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.\" $OpenBSD: getnetent.3,v 1.17 2017/11/28 18:10:59 schwarze Exp $
.\"
.\" Copyright (c) 1983, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" notice, this list of conditions and the following disclaimer.
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.\" notice, this list of conditions and the following disclaimer in the
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.\" 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
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" SUCH DAMAGE.
.\"
.Dd $Mdocdate: November 28 2017 $
.Dt GETNETENT 3
.Os
.Sh NAME
.Nm getnetent ,
.Nm getnetbyaddr ,
.Nm getnetbyname ,
.Nm setnetent ,
.Nm endnetent
.Nd get network entry
.Sh SYNOPSIS
.In netdb.h
.Ft struct netent *
.Fn getnetent "void"
.Ft struct netent *
.Fn getnetbyname "const char *name"
.Ft struct netent *
.Fn getnetbyaddr "in_addr_t net" "int type"
.Ft void
.Fn setnetent "int stayopen"
.Ft void
.Fn endnetent "void"
.Sh DESCRIPTION
The
.Fn getnetent ,
.Fn getnetbyname ,
and
.Fn getnetbyaddr
functions each return a pointer to an object with the following structure
containing the broken-out fields of a line in the network database,
.Pa /etc/networks .
.Bd -literal -offset indent
struct netent {
char *n_name; /* official name of net */
char **n_aliases; /* alias list */
int n_addrtype; /* net number type */
in_addr_t n_net; /* net number */
};
.Ed
.Pp
The members of this structure are:
.Bl -tag -width n_addrtype
.It Fa n_name
The official name of the network.
.It Fa n_aliases
A null-terminated list of alternate names for the network.
.It Fa n_addrtype
The type of the network number returned; currently only
.Dv AF_INET .
.It Fa n_net
The network number.
Network numbers are returned in machine byte order.
.El
.Pp
The
.Fn getnetent
function reads the next line of the file, opening the file if necessary.
.Pp
The
.Fn setnetent
function opens and rewinds the file.
If the
.Fa stayopen
flag is non-zero,
the net database will not be closed after each call to
.Fn getnetbyname
or
.Fn getnetbyaddr .
.Pp
The
.Fn endnetent
function closes the file.
.Pp
The
.Fn getnetbyname
and
.Fn getnetbyaddr
functions search the domain name server if the system is configured to use one.
If the search fails, or no name server is configured, they sequentially
search from the beginning of the file until a matching net name or
net address and type is found, or until
.Dv EOF
is encountered.
Network numbers are supplied in host order.
.Sh RETURN VALUES
The
.Fn getnetent ,
.Fn getnetbyaddr ,
and
.Fn getnetbyname
functions return
.Dv NULL
if the requested entry is not found.
.Sh FILES
.Bl -tag -width /etc/networks -compact
.It Pa /etc/networks
.El
.Sh SEE ALSO
.Xr resolver 3 ,
.Xr networks 5
.Sh STANDARDS
These functions conform to
.St -p1003.1-2008 .
.Sh HISTORY
The
.Fn getnetent ,
.Fn getnetbyaddr ,
.Fn getnetbyname ,
.Fn setnetent ,
and
.Fn endnetent
functions appeared in
.Bx 4.2 .
.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.
Only Internet network numbers are currently understood.
Expecting network numbers to fit in no more than 32 bits is naive.
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