O nás     Inzerce     KontaktSpolehlivé informace o IT již od roku 2011
Hledat
Nepřehlédněte: Nejlepší IT: Pozoruhodné IT produkty pro rok 2024 podruhé
Správa dokumentů
Digitální transformace
Informační systémy
Hlavní rubriky: Informační systémy, Mobilní technologie, Datová centra, Sítě, IT bezpečnost, Software, Hardware, Zkušenosti a názory, Speciály

Pozoruhodné IT produkty 2024 podruhé
E-knihy o IT zdarma
Manuál Linux
[Linux manuál]

endpwent, getpwent, setpwent: uživatelské databáze

Originální popis anglicky: endpwent, getpwent, setpwent - user database functions

Návod, kniha: POSIX Programmer's Manual

STRUČNĚ

#include <pwd.h>
 
 
void endpwent(void);
 
struct passwd *getpwent(void);
 
void setpwent(void);
 

POPIS / INSTRUKCE

These functions shall retrieve information about users.
The getpwent() function shall return a pointer to a structure containing the broken-out fields of an entry in the user database. Each entry in the user database contains a passwd structure. When first called, getpwent() shall return a pointer to a passwd structure containing the first entry in the user database. Thereafter, it shall return a pointer to a passwd structure containing the next entry in the user database. Successive calls can be used to search the entire user database.
If an end-of-file or an error is encountered on reading, getpwent() shall return a null pointer.
An implementation that provides extended security controls may impose further implementation-defined restrictions on accessing the user database. In particular, the system may deny the existence of some or all of the user database entries associated with users other than the caller.
The setpwent() function effectively rewinds the user database to allow repeated searches.
The endpwent() function may be called to close the user 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

The getpwent() function shall return a null pointer on end-of-file or error.

CHYBY / ERRORY

The getpwent(), setpwent(), and endpwent() functions may fail if:
EIO
An I/O error has occurred.
 
In addition, getpwent() and setpwent() may fail if:
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 return value may point to a static area which is overwritten by a subsequent call to getpwuid(), getpwnam(), or getpwent().
 
The following sections are informative.

PŘÍKLADY POUŽITÍ

Searching the User Database

The following example uses the getpwent() function to get successive entries in the user database, returning a pointer to a passwd structure that contains information about each user. The call to endpwent() closes the user database and cleans up.
 
#include <pwd.h> ... struct passwd *p; ... while ((p = getpwent ()) != NULL) { ... }
 
endpwent(); ...

APPLICATION USAGE

These functions are provided due to their historical usage. Applications should avoid dependencies on fields in the password database, whether the database is a single file, or where in the file system name space the database resides. Applications should use getpwuid() whenever possible because it avoids these dependencies.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SOUVISEJÍCÍ

endgrent() , getlogin() , getpwnam() , getpwuid() , the Base Definitions volume of IEEE Std 1003.1-2001, <pwd.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
©2011-2024 BusinessIT.cz, ISSN 1805-0522 | Názvy použité v textech mohou být ochrannými známkami příslušných vlastníků.
Provozovatel: Bispiral, s.r.o., kontakt: BusinessIT(at)Bispiral.com | Inzerce: Best Online Media, s.r.o., zuzana@online-media.cz
O vydavateli | Pravidla webu BusinessIT.cz a ochrana soukromí | Používáme účetní program Money S3 | pg(9049)