ENDPWENT(3)                POSIX Programmer's Manual               ENDPWENT(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.


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 .



IEEE/The Open Group                  2013                          ENDPWENT(3)
