xref: /openbsd-src/lib/libc/net/getnetent.3 (revision f8a44a6719aa6bcd7aba4e8f0e15ce703efdbf15)

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.Dd $Mdocdate: August 30 2019 $
.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 getnetbyname
and
.Fn getnetbyaddr
functions return a pointer to an object with the following structure:
.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; it is always
.Dv AF_INET .
.It Fa n_net
The network number.
Network numbers are returned in machine byte order.
.El
.Pp
On
.Ox ,
these legacy functions perform a lookup in a similar fashion as
.Xr gethostbyname 3
and
.Xr gethostbyaddr 3 ,
respectively.
On other systems, they may use a separate network database file,
.Pa /etc/networks .
.Pp
In contrast to
.Xr gethostbyaddr 3 ,
the
.Fa net
argument is expected in machine byte order.
.Pp
The
.Fn setnetent ,
.Fn getnetent ,
and
.Fn endnetent
functions are deprecated and no longer have any effect.
They could be used in the past to iterate over entries in the former file
.Pa /etc/networks .
.Sh RETURN VALUES
The
.Fn getnetbyaddr
and
.Fn getnetbyname
functions return
.Dv NULL
if the requested entry is not found.
.Pp
The
.Fn getnetent
function always returns
.Dv NULL .
.Sh FILES
.Bl -tag -width /etc/hosts -compact
.It Pa /etc/hosts
The local host and network name database.
.El
.Sh SEE ALSO
.Xr getaddrinfo 3 ,
.Xr gethostbyname 3 ,
.Xr getnameinfo 3 ,
.Xr res_init 3 ,
.Xr hosts 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.