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.Dd June 4, 1993
.Dt GETPROTOENT 3
.Os
.Sh NAME
.Nm getprotoent ,
.Nm getprotobynumber ,
.Nm getprotobyname ,
.Nm setprotoent ,
.Nm endprotoent
.Nd get protocol entry
.Sh SYNOPSIS
.Fd #include <netdb.h>
.Ft struct protoent *
.Fn getprotoent "void"
.Ft struct protoent *
.Fn getprotobyname "char *name"
.Ft struct protoent *
.Fn getprotobynumber "int proto"
.Ft void
.Fn setprotoent "int stayopen"
.Ft void
.Fn endprotoent "void"
.Sh DESCRIPTION
The
.Fn getprotoent ,
.Fn getprotobyname ,
and
.Fn getprotobynumber
functions each return a pointer to an object with the following structure
containing the broken-out fields of a line in the network protocol database,
.Pa /etc/protocols .
.Bd -literal -offset indent
.Pp
struct	protoent {
	char	*p_name;	/* official name of protocol */
	char	**p_aliases;	/* alias list */
	int	p_proto;	/* protocol number */
};
.Ed
.Pp
The members of this structure are:
.Bl -tag -width p_aliases
.It Fa p_name
The official name of the protocol.
.It Fa p_aliases
A zero-terminated list of alternate names for the protocol.
.It Fa p_proto
The protocol number.
.El
.Pp
The
.Fn getprotoent
function reads the next line of the file, opening the file if necessary.
.Pp
The
.Fn setprotoent
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 getprotobyname
or
.Fn getprotobynumber .
.Pp
The
.Fn endprotoent
function closes the file.
.Pp
The
.Fn getprotobyname
and
.Fn getprotobynumber
functions sequentially search from the beginning of the file until a
matching protocol name or protocol number is found, or until
.Dv EOF
is encountered.
.Sh RETURN VALUES
Null pointer (0) returned on
.Dv EOF
or error.
.Sh FILES
.Bl -tag -width /etc/protocols -compact
.It Pa /etc/protocols
.El
.Sh SEE ALSO
.Xr protocols 5
.Sh HISTORY
The
.Fn getprotoent ,
.Fn getprotobynumber ,
.Fn getprotobyname ,
.Fn setprotoent ,
and
.Fn endprotoent
functions appeared in
.Bx 4.2 .
.Sh BUGS
These functions use a static data space; if the data is needed for future use,
it should be copied before any subsequent calls overwrite it.
Only the Internet protocols are currently understood.