xref: /dragonfly/lib/libc/net/getnetent.3 (revision 1b1d847f) 
1.\" Copyright (c) 1983, 1991, 1993
2.\"	The Regents of the University of California.  All rights reserved.
3.\"
4.\" Redistribution and use in source and binary forms, with or without
5.\" modification, are permitted provided that the following conditions
6.\" are met:
7.\" 1. Redistributions of source code must retain the above copyright
8.\"    notice, this list of conditions and the following disclaimer.
9.\" 2. Redistributions in binary form must reproduce the above copyright
10.\"    notice, this list of conditions and the following disclaimer in the
11.\"    documentation and/or other materials provided with the distribution.
12.\" 3. Neither the name of the University nor the names of its contributors
13.\"    may be used to endorse or promote products derived from this software
14.\"    without specific prior written permission.
15.\"
16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26.\" SUCH DAMAGE.
27.\"
28.\"     @(#)getnetent.3	8.1 (Berkeley) 6/4/93
29.\" $FreeBSD: src/lib/libc/net/getnetent.3,v 1.23 2007/01/09 00:28:02 imp Exp $
30.\"
31.Dd May 5, 2019
32.Dt GETNETENT 3
33.Os
34.Sh NAME
35.Nm getnetent ,
36.Nm getnetbyaddr ,
37.Nm getnetbyname ,
38.Nm setnetent ,
39.Nm endnetent
40.Nd get network entry
41.Sh LIBRARY
42.Lb libc
43.Sh SYNOPSIS
44.In netdb.h
45.Ft struct netent *
46.Fn getnetent void
47.Ft struct netent *
48.Fn getnetbyname "const char *name"
49.Ft struct netent *
50.Fn getnetbyaddr "uint32_t net" "int type"
51.Ft void
52.Fn setnetent "int stayopen"
53.Ft void
54.Fn endnetent void
55.Sh DESCRIPTION
56The
57.Fn getnetent ,
58.Fn getnetbyname ,
59and
60.Fn getnetbyaddr
61functions
62each return a pointer to an object with the
63following structure describing an internet network.
64This structure contains either the information obtained
65from the nameserver,
66.Xr named 8 ,
67broken-out fields of a line in the network data base
68.Pa /etc/networks ,
69or entries supplied by the
70.Xr yp 8
71system.
72The order of the lookups is controlled by the
73`networks' entry in
74.Xr nsswitch.conf 5 .
75.Bd -literal -offset indent
76struct	netent {
77	char		*n_name;	/* official name of net */
78	char		**n_aliases;	/* alias list */
79	int		n_addrtype;	/* net number type */
80	uint32_t	n_net;		/* net number */
81};
82.Ed
83.Pp
84The members of this structure are:
85.Bl -tag -width n_addrtype
86.It Fa n_name
87The official name of the network.
88.It Fa n_aliases
89A zero terminated list of alternate names for the network.
90.It Fa n_addrtype
91The type of the network number returned; currently only AF_INET.
92.It Fa n_net
93The network number.
94Network numbers are returned in machine byte
95order.
96.El
97.Pp
98The
99.Fn getnetent
100function
101reads the next line of the file, opening the file if necessary.
102.Pp
103The
104.Fn setnetent
105function
106opens and rewinds the file.
107If the
108.Fa stayopen
109flag is non-zero,
110the net data base will not be closed after each call to
111.Fn getnetbyname
112or
113.Fn getnetbyaddr .
114.Pp
115The
116.Fn endnetent
117function
118closes the file.
119.Pp
120The
121.Fn getnetbyname
122function
123and
124.Fn getnetbyaddr
125sequentially search from the beginning
126of the file until a matching
127net name or
128net address and type is found,
129or until
130.Dv EOF
131is encountered.
132The
133.Fa type
134argument
135must be
136.Dv AF_INET .
137Network numbers are supplied in host order.
138.Sh RETURN VALUES
139.Dv NULL
140returned on
141.Dv EOF
142or error.
143.Sh FILES
144.Bl -tag -width /etc/nsswitch.conf -compact
145.It Pa /etc/networks
146.It Pa /etc/nsswitch.conf
147.It Pa /etc/resolv.conf
148.El
149.Sh SEE ALSO
150.Xr networks 5
151.Pp
152.%T RFC 1101
153.Sh HISTORY
154The
155.Fn getnetent ,
156.Fn getnetbyaddr ,
157.Fn getnetbyname ,
158.Fn setnetent ,
159and
160.Fn endnetent
161functions appeared in
162.Bx 4.2 .
163.Sh BUGS
164The data space used by
165these functions is thread-specific; if future use requires the data, it should be
166copied before any subsequent calls to these functions overwrite it.
167Only Internet network
168numbers are currently understood.
169Expecting network numbers to fit
170in no more than 32 bits is probably
171naive.
172