getprotoent.3n

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)getprotoent.3n	8.2	1/29/91
.TH getprotoent 3n
.SH Name
getprotoent, getprotobynumber, getprotobyname, setprotoent, endprotoent \- get protocols entry
.SH Syntax
.nf
.B #include <netdb.h>
.PP
.B struct protoent *getprotoent()
.PP
.B struct protoent *getprotobyname(\fIname\fP)
.B char *\fIname\fP;
.PP
.B struct protoent *getprotobynumber(\fIproto\fP)
.B int \fIproto\fP;
.PP
.B void setprotoent(\fIstayopen\fP)
.B int \fIstayopen\fP;
.PP
.B void endprotoent()
.fi
.SH Description
.NXR "getprotoent subroutine"
.NXR "getprotobyname subroutine"
.NXR "getprotobyname subroutine"
.NXR "setprotoent subroutine"
.NXR "endprotoent subroutine"
.NXR "protocols file" "getting entry"
The
.PN getprotoent ,
.PN getprotobyname ,
and
.PN getprotobynumber
subroutines
each return a pointer to an object with the
following structure
containing the broken-out
fields of a line in the 
.PN protocols
database.
.EX
struct	protoent {
	char	*p_name;	/* official name of protocol */
	char	**p_aliases;	/* alias list */
	long	p_proto;	/* protocol number */
};
.EE
.PP
The members of this structure are:
.TP \w'p_aliases'u+2n
p_name
The official name of the protocol.
.TP \w'p_aliases'u+2n
p_aliases
A zero terminated list of alternate names for the protocol.
.TP \w'p_aliases'u+2n
p_proto
The protocol number.
.PP
If the
.I stayopen
flag on a 
.PN setprotoent
subroutine is NULL, the
protocols database is opened.  Otherwise the
.PN setprotoent
has the effect of rewinding the protocols database.
The
.PN endprotoent
may be called to
close the protocols database
when processing is complete.
.PP
The
.PN getprotoent
subroutine simply reads the next
line while
.PN getprotobyname
and
.PN getprotobynumber
search until a matching
.I name
or
.I proto
number is found
(or until EOF is encountered).
The
.PN getprotoent
subroutine keeps a pointer in the database, allowing
successive calls to be used 
to search the entire file.
.PP
A call to
.PN setprotoent
must be made before a
.PN while
loop using
.PN getprotoent
in order to perform initialization and an
.PN endprotoent
must be used after the loop.  Both
.PN getprotobyname
and
.PN getprotobynumber
make calls to
.PN setprotoent
and
.PN endprotoent .
.SH Restrictions
.NXR "getprotoent subroutine" "restrictions"
All information
is contained in a static area
so it must be copied if it is
to be saved.  Only the Internet
protocols are currently understood.
.PP
.PP
If YP is running, 
.PN getprotoent
does not return the entries in any particular order.
See the 
.I Guide to the Yellow Pages Service
for setup information.
.PP
The services database may also be distributed using the BIND/Hesiod
naming service.  See the 
.I Guide to the BIND/Hesiod Service
for more information.
.SH Return Values
Null pointer
(0) returned on EOF or error.
.SH Files
.PN /etc/protocols
.SH See Also
protocols(5), svc.conf(5)
.br
.I Guide to the BIND/Hesiod Service
.br
.I Guide to the Yellow Pages Service