NAME
getservent,
getservent_r, getservbyport,
getservbyport_r,
getservbyname,
getservbyname_r, setservent,
setservent_r, endservent,
endservent_r —
get service entry
SYNOPSIS
#include
<netdb.h>
struct servent *
getservent(void);
int
getservent_r(struct
servent *servent, struct
servent_data *servent_data);
struct servent *
getservbyname(const
char *name, const char
*proto);
int
getservbyname_r(const
char *name, const char
*proto, struct servent
*servent, struct
servent_data *servent_data);
struct servent *
getservbyport(int
port, const char
*proto);
int
getservbyport_r(int
port, const char
*proto, struct servent
*servent, struct
servent_data *servent_data);
void
setservent(int
stayopen);
void
setservent_r(int
stayopen, struct
servent_data *servent_data);
void
endservent(void);
void
endservent_r(struct
servent_data *servent_data);
DESCRIPTION
The
getservent(),
getservbyname(), and
getservbyport() functions each return a pointer to
an object with the following structure containing the broken-out fields of a
line in the network services database,
/etc/services.
struct servent {
char *s_name; /* official name of service */
char **s_aliases; /* alias list */
int s_port; /* port service resides at */
char *s_proto; /* protocol to use */
};
The members of this structure are:
- s_name
- The official name of the service.
- s_aliases
- A null-terminated list of alternate names for the service.
- s_port
- The port number at which the service resides. Port numbers are returned in network byte order.
- s_proto
- The name of the protocol to use when contacting the service.
The
getservent()
function reads the next line of the file, opening the file if necessary.
The
setservent()
function opens and rewinds the file. If the stayopen
flag is non-zero, the services database will not be closed after each call
to getservbyname() or
getservbyport().
The
endservent()
function closes the file.
The
getservbyname()
and
getservbyport()
functions sequentially search from the beginning of the file until a
matching protocol name or port number (specified in network byte order) is
found, or until EOF is encountered. If a protocol
name is also supplied (non-null), searches must also match the protocol.
The
getservent_r(),
getservbyport_r(),
getservbyname_r(),
setservent_r(),
and
endservent_r()
functions are reentrant versions of the above functions that take a pointer
to a servent_data structure which is used to store
state information. The structure must be zero-filled before it is used and
should be considered opaque for the sake of portability.
The
getservent_r(),
getservbyport_r(),
and
getservbyname_r()
functions also take a pointer to a servent structure
which is used to store the results of the database lookup.
RETURN VALUES
The getservent(),
getservbyport(), and
getservbyname() functions return a pointer to a
servent structure on success or a null pointer if
end-of-file is reached or an error occurs.
The getservent_r(),
getservbyport_r(), and
getservbyname_r() functions return 0 on success or
-1 if end-of-file is reached or an error occurs.
FILES
- /etc/services
SEE ALSO
STANDARDS
The getservent(),
getservbynumber(),
getservbyname(),
setservent(), and
endservent() functions conform to
IEEE Std 1003.1-2004 (“POSIX.1”).
The getservent_r(),
getservbyport_r(),
getservbyname_r(),
setservent_r(), and
endservent_r() functions are not currently
standardized. This implementation follows the API used by HP, IBM, and
Digital.
HISTORY
The getservent(),
getservbyport(),
getservbyname(),
setservent(), and
endservent() functions appeared in
4.2BSD.
The getservent_r(),
getservbyport_r(),
getservbyname_r(),
setservent_r(), and
endservent_r() functions appeared in
OpenBSD 3.7.
BUGS
The non-reentrant functions use static data storage; if the data is needed for future use, it should be copied before any subsequent calls overwrite it. Expecting port numbers to fit in a 32-bit quantity is probably naive.