NAME
getservent,
getservbyport,
getservbyname, setservent,
endservent —
get service entry
LIBRARY
library “libc”
SYNOPSIS
#include
<netdb.h>
struct servent *
getservent();
struct servent *
getservbyname(const
char *name, const char
*proto);
struct servent *
getservbyport(int
port, const char
*proto);
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 NULL terminated list of alternative names for the service.
- s_port
- The port number at which the service resides. Port numbers must be given and 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 is found, or until
EOF is encountered. If a protocol name is also
supplied (non-NULL), searches must also match the
protocol.
FILES
- /etc/services
DIAGNOSTICS
Null pointer (0) returned on EOF or
error.
SEE ALSO
HISTORY
The getservent(),
getservbyport(),
getservbyname(),
setservent(), and
endservent() functions appeared in
4.2BSD.
BUGS
These 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.