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.\"     $OpenBSD: ethers.3,v 1.14 2001/08/06 10:42:26 mpech Exp $

.\"

.\" Written by roland@frob.com.  Public domain.

.\"

.Dd December 16, 1993

.Dt ETHERS 3

.Os

.Sh NAME

.Nm ether_aton ,

.Nm ether_ntoa ,

.Nm ether_addr ,

.Nm ether_ntohost ,

.Nm ether_hostton ,

.Nm ether_line

.Nd get ethers entry

.Sh SYNOPSIS

.Fd #include 

.Ft char *

.Fn ether_ntoa "struct ether_addr *e"

.Ft struct ether_addr *

.Fn ether_aton "char *s"

.Ft int

.Fn ether_ntohost "char *hostname" "struct ether_addr *e"

.Ft int

.Fn ether_hostton "char *hostname" "struct ether_addr *e"

.Ft int

.Fn ether_line "char *l" "struct ether_addr *e" "char *hostname"

.Sh DESCRIPTION

Ethernet addresses are represented by the

following structure:

.Bd -literal -offset indent

struct ether_addr {

        u_int8_t  ether_addr_octet[6];

};

.Ed

.Pp

The

.Fn ether_ntoa

function converts this structure into an

.Tn ASCII

string of the form

.Dq xx:xx:xx:xx:xx:xx ,

consisting of 6 hexadecimal numbers separated

by colons.

It returns a pointer to a static buffer that is reused for each call.

The

.Fn ether_aton

converts an

.Tn ASCII

string of the same form and to a structure

containing the 6 octets of the address.

It returns a pointer to a static structure that is reused for each call.

.Pp

The

.Fn ether_ntohost

and

.Fn ether_hostton

functions interrogate the database mapping host names to Ethernet

addresses,

.Pa /etc/ethers .

The

.Fn ether_ntohost

function looks up the given Ethernet address and writes the associated

host name into the character buffer passed.

This buffer should be

.Dv MAXHOSTNAMELEN

characters in size.

The

.Fn ether_hostton

function looks up the given host name and writes the associated

Ethernet address into the structure passed.

Both functions return

zero if they find the requested host name or address, and \-1 if not.

.Pp

Each call reads

.Pa /etc/ethers

from the beginning; if a

.Ql +

appears alone on a line in the file, then

.Fn ether_hostton

will consult the

.Pa ethers.byname

YP map, and

.Fn ether_ntohost

will consult the

.Pa ethers.byaddr

YP map.

.Pp

The

.Fn ether_line

function parses a line from the

.Pa /etc/ethers

file and fills in the passed

.Li struct ether_addr

and character buffer with the Ethernet address and host name on the line.

It returns zero if the line was successfully parsed and \-1 if not.

The character buffer should be

.Dv MAXHOSTNAMELEN

characters in size.

.Sh FILES

.Bl -tag -width /etc/ethers -compact

.It Pa /etc/ethers

.El

.Sh SEE ALSO

.Xr ethers 5

.Sh HISTORY

The

.Fn ether_ntoa ,

.Fn ether_aton ,

.Fn ether_ntohost ,

.Fn ether_hostton ,

and

.Fn ether_line

functions were adopted from SunOS and appeared in

.Nx 0.9 b.

.Sh BUGS

The data space used by these functions is static; if future use

requires the data, it should be copied before any subsequent calls to

these functions overwrite it.