.\" $KAME: if_indextoname.3,v 1.10 2000/11/24 08:13:51 itojun Exp $ .\" BSDI Id: if_indextoname.3,v 2.2 2000/04/17 22:38:05 dab Exp .\" .\" Copyright (c) 1997, 2000 .\" Berkeley Software Design, Inc. 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. .\" .\" THIS SOFTWARE IS PROVIDED BY Berkeley Software Design, Inc. ``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 Berkeley Software Design, Inc. 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. .\" .\" $FreeBSD: src/lib/libc/net/if_indextoname.3,v 1.2.2.6 2002/07/29 18:33:18 ume Exp $ .\" $DragonFly: src/lib/libc/net/if_indextoname.3,v 1.2 2003/06/17 04:26:44 dillon Exp $ .\" .Dd "July 11, 1997" .Dt IF_NAMETOINDEX 3 .Os .Sh NAME .Nm if_nametoindex , .Nm if_indextoname , .Nm if_nameindex , .Nm if_freenameindex .Nd provide mappings between interface names and indexes .Sh SYNOPSIS .In net/if.h .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 .Fn if_nametoindex function maps the interface name specified in .Ar ifname to its corresponding index. If the specified interface does not exist, it returns 0. .Pp The .Fn if_indextoname function maps the interface index specified in .Ar ifindex to it corresponding name, which is copied into the buffer pointed to by .Ar ifname , which must be of at least IFNAMSIZ bytes. This pointer is also the return value of the function. If there is no interface corresponding to the specified index, NULL is returned. .Pp The .Fn if_nameindex function returns an array of .Nm if_nameindex structures, one structure per interface, as defined in the include file .Aq Pa net/if.h . The .Nm if_nameindex structure contains at least the following entries: .Bd -literal 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 .Nm if_index of 0 and an .Nm if_name of NULL. A NULL pointer is returned upon an error. .Pp The .Fn if_freenameindex function frees the dynamic memory that was allocated by .Fn if_nameindex . .Sh RETURN VALUES Upon successful completion, .Fn if_nametoindex returns the index number of the interface. If the interface is not found, a value of 0 is returned and .Va errno is set to .Er ENXIO . A value of 0 is also returned if an error occurs while retrieving the list of interfaces via .Xr getifaddrs 3 . .Pp Upon successful completion, .Fn if_indextoname returns .Ar ifname . If the interface is not found, a NULL pointer is returned and .Va errno is set to .Er ENXIO . A NULL pointer is also returned if an error occurs while retrieving the list of interfaces via .Xr getifaddrs 3 . .Pp The .Fn if_nameindex returns a NULL pointer if an error occurs while retrieving the list of interfaces via .Xr getifaddrs 3 , or if sufficient memory cannot be allocated. .Sh SEE ALSO .Xr getifaddrs 3 , .Xr networking 4 .Sh STANDARDS The .Fn if_nametoindex , .Fn if_indextoname , .Fn if_nameindex , and .Fn if_freenameindex functions conform to RFC 2553. .Sh HISTORY The implementation first appeared in BSDI BSD/OS.