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if_nameindex, if_freenameindex — get network interface names and indexes
#include <net/if.h>
struct if_nameindex
*if_nameindex( |
void); |
void
if_freenameindex( |
struct if_nameindex *ptr); |
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.
On success, if_nameindex()
returns pointer to the array; on error, a NULL pointer is
returned, and errno is set
appropriately.
if_nameindex() may fail and
set errno if:
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).
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.
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.out1: lo 2: wlan0 3: em1
#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);
}
getsockopt(2), setsockopt(2), getifaddrs(3), if_indextoname(3), if_nametoindex(3), ifconfig(8)
This page is part of release 3.52 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/.
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Copyright (c) 2012 YOSHIFUJI Hideaki <yoshfujilinux-ipv6.org> and Copyright (c) 2012 Michael Kerrisk <mtk.manpagesgmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END |