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.\"     @(#)getnetent.3	8.1 (Berkeley) 6/4/93
.\"
.Dd February 21, 2018
.Dt GETNETENT 3
.Os
.Sh NAME
.Nm getnetent ,
.Nm getnetbyaddr ,
.Nm getnetbyname ,
.Nm setnetent ,
.Nm endnetent
.Nd get network entry
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In netdb.h
.Ft struct netent *
.Fn getnetent
.Ft struct netent *
.Fn getnetbyname "const char *name"
.Ft struct netent *
.Fn getnetbyaddr "uint32_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
data base as described in
.Xr networks 5 .
.Bd -literal -offset indent
struct	netent {
	char		*n_name;	/* official name of net */
	char		**n_aliases;	/* alias list */
	int		n_addrtype;	/* net number type */
	uint32_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 zero terminated list of alternative 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 host 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 data base 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 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 byte order.
.Sh FILES
.Bl -tag -width /etc/networks -compact
.It Pa /etc/networks
.El
.Sh RETURN VALUES
Null pointer
.Dv ( NULL )
returned on
.Dv EOF
or error.
.Sh SEE ALSO
.Xr networks 5 ,
.Xr nsswitch.conf 5
.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 probably
naive.