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IF_NAMETOINDEX(3)	     Library Functions Manual	       IF_NAMETOINDEX(3)

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

SYNOPSIS
     #include <sys/types.h>
     #include <sys/socket.h>
     #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 corresponding 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 allocated
     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 occurs
     while retrieving the list of interfaces via getifaddrs(3).

     Upon successful completion, if_indextoname() returns ifname.  If the inter-
     face 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 retrieving the  list
     of interfaces via getifaddrs(3).

     The if_nameindex() returns a NULL pointer if an error occurs while retriev-
     ing  the list of interfaces via getifaddrs(3), or if sufficient memory can-
     not be allocated.

SEE ALSO
     getifaddrs(3), networking(4)

STANDARDS
     The if_nametoindex(), if_indextoname(), if_nameindex(), and  if_freenamein-
     dex() functions conform to RFC 2553.

HISTORY
     The implementation first appeared in BSDi BSD/OS.

FreeBSD 14.3			November 23, 2005	       IF_NAMETOINDEX(3)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=if_freenameindex&manpath=FreeBSD+14.3-RELEASE+and+Ports>

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