функции сетевой базы данных (network database functions)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
endnetent, getnetbyaddr, getnetbyname, getnetent, setnetent —
network database functions
Синопсис (Synopsis)
#include <netdb.h>
void endnetent(void);
struct netent *getnetbyaddr(uint32_t net, int type);
struct netent *getnetbyname(const char *name);
struct netent *getnetent(void);
void setnetent(int stayopen);
Описание (Description)
These functions shall retrieve information about networks. This
information is considered to be stored in a database that can be
accessed sequentially or randomly. The implementation of this
database is unspecified.
The setnetent() function shall open and rewind the database. If
the stayopen argument is non-zero, the connection to the net
database shall not be closed after each call to getnetent()
(either directly, or indirectly through one of the other
getnet*() functions), and the implementation may maintain an open
file descriptor to the database.
The getnetent() function shall read the next entry of the
database, opening and closing a connection to the database as
necessary.
The getnetbyaddr() function shall search the database from the
beginning, and find the first entry for which the address family
specified by type matches the n_addrtype member and the network
number net matches the n_net member, opening and closing a
connection to the database as necessary. The net argument shall
be the network number in host byte order.
The getnetbyname() function shall search the database from the
beginning and find the first entry for which the network name
specified by name matches the n_name member, opening and closing
a connection to the database as necessary.
The getnetbyaddr(), getnetbyname(), and getnetent() functions
shall each return a pointer to a netent structure, the members of
which shall contain the fields of an entry in the network
database.
The endnetent() function shall close the database, releasing any
open file descriptor.
These functions need not be thread-safe.
Возвращаемое значение (Return value)
Upon successful completion, getnetbyaddr(), getnetbyname(), and
getnetent() shall return a pointer to a netent structure if the
requested entry was found, and a null pointer if the end of the
database was reached or the requested entry was not found.
Otherwise, a null pointer shall be returned.
The application shall not modify the structure to which the
return value points, nor any storage areas pointed to by pointers
within the structure. The returned pointer, and pointers within
the structure, might be invalidated or the structure or the
storage areas might be overwritten by a subsequent call to
getnetbyaddr(), getnetbyname(), or getnetent(). The returned
pointer, and pointers within the structure, might also be
invalidated if the calling thread is terminated.
Ошибки (Error)
No errors are defined.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
None.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
The Base Definitions volume of POSIX.1‐2017, netdb.h(0p)
