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

       POSIX.1-2001, POSIX.1-2008, RFC 3493.

       This function first appeared in BSDi.

SEE ALSO

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

COLOPHON

       This  page  is  part of release 4.04 of the Linux man-pages project.  A description of the
       project, information about reporting bugs, and the latest version of  this  page,  can  be
       found at http://www.kernel.org/doc/man-pages/.