOBUFS
              Insufficient resources available.

       if_nameindex() may also fail for any of the errors specified for
       socket(2), bind(2), ioctl(2), getsockname(2), recvmsg(2), sendto(2),
       or malloc(3).

VERSIONS         top

       The if_nameindex() function first appeared in glibc 2.1, but before
       glibc 2.3.4, the implementation supported only interfaces with IPv4
       addresses.  Support of interfaces that don't have IPv4 addresses is
       available only on kernels that support netlink.

CONFORMING TO         top

       RFC 3493, POSIX.1-2001.

       This function first appeared in BSDi.

EXAMPLE         top

       The program below demonstrates the use of the functions described on
       this page.  An example of the output this program might produce is
       the following:

           $ ./a.out
           1: lo
           2: wlan0
           3: em1

   Program source
       #include <net/if.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <unistd.h>

       int
       main(int argc, char *argv[])
       {
           struct if_nameindex *if_ni, *i;

           if_ni = if_nameindex();
           if (if_ni == NULL) {
               perror("if_nameindex");
               exit(EXIT_FAILURE);
           }

           for (i = if_ni; ! (i->if_index == 0 && i->if_name == NULL); i++)
               printf("%u: %s\n", i->if_index, i->if_name);

           if_freenameindex(if_ni);

           exit(EXIT_SUCCESS);
       }

SEE ALSO         top

       getsockopt(2), setsockopt(2), getifaddrs(3), if_indextoname(3),
       if_nametoindex(3), ifconfig(8)

COLOPHON         top

       This page is part of release 3.65 of the Linux man-pages project.  A
       description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

GNU                              2012-11-21                  IF_NAMEINDEX(3)