DragonFly On-Line Manual Pages
GETSERVENT(3) DragonFly Library Functions Manual GETSERVENT(3)
NAME
getservent, getservent_r, getservbyport, getservbyport_r, getservbyname,
getservbyname_r, setservent, endservent - get service entry
LIBRARY
Standard C Library (libc, -lc)
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
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 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
getprotoent(3), services(5)
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.
DragonFly 5.5-DEVELOPMENT May 4, 2019 DragonFly 5.5-DEVELOPMENT