linux man page for if_indextoname

IF_NAMETOINDEX(3)					     Linux Programmer's Manual						 IF_NAMETOINDEX(3)

NAME
       if_nametoindex, if_indextoname - mappings between network interface names and indexes

SYNOPSIS
       #include <net/if.h>

       unsigned int if_nametoindex(const char *ifname);

       char *if_indextoname(unsigned int ifindex, char *ifname);

DESCRIPTION
       The if_nametoindex() function returns the index of the network interface corresponding to the name ifname.

       The  if_indextoname()  function returns the name of the network interface corresponding to the interface index ifindex.	The name is placed
       in the buffer pointed to by ifname.  The buffer must allow for the storage of at least IF_NAMESIZE bytes.

RETURN VALUE
       On success, if_nametoindex() returns the index number of the network interface; on error, 0 is returned and errno is set appropriately.

       On success, if_indextoname() returns ifname; on error, NULL is returned and errno is set appropriately.

ERRORS
       if_indextoname() may fail and set errno if:

       ENXIO  No interface found for the index.

       if_nametoindex() and if_indextoname() may also fail for any of the errors specified for socket(2) or ioctl(2).

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

       +-----------------------------------+---------------+---------+
       |Interface			   | Attribute	   | Value   |
       +-----------------------------------+---------------+---------+
       |if_nametoindex(), if_indextoname() | Thread safety | MT-Safe |
       +-----------------------------------+---------------+---------+
CONFORMING TO
       RFC 3493, POSIX.1-2001.

       This function first appeared in BSDi.

SEE ALSO
       getifaddrs(3), if_nameindex(3), ifconfig(8)

GNU
								    2015-03-02							 IF_NAMETOINDEX(3)