getservent.3n

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3N 代码 · 共 157 行

.\" SCCSID: @(#)getservent.3n	8.2	1/29/91
.TH getservent 3n
.SH Name
getservent, getservbyname, getservbyport, setservent, endservent \- get 
services entry
.SH Syntax
.nf
.B #include <netdb.h>
.PP
.B struct servent *getservent()
.PP
.B struct servent *getservbyname\fI(name, proto)\fP
.B char *\fIname\fP, *\fIproto\fP;
.PP
.B struct servent *getservbyport\fI(port, proto)\fP
.B int \fIport\fP; char *\fIproto\fP;
.PP
.B void setservent\fI(stayopen)\fP
.B int \fIstayopen\fP
.PP
.B void endservent()
.fi
.SH Description
.NXR "getservent subroutine"
.NXR "getservbyport subroutine"
.NXR "getservbyname subroutine"
.NXR "setservent subroutine"
.NXR "endservent subroutine"
.NXR "services file" "getting entry"
The
.PN getservent ,
.PN getservbyname ,
and
.PN getservbyport
subroutines each return a pointer to an object with the
following structure
containing the broken-out
fields of a line in the network 
.PN services 
database.
.EX
.nf
struct	servent {
	char	*s_name;        /* official name of service */
	char	**s_aliases;    /* alias list */
	long	s_port;         /* port service resides at */
	char	*s_proto;       /* protocol to use */
};
.fi
.EE
.PP
The members of this structure are:
.TP \w's_aliases'u+2n
s_name
The official name of the service.
.TP \w's_aliases'u+2n
s_aliases
A zero terminated list of alternate names for the service.
.TP \w's_aliases'u+2n
s_port
The port number at which the service resides.
Port numbers are returned in network byte order.
.TP \w's_aliases'u+2n
s_proto
The name of the protocol to use when contacting the
service.
.PP
If the 
.I stayopen
flag on a 
.PN setservent
subroutine is NULL, the
.PN services 
database is opened.  Otherwise, the
.PN setservent
has the effect of rewinding the 
.PN services 
database.
The
.PN endservent
subroutine may be called to 
close the 
.PN services 
database when processing is complete.
.PP
The
.PN getservent
subroutine reads the next
line; 
.PN getservbyname
and
.PN getservbyport
search until a matching
.I name
or
.I port
is found
(or until EOF is encountered).
The
.PN getservent
subroutine keeps a pointer in the database, allowing
successive calls to be used 
to search the entire file.
If a non-NULL protocol name,
.PN proto ,
is also supplied, searches must also match the protocol.
.PP
The
.PN setservent
routine must be called before a
.PN while
loop that uses
.PN getservent
in order to initialize variables in the
.PN setservent
routine and an
.PN endservent
must be used after the loop.  Both
.PN getservbyport
and
.PN getservbyname
make calls to
.PN setservent
and
.PN endservent .
.SH Restrictions
.NXR "getservent subroutine" "restrictions"
All information
is contained in a static area
so it must be copied if it is
to be saved.
.PP
If the Yellow Pages Service is running, 
.PN getservent
does not return the entries in any particular order.
See the 
.I Guide to the Yellow Pages Service
for setup information.
.PP
The 
.PN services 
database can also be distributed by 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/services
.SH See Also
services(5), svc.conf(5)
.br
.I Guide to the BIND/Hesiod Service
.br
.I Guide to the Yellow Pages Service