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ENDPWENT(3P)               POSIX Programmer's Manual              ENDPWENT(3P)
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.
NAME
       endpwent, getpwent, setpwent -- user database functions
SYNOPSIS
       #include <pwd.h>
       void endpwent(void);
       struct passwd *getpwent(void);
       void setpwent(void);
DESCRIPTION
       These functions shall retrieve information about users.
       The getpwent() function shall return a pointer to a structure  contain-
       ing  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 data-
       base.  In  particular, the system may deny the existence of some or all
       of the user database entries associated with users other than the call-
       er.
       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 thread-safe.
RETURN VALUE
       The  getpwent()  function shall return a null pointer on end-of-file or
       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 getpwuid(),  getpwnam(),  or  getp-
       went().
ERRORS
       These functions may fail if:
       EIO    An I/O error has occurred.
       In addition, getpwent() and setpwent() 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.
EXAMPLES
   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>
           #include <stdio.h>
           void printname(uid_t uid)
           {
               struct passwd *pwd;
               setpwent();
               while((pwd = getpwent()) != NULL) {
                   if (pwd->pw_uid == uid) {
                       printf("name=%s\n",pwd->pw_name);
                       break;
                   }
               }
               endpwent();
           }
APPLICATION USAGE
       These functions are provided due to their historical  usage.   Applica-
       tions  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.
SEE ALSO
       endgrent(), getlogin(), getpwnam(), getpwuid()
       The Base Definitions volume of POSIX.1-2008, <pwd.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) 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.unix.org/online.html .
       Any  typographical  or  formatting  errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files  to  man page format. To report such errors, see https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                         ENDPWENT(3P)