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
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¶
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 (), if_freenameindex () |
Thread safety |
MT-Safe |
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\n", 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 4.10 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/.