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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | ATTRIBUTES | CONFORMING TO | EXAMPLE | SEE ALSO | COLOPHON |
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IF_NAMEINDEX(3) Linux Programmer's Manual IF_NAMEINDEX(3)
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 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 allo‐
cated and should be freed using if_freenameindex() when no longer
needed.
On success, if_nameindex() returns pointer to the array; on error,
NULL is returned, and errno is set appropriately.
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).
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.
For an explanation of the terms used in this section, see
attributes(7).
┌───────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├───────────────────┼───────────────┼─────────┤
│if_nameindex(), │ Thread safety │ MT-Safe │
│if_freenameindex() │ │ │
└───────────────────┴───────────────┴─────────┘
POSIX.1-2001, POSIX.1-2008, RFC 3493.
This function first appeared in BSDi.
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);
}
getsockopt(2), setsockopt(2), getifaddrs(3), if_indextoname(3),
if_nametoindex(3), ifconfig(8)
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)
Pages that refer to this page: if_nametoindex(3)
Copyright and license for this manual page
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