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 inter-
face 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 er-
ror.
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 er-
rors specified for socket(2) or ioctl(2).
ATTRIBUTES
For an explanation of the terms used in this section, see at-
tributes(7).
┌────────────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├────────────────────────────────────────────┼───────────────┼─────────┤
│if_nametoindex(), if_indextoname() │ Thread safety │ MT-Safe │
└────────────────────────────────────────────┴───────────────┴─────────┘
STANDARDS
POSIX.1-2001, POSIX.1-2008, RFC 3493.
This function first appeared in BSDi.
SEE ALSO
getifaddrs(3), if_nameindex(3), ifconfig(8)
Linux man-pages 6.03 2022-12-15 if_nametoindex(3)
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