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.\"     @(#)getprotoent.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: head/lib/libc/net/getprotoent.3 243156 2012-11-16 15:02:35Z kevlo $
.\"
.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 LIBRARY
.Lb libc
.Sh SYNOPSIS
.In netdb.h
.Ft struct protoent *
.Fn getprotoent void
.Ft struct protoent *
.Fn getprotobyname "const 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 data base,
.Pa /etc/protocols .
.Bd -literal -offset indent
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 data base 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
function
and
.Fn getprotobynumber
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 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 thread-specific 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.