функции базы данных сетевых служб (network services 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)
endservent, getservbyname, getservbyport, getservent, setservent
— network services database functions
Синопсис (Synopsis)
#include <netdb.h>
void endservent(void);
struct servent *getservbyname(const char *name, const char *proto);
struct servent *getservbyport(int port, const char *proto);
struct servent *getservent(void);
void setservent(int stayopen);
Описание (Description)
These functions shall retrieve information about network
services. 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 setservent() function shall open a connection to the
database, and set the next entry to the first entry. If the
stayopen argument is non-zero, the net database shall not be
closed after each call to the getservent() function (either
directly, or indirectly through one of the other getserv*()
functions), and the implementation may maintain an open file
descriptor for the database.
The getservent() function shall read the next entry of the
database, opening and closing a connection to the database as
necessary.
The getservbyname() function shall search the database from the
beginning and find the first entry for which the service name
specified by name matches the s_name member and the protocol name
specified by proto matches the s_proto member, opening and
closing a connection to the database as necessary. If proto is a
null pointer, any value of the s_proto member shall be matched.
The getservbyport() function shall search the database from the
beginning and find the first entry for which the port specified
by port matches the s_port member and the protocol name specified
by proto matches the s_proto member, opening and closing a
connection to the database as necessary. If proto is a null
pointer, any value of the s_proto member shall be matched. The
port argument shall be a value obtained by converting a uint16_t
in network byte order to int.
The getservbyname(), getservbyport(), and getservent() functions
shall each return a pointer to a servent structure, the members
of which shall contain the fields of an entry in the network
services database.
The endservent() function shall close the database, releasing any
open file descriptor.
These functions need not be thread-safe.
Возвращаемое значение (Return value)
Upon successful completion, getservbyname(), getservbyport(), and
getservent() return a pointer to a servent 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 is 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
getservbyname(), getservbyport(), or getservent(). 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)
The port argument of getservbyport() need not be compatible with
the port values of all address families.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
endhostent(3p), endprotoent(3p), htonl(3p), inet_addr(3p)
The Base Definitions volume of POSIX.1‐2017, netdb.h(0p)
