if_nametoindex, if_indextoname - mappings between network interface names and indexes

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ if_nametoindex(), if_indextoname()                                          │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

       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.

if_nametoindex() may fail and set errno if:

       ENODEV No interface found with given name.

       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).

       POSIX.1-2001.  BSDi.

       Standard C library (libc, -lc)

       if_nametoindex, if_indextoname - mappings between network interface names and indexes

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

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

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

Linux man-pages 6.9.1                              2024-05-02                                  if_nametoindex(3)

       POSIX.1-2008, RFC 3493.

#include<net/if.h>unsignedintif_nametoindex(constchar*ifname);char*if_indextoname(unsignedintifindex,char*ifname);