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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 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 to indicate the error.

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

ERRORS
       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).

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)

GNU                                                                            2021-03-22                                                              IF_NAMETOINDEX(3)