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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 <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 correspond-
     ing index.  If the specified interface does not exist, it returns 0.

     The if_indextoname() function maps the interface index specified in ifindex to it corre-
     sponding 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 interface 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 retrieving the list of
     interfaces via getifaddrs(3), or if sufficient memory 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					November 23, 2005				      BSD
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