NAME
getservent,
getservent_r, getservbyport,
getservbyport_r,
getservbyname,
getservbyname_r, setservent,
endservent —
get service entry
LIBRARY
library “libc”
SYNOPSIS
#include
<netdb.h>
struct servent *
getservent(void);
int
getservent_r(struct
servent *, char *,
size_t,
struct servent **);
struct servent *
getservbyname(const
char *name, const char
*proto);
int
getservbyname_r(const
char *, const char
*, struct servent
*, char *,
size_t,
struct servent **);
struct servent *
getservbyport(int
port, const char
*proto);
int
getservbyport_r(int,
const char *,
struct servent *,
char *,
size_t,
struct servent **);
void
setservent(int
stayopen);
void
endservent(void);
DESCRIPTION
Thegetservent(),
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 data base, /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 zero 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 net data base 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 (which must be 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(),
and
getservbyname_r()
functions are reentrant versions of the above functions that take a pointer
to a servent 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. These functions also take
a pointer to another 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(),
getservbyport(),
getservbyname(),
setservent(), and
endservent() functions conform to
IEEE Std 1003.1-2004 (“POSIX.1”).
The getservent_r(),
getservbyport_r(), and
getservbyname_r() functions are not currently
standardized.
HISTORY
The getservent(),
getservbyport(),
getservbyname(),
setservent(), and
endservent() functions appeared in
4.2BSD.
The getservent_r(),
getservbyport_r(), and
getservbyname_r() functions appeared in
DragonFly 2.1.
BUGS
These functions use a thread-specific 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.