функции базы данных учета пользователей (user accounting 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)
endutxent, getutxent, getutxid, getutxline, pututxline, setutxent
— user accounting database functions
Синопсис (Synopsis)
#include <utmpx.h>
void endutxent(void);
struct utmpx *getutxent(void);
struct utmpx *getutxid(const struct utmpx *id);
struct utmpx *getutxline(const struct utmpx *line);
struct utmpx *pututxline(const struct utmpx *utmpx);
void setutxent(void);
Описание (Description)
These functions shall provide access to the user accounting
database.
The getutxent() function shall read the next entry from the user
accounting database. If the database is not already open, it
shall open it. If it reaches the end of the database, it shall
fail.
The getutxid() function shall search forward from the current
point in the database. If the ut_type value of the utmpx
structure pointed to by id is BOOT_TIME, OLD_TIME, or NEW_TIME,
then it shall stop when it finds an entry with a matching ut_type
value. If the ut_type value is INIT_PROCESS, LOGIN_PROCESS,
USER_PROCESS, or DEAD_PROCESS, then it shall stop when it finds
an entry whose type is one of these four and whose ut_id member
matches the ut_id member of the utmpx structure pointed to by id.
If the end of the database is reached without a match, getutxid()
shall fail.
The getutxline() function shall search forward from the current
point in the database until it finds an entry of the type
LOGIN_PROCESS or USER_PROCESS which also has a ut_line value
matching that in the utmpx structure pointed to by line. If the
end of the database is reached without a match, getutxline()
shall fail.
The getutxid() or getutxline() function may cache data. For this
reason, to use getutxline() to search for multiple occurrences,
the application shall zero out the static data after each
success, or getutxline() may return a pointer to the same utmpx
structure.
There is one exception to the rule about clearing the structure
before further reads are done. The implicit read done by
pututxline() (if it finds that it is not already at the correct
place in the user accounting database) shall not modify the
static structure returned by getutxent(), getutxid(), or
getutxline(), if the application has modified this structure and
passed the pointer back to pututxline().
For all entries that match a request, the ut_type member
indicates the type of the entry. Other members of the entry shall
contain meaningful data based on the value of the ut_type member
as follows:
┌───────────────┬─────────────────────────────────────────────────────────────────┐
│ut_type Member │ Other Members with Meaningful Data │
├───────────────┼─────────────────────────────────────────────────────────────────┤
│EMPTY │ No others │
│BOOT_TIME │ ut_tv │
│OLD_TIME │ ut_tv │
│NEW_TIME │ ut_tv │
│USER_PROCESS │ ut_id, ut_user (login name of the user), ut_line, ut_pid, ut_tv │
│INIT_PROCESS │ ut_id, ut_pid, ut_tv │
│LOGIN_PROCESS │ ut_id, ut_user (implementation-defined name of the login │
│ │ process), ut_line, ut_pid, ut_tv │
│DEAD_PROCESS │ ut_id, ut_pid, ut_tv │
└───────────────┴─────────────────────────────────────────────────────────────────┘
An implementation that provides extended security controls may
impose implementation-defined restrictions on accessing the user
accounting database. In particular, the system may deny the
existence of some or all of the user accounting database entries
associated with users other than the caller.
If the process has appropriate privileges, the pututxline()
function shall write out the structure into the user accounting
database. It shall search for a record as if by getutxid() that
satisfies the request. If this search succeeds, then the entry
shall be replaced. Otherwise, a new entry shall be made at the
end of the user accounting database.
The endutxent() function shall close the user accounting
database.
The setutxent() function shall reset the input to the beginning
of the database. This should be done before each search for a new
entry if it is desired that the entire database be examined.
These functions need not be thread-safe.
Возвращаемое значение (Return value)
Upon successful completion, getutxent(), getutxid(), and
getutxline() shall return a pointer to a utmpx structure
containing a copy of the requested entry in the user accounting
database. Otherwise, a null pointer shall be returned.
The return value may point to a static area which is overwritten
by a subsequent call to getutxid() or getutxline().
Upon successful completion, pututxline() shall return a pointer
to a utmpx structure containing a copy of the entry added to the
user accounting database. Otherwise, a null pointer shall be
returned.
The endutxent() and setutxent() functions shall not return a
value.
Ошибки (Error)
No errors are defined for the endutxent(), getutxent(),
getutxid(), getutxline(), and setutxent() functions.
The pututxline() function may fail if:
EPERM The process does not have appropriate privileges.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
The sizes of the arrays in the structure can be found using the
sizeof operator.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
The Base Definitions volume of POSIX.1‐2017, utmpx.h(0p)
