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endgrent, getgrent, setgrent: funkce pro zadávání skupinových databází

Originální popis anglicky: endgrent, getgrent, setgrent - group database entry functions

Návod, kniha: POSIX Programmer's Manual

STRUČNĚ

#include <grp.h>
 
 
void endgrent(void);
 
struct group *getgrent(void);
 
void setgrent(void);
 

POPIS / INSTRUKCE

The getgrent() function shall return a pointer to a structure containing the broken-out fields of an entry in the group database. When first called, getgrent() shall return a pointer to a group structure containing the first entry in the group 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 to allow repeated searches.
The endgrent() function may be called to close the group database when processing is complete.
These functions need not be reentrant. A function that is not required to be reentrant is not required to be thread-safe.

NÁVRATOVÁ HODNOTA

When first called, getgrent() shall return a pointer to the first group structure in the group database. Upon subsequent calls it shall return the next group structure in the group database. The getgrent() function shall return a null pointer on end-of-file or an error and errno may be set to indicate the error.
The return value may point to a static area which is overwritten by a subsequent call to getgrgid(), getgrnam(), or getgrent().

CHYBY / ERRORY

The getgrent() function may fail if:
EINTR
A signal was caught during the operation.
EIO
An I/O error has occurred.
EMFILE
{OPEN_MAX} file descriptors are currently open in the calling process.
ENFILE
The maximum allowable number of files is currently open in the system.
 
The following sections are informative.

PŘÍKLADY POUŽITÍ

None.

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.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SOUVISEJÍCÍ

getgrgid() , getgrnam() , getlogin() , getpwent() , the Base Definitions volume of IEEE Std 1003.1-2001, <grp.h> Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .
2003 IEEE/The Open Group
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