.\" Copyright (c) 1983, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" From: @(#)rcmd.3 8.1 (Berkeley) 6/4/93 .\" $FreeBSD: src/lib/libc/net/if_indextoname.3,v 1.2.2.4 2001/08/17 15:42:38 ru Exp $ .\" .Dd May 21, 1998 .Dt IF_NAMETOINDEX 3 .Os .Sh NAME .Nm if_nametoindex , .Nm if_indextoname , .Nm if_nameindex , .Nm if_freenameindex .Nd convert interface index to name, and vice versa .Sh LIBRARY .Lb libc .Sh SYNOPSIS .Fd #include .Fd #include .Fd #include .Ft "unsigned int" .Fn if_nametoindex "const char *ifname" .Ft "char *" .Fn if_indextoname "unsigned int ifindex" "char *ifname" .Ft "struct if_nameindex *" .Fn if_nameindex "void" .Ft "void" .Fn if_freenameindex "struct if_nameindex *ptr" .Sh DESCRIPTION The functions map interface index to readable interface name (such as .Dq Li lo0 ) , and vice versa. .Pp .Fn if_nametoindex converts readable interface name to interface index .Pp positive integer value . If the specified interface does not exist, 0 will be returned. .Pp .Fn if_indextoname converts interface index to readable interface name. The .Fa ifname argument must point to a buffer of at least .Dv IF_NAMESIZE bytes into which the interface name corresponding to the specified index is returned. .Dv ( IF_NAMESIZE is also defined in .Aq Pa net/if.h and its value includes a terminating null byte at the end of the interface name.) This pointer is also the return value of the function. If there is no interface corresponding to the specified index, .Dv NULL is returned. .Pp .Fn if_nameindex returns an array of .Fa if_nameindex structures. .Fa if_nametoindex is also defined in .Aq Pa net/if.h , and is as follows: .Bd -literal -offset struct if_nameindex { unsigned int if_index; /* 1, 2, ... */ char *if_name; /* null terminated name: "le0", ... */ }; .Ed .Pp The end of the array of structures is indicated by a structure with an .Fa if_index of 0 and an .Fa if_name of .Dv NULL . The function returns a .Dv NULL pointer upon an error. The memory used for this array of structures along with the interface names pointed to by the .Fa if_name members is obtained dynamically. This memory is freed by the .Fn if_freenameindex function. .Pp .Fn if_freenameindex takes a pointer that was returned by .Fn if_nameindex as argument .Pq Fa ptr , and it reclaims the region allocated. .Sh DIAGNOSTICS .Fn if_nametoindex returns 0 on error, positive integer on success. .Fn if_indextoname and .Fn if_nameindex return .Dv NULL on errors. .Sh SEE ALSO R. Gilligan, S. Thomson, J. Bound, and W. Stevens, ``Basic Socket Interface Extensions for IPv6,'' RFC2553, March 1999. .Sh HISTORY The implementation first appeared in WIDE Hydrangea IPv6 protocol stack kit. .Sh STANDARDS These functions are defined in ``Basic Socket Interface Extensions for IPv6'' (RFC2533).