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.
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
#include <net/if.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int
main(void)
{
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)