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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  inter-
       face 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).
CONFORMING TO
       RFC 3493, POSIX.1-2001.
       This function first appeared in BSDi.
SEE ALSO
       getifaddrs(3), if_nameindex(3), ifconfig(8)
COLOPHON
       This  page  is  part of release 3.53 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

GNU                               2012-12-14                 IF_NAMETOINDEX(3)