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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | ATTRIBUTES | CONFORMING TO | EXAMPLES | 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
allocated 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 to indicate the error.
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(), if_freenameindex() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
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 5.13 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 2021-03-22 IF_NAMEINDEX(3)
Pages that refer to this page: if_nametoindex(3)
Copyright and license for this manual page
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