if_nametoindex(3)          Library Functions Manual          if_nametoindex(3)

NAME
       if_nametoindex, if_indextoname - mappings between network interface
       names and indexes

LIBRARY
       Standard C library (libc, -lc)

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 |
       +--------------------------------------------+---------------+---------+
STANDARDS
       POSIX.1-2008, RFC 3493.

HISTORY
       POSIX.1-2001.  BSDi.

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

Linux man-pages 6.7               2023-10-31                 if_nametoindex(3)