Maps an interface index to its corresponding name.
    Format
      #include  <if.h>
      char *if_indextoname  ( unsigned int ifindex, char *ifname );

1  –  Arguments

 ifindex
    The interface index.
 ifname
    Points to a buffer that is IFNAMSIZ bytes in length. (IFNAMSIZ is
    defined in the IF.H header file.) If an interface name is found,
    it is returned in the buffer.

2  –  Description

    This function maps an interface index to its corresponding name.

3  –  Return Values

    Interface name     If interface name is found, it is returned to
                       the buffer.
    NULL               If no interface name corresponds to the
                       specified index, the function returns NULL
                       and sets errno to ENXIO.

4  –  Errors

    ENXIO              No interface name corresponds to the specified
                       index.
    System error       A system error.