plan9 man page for if_nameindex

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

NAME
       if_nameindex, if_freenameindex - get network interface names and indexes

SYNOPSIS
       #include <net/if.h>

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

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

ERRORS
       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
       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.

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

       +-------------------+---------------+---------+
       |Interface	   | Attribute	   | Value   |
       +-------------------+---------------+---------+
       |if_nameindex(),    | Thread safety | MT-Safe |
       |if_freenameindex() |		   |	     |
       +-------------------+---------------+---------+

CONFORMING TO
       POSIX.1-2001, POSIX.1-2008, RFC 3493.

       This function first appeared in BSDi.

EXAMPLE
       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
", i->if_index, i->if_name);

	   if_freenameindex(if_ni);

	   exit(EXIT_SUCCESS);
       }

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

COLOPHON
       This page is part of release 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and  the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

GNU
								    2017-09-15							   IF_NAMEINDEX(3)