getnetbyaddr(3)
NAME
getnetent, getnetbyname, getnetbyaddr, setnetent, endnetent - get network entry
SYNOPSIS
#include <netdb.h> struct netent *getnetent(void); struct netent *getnetbyname(const char *name); struct netent *getnetbyaddr(uint32_t net, int type); void setnetent(int stayopen); void endnetent(void);
DESCRIPTION
The getnetent() function reads the next entry from the networks
database and returns a netent structure containing the broken-out
fields from the entry. A connection is opened to the database if
necessary.
The getnetbyname() function returns a netent structure for the entry
from the database that matches the network name.
The getnetbyaddr() function returns a netent structure for the entry
from the database that matches the network number net of type type.
The net argument must be in host byte order.
The setnetent() function opens a connection to the database, and sets
the next entry to the first entry. If stayopen is nonzero, then the
connection to the database will not be closed between calls to one of
the getnet*() functions.
The endnetent() function closes the connection to the database.
The netent structure is defined in <netdb.h> as follows:
struct netent {
char *n_name; /* official network name */
char **n_aliases; /* alias list */
int n_addrtype; /* net address type */
uint32_t n_net; /* network number */
}
The members of the netent structure are:
n_name The official name of the network.
n_aliases
A NULL-terminated list of alternative names for the network.
n_addrtype
The type of the network number; always AF_INET.
n_net The network number in host byte order.
RETURN VALUE
The getnetent(), getnetbyname() and getnetbyaddr() functions return a pointer to a statically allocated netent structure, or a null pointer if an error occurs or the end of the file is reached.
FILES
/etc/networks
networks database file
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7). ┌───────────────┬───────────────┬───────────────────────────┐ │Interface │ Attribute │ Value │ ├───────────────┼───────────────┼───────────────────────────┤ │getnetent() │ Thread safety │ MT-Unsafe race:netent │ │ │ │ race:netentbuf env locale │ ├───────────────┼───────────────┼───────────────────────────┤ │getnetbyname() │ Thread safety │ MT-Unsafe race:netbyname │ │ │ │ env locale │ ├───────────────┼───────────────┼───────────────────────────┤ │getnetbyaddr() │ Thread safety │ MT-Unsafe race:netbyaddr │ │ │ │ locale │ ├───────────────┼───────────────┼───────────────────────────┤ │setnetent(), │ Thread safety │ MT-Unsafe race:netent env │ │endnetent() │ │ locale │ └───────────────┴───────────────┴───────────────────────────┘ In the above table, netent in race:netent signifies that if any of the functions setnetent(), getnetent(), or endnetent() are used in parallel in different threads of a program, then data races could occur.
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, 4.3BSD.
NOTES
In glibc versions before 2.2, the net argument of getnetbyaddr() was of type long.
SEE ALSO
getnetent_r(3), getprotoent(3), getservent(3) RFC 1101
COLOPHON
This page is part of release 4.09 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
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