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Linux 2.6 - man page for getpwent (linux section 3posix)

ENDPWENT(P)			    POSIX Programmer's Manual			      ENDPWENT(P)

       endpwent, getpwent, setpwent - user database functions

       #include <pwd.h>

       void endpwent(void);
       struct passwd *getpwent(void);
       void setpwent(void);

       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 con-
       taining 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

       An  implementation that provides extended security controls may impose further implementa-
       tion-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  com-

       These  functions need not be reentrant. A function that is not required to be reentrant is
       not required to be thread-safe.

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

       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.

   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) {


       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 getp-
       wuid() whenever possible because it avoids these dependencies.



       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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				      ENDPWENT(P)

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