getnetent.3n (2010 09)

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getnetent(3N) getnetent(3N)

NAME

getnetent(), getnetbyaddr(), getnetbyname(), setnetent(), endnetent() - get, set, or end network entry

SYNOPSIS

#include <sys/socket.h>

#include <netdb.h>

struct netent *getnetent(void);

struct netent *getnetbyname(const char *name);

struct netent *getnetbyaddr(unsigned int net, int type);

_XOPEN_SOURCE_EXTENDED only

struct netent *getnetbyaddr(in_addr_t net, int type);

int setnetent(int stayopen);

int endnetent(void);

_XOPEN_SOURCE_EXTENDED only

void setnetent(int stayopen);

void endnetent(void);

DESCRIPTION

getnetent(), getnetbyname(), and

getnetbyaddr() each return a pointer to a structure of

type netent containing the broken-out ﬁelds of a line in the network data base,

/etc/networks

The members of this structure are:

n_name The ofﬁcial name of the network.

n_aliases A null-terminated list of alternate names for the network.

n_addrtype The type of the network number returned; always AF_INET.

n_net The network number.

Functions behave as follows:

getnetent() Reads the next line of the ﬁle, opening the ﬁle if necessary.

setnetent() Opens and rewinds the ﬁle. If the stayopen ﬂag is non-zero, the network

data base is not closed after each call to getnetent() (either directly or

indirectly through one of the other getnet* calls).

endnetent() Closes the ﬁle.

getnetbyname() Sequentially searches from the beginning of the ﬁle until a network name

(among either the ofﬁcial names or the aliases) matching its parameter

name is found, or until EOF is encountered.

getnetbyaddr() Sequentially searches from the beginning of the ﬁle until a network number

matching its parameter net is found, or until EOF is encountered. The

parameter net must be in network order. The parameter type must be the

constant AF_INET. Network numbers are supplied in host order (see

byteorder (3N)).

If the system is running Network Information Service (NFS),

getnetbyname() and getnet-

byaddr() obtain their network information from the NIS server (see ypserv (1M) and ypﬁles (4)).

In a multithreaded application,

getnetent(), getentbyaddr(), and

getentbyname() use

thread-speciﬁc storage that is re-used in each call. The return value,

struct netent, should be unique

for each thread and should be saved, if desired, before the thread makes the next getnet*() call.

For enumeration in multithreaded applications, the position within the enumeration is a process-wide

property shared by all threads.

setnetent() may be used in a multithreaded application, but resets

the enumeration position for all threads. If multiple threads interleave calls to getnetent(), the

threads will enumerate disjoint subsets of the network database.

Name Service Switch-Based Operation

The library routines

getnetbyname(), getnetbyaddr(), and getnetent() internally call the

name service switch to access the "networks" database lookup policy conﬁgured in the

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (2 pages)

PAGE 1
getnetent(3N) getnetent(3N) NAME getnetent(), getnetbyaddr(), getnetbyname(), setnetent(), endnetent() - get, set, or end network entry SYNOPSIS #include #include
PAGE 2
getnetent(3N) getnetent(3N) /etc/nsswitch.conf file (see nsswitch.conf(4)). The lookup policy defines the order and the criteria of the supported name services used to resolve network names and addresses. RETURN VALUE getnetent(), getnetbyname(), and getnetbyaddr() return a null pointer (0) on EOF or when they are unable to open /etc/networks. getnetbyaddr() also returns a null pointer if its type parameter is invalid.