IF_NAMETOINDEX(3) BSD Programmer's Manual IF_NAMETOINDEX(3)NAME
if_nametoindex, if_indextoname, if_nameindex, if_freenameindex - Provide
mappings between interface names and indexs.
SYNOPSIS
#include <net/if.h>
unsigned int
if_nametoindex(const char *ifname);
char *
if_indextoname(unsigned int ifindex, char *ifname);
struct if_nameindex *
if_nameindex(void);
void
if_freenameindex(struct if_nameindex *ptr);
DESCRIPTION
The if_nametoindex() function maps the interface name specified in ifname
to its corresponding index. If the specified interface does not exist,
it returns 0.
The if_indextoname() function maps the interface index specified in
ifindex to it corresponding name, which is copied into the buffer pointed
to by ifname, which must be of at least IFNAMSIZ bytes. This pointer is
also the return value of the function. If there is no interface corre-
sponding to the specified index, NULL is returned.
The if_nameindex() function returns an array of if_nameindex structures,
one structure per interface, as defined in the include file <net/if.h>.
The if_nameindex structure contains at least the following entries:
unsigned int if_index; /* 1, 2, ... */
char *if_name; /* null terminated name: "le0", ... */
The end of the array of structures is indicated by a structure with an
if_index of 0 and an if_name of NULL. A NULL pointer is returned upon an
error.
The if_freenameindex() function frees the dynamic memory that was allo-
cated by if_nameindex().
RETURN VALUES
Upon successful completion, if_nametoindex() returns the index number of
the interface. A value of 0 is returned if the interface is not found or
an error occurs while retrieving the list of interfaces via
getifaddrs(3).
Upon successful completion, if_indextoname() returns ifname. A NULL
pointer is returned if the interface is not found or an error occurs
while retrieving the list of interfaces via getifaddrs(3).
The if_nameindex() returns a NULL pointer if an error occurs while re-
trieving the list of interfaces via getifaddrs(3), or if sufficient mem-
ory cannot be allocated.
SEE ALSOgetifaddrs(3), networking(4)STANDARDS
The if_nametoindex(), if_indextoname(), if_nameindex(), and
if_freenameindex() functions conform to RFC 2133.
