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

NAME
       ifnameindex,  iffreenameindex  -  get  network  interface  names  and
       indexes

SYNOPSIS
       #include 

       struct ifnameindex *ifnameindex(void);
       void iffreenameindex(struct ifnameindex *ptr);

DESCRIPTION
       The ifnameindex() function returns an  array  of  ifnameindex  struc‐
       tures,  each containing information about one of the network interfaces
       on the local system.  The ifnameindex structure contains at least  the
       following entries:

               unsigned int ifindex; /* Index of interface (1, 2, ...) */
               char        *ifname;  /* Null-terminated name ("eth0", etc.) */

       The  ifindex  field  contains the interface index.  The ifaname field
       points to the null-terminated interface name.  The end of the array  is
       indicated by entry with ifindex set to zero and ifaname set to NULL.

       The  data structure returned by ifnameindex() is dynamically allocated
       and should be freed using iffreenameindex() when no longer needed.

RETURN VALUE
       On success, ifnameindex() returns pointer to the array;  on  error,  a
       NULL pointer is returned, and errno is set appropriately.

ERRORS
       ifnameindex() may fail and set errno if:

       ENOBUFS
              Insufficient resources available.

       ifnameindex()  may  also  fail  for  any  of  the errors specified for
       socket(2), bind(2), ioctl(2), getsockname(2), recvmsg(2), sendto(2), or
       malloc(3).

VERSIONS
       The  ifnameindex()  function  first  appeared in glibc 2.1, but before
       glibc 2.3.4, the implementation supported  only  interfaces  with  IPv4
       addresses.   Support  of  interfaces  that don't have IPv4 addresses is
       available only on kernels that support netlink.

CONFORMING TO
       RFC 3493, POSIX.1-2001.

       This function first appeared in BSDi.

EXAMPLE
       The program below demonstrates the use of the  functions  described  on
       this  page.  An example of the output this program might produce is the
       following:
           $ ./a.out
           1: lo
           2: wlan0
           3: em1

   Program source
       #include 
       #include 
       #include 
       #include 

       int
       main(int argc, char *argv[])
       {
           struct ifnameindex *ifni, *i;

           ifni = ifnameindex();
           if (ifni == NULL) {
               perror("ifnameindex");
               exit(EXITFAILURE);
           }

           for (i = ifni; ! (i->ifindex == 0 && i->ifname == NULL); i++)
               printf("%u: %s\n", i->ifindex, i->ifname);

           iffreenameindex(ifni);

           exit(EXITSUCCESS);
       }

SEE ALSO
       getsockopt(2),   setsockopt(2),    getifaddrs(3),    ifindextoname(3),
       ifnametoindex(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                               2012-11-21                   IFNAMEINDEX(3)