This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       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.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group  Base
       Specifications  Issue  7, 2018 Edition, Copyright (C) 2018 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 .

       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 .

IEEE/The Open Group                                   2017                                      ENDPWENT(3POSIX)

       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.  If  the  user
       database  is  not  already  open,  getpwent()  shall  open  it and return a pointer to a passwd structure
       containing the first entry in the 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 shall rewind the user database so that the next getpwent() call returns the first
       entry, allowing repeated searches.

       The endpwent() function shall close the user database.

       The setpwent() and endpwent() functions shall not change the setting of errno if successful.

       On error, the setpwent() and endpwent() functions shall set errno to indicate the error.

       Since no value is returned by the setpwent() and endpwent() functions, an application  wishing  to  check
       for error situations should set errno to 0, then call the function, then check errno.

       These functions need not be thread-safe.

       These functions may fail if:

       EINTR  A signal was caught during the operation.

       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.

       Thefollowingsectionsareinformative.

SearchingtheUserDatabase
       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();
           }

       None.

       endpwent, getpwent, setpwent — user database functions

       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.

       None.

       On  successful  completion,  getpwent()  shall  return  a  pointer to a passwd structure. On end-of-file,
       getpwent() shall return a null pointer and shall not change the setting of errno.  On  error,  getpwent()
       shall return a null pointer and errno shall be set to indicate the 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().  The returned pointer, and pointers within  the  structure,  might
       also be invalidated if the calling thread is terminated.

endgrent(), getlogin(), getpwnam(), getpwuid()

       The Base Definitions volume of POSIX.1‐2017, <pwd.h>

       #include <pwd.h>

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