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 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 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 getpwent().

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.   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.

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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .