групповые функции записи в базе данных (group database entry 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)
endgrent, getgrent, setgrent — group database entry functions
Синопсис (Synopsis)
#include <grp.h>
void endgrent(void);
struct group *getgrent(void);
void setgrent(void);
Описание (Description)
The getgrent() function shall return a pointer to a structure
containing the broken-out fields of an entry in the group
database. If the group database is not already open, getgrent()
shall open it and return a pointer to a group structure
containing the first entry in the database. Thereafter, it shall
return a pointer to a group structure containing the next group
structure in the group database, so successive calls may be used
to search the entire database.
An implementation that provides extended security controls may
impose further implementation-defined restrictions on accessing
the group database. In particular, the system may deny the
existence of some or all of the group database entries associated
with groups other than those groups associated with the caller
and may omit users other than the caller from the list of members
of groups in database entries that are returned.
The setgrent() function shall rewind the group database so that
the next getgrent() call returns the first entry, allowing
repeated searches.
The endgrent() function shall close the group database.
The setgrent() and endgrent() functions shall not change the
setting of errno if successful.
On error, the setgrent() and endgrent() functions shall set errno
to indicate the error.
Since no value is returned by the setgrent() and endgrent()
functions, an application wishing to check for error situations
should set errno to 0, then call the function, then check errno.
These functions need not be thread-safe.
Возвращаемое значение (Return value)
On successful completion, getgrent() shall return a pointer to a
group structure. On end-of-file, getgrent() shall return a null
pointer and shall not change the setting of errno. On error,
getgrent() shall return a null pointer and errno shall be set to
indicate the error.
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
getgrgid(), getgrnam(), or getgrent(). The returned pointer, and
pointers within the structure, might also be invalidated if the
calling thread is terminated.
Ошибки (Error)
These functions may fail if:
EINTR A signal was caught during the operation.
EIO An I/O error has occurred.
In addition, the getgrent() and setgrent() functions may fail if:
EMFILE All file descriptors available to the process are
currently open.
ENFILE The maximum allowable number of files is currently open in
the system.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
These functions are provided due to their historical usage.
Applications should avoid dependencies on fields in the group
database, whether the database is a single file, or where in the
file system name space the database resides. Applications should
use getgrnam() and getgrgid() whenever possible because it avoids
these dependencies.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
endpwent(3p), getgrgid(3p), getgrnam(3p), getlogin(3p)
The Base Definitions volume of POSIX.1‐2017, grp.h(0p)
