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IF_NAMETOINDEX(3)	 BSD Library Functions Manual	     IF_NAMETOINDEX(3)

NAME
     if_nametoindex, if_indextoname, if_nameindex, if_freenameindex -- provide
     mappings between interface	names and indexes

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.  If	the interface is not found, a value of 0 is returned
     and errno is set to ENXIO.	 A value of 0 is also returned if an error oc-
     curs while	retrieving the list of interfaces via getifaddrs(3).

     Upon successful completion, if_indextoname() returns ifname.  If the in-
     terface is	not found, a NULL pointer is returned and errno	is set to
     ENXIO.  A NULL pointer is also returned if	an error occurs	while retriev-
     ing 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 ALSO
     getifaddrs(3), networking(4)

STANDARDS
     The if_nametoindex(), if_indextoname(), if_nameindex(), and
     if_freenameindex()	functions conform to RFC 2553.

HISTORY
     The implementation	first appeared in BSDi BSD/OS.

BSD				 July 15, 2002				   BSD
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | SEE ALSO | STANDARDS | HISTORY

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