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

       endgrent, getgrent, setgrent — group database entry functions

SYNOPSIS

       #include <grp.h>

       void endgrent(void);
       struct group *getgrent(void);
       void setgrent(void);

DESCRIPTION

       The  getgrent()  function  shall return a pointer to a structure containing the broken-out
       fields of an entry in the group database. When first called,  getgrent()  shall  return  a
       pointer to a group structure containing the first entry in the group database. Thereafter,
       it shall return a pointer to a group structure containing the next group structure in  the
       group database, so successive calls may be used to search the entire database.

       An   implementation   that   provides   extended  security  controls  may  impose  further
       implementation-defined restrictions on accessing the group database.  In  particular,  the
       system may deny the existence of some or all of the group database entries associated with
       groups other than those groups associated with the caller and may omit  users  other  than
       the caller from the list of members of groups in database entries that are returned.

       The setgrent() function shall rewind the group database to allow repeated searches.

       The  endgrent()  function  may  be  called  to close the group database when processing is
       complete.

       These functions need not be thread-safe.

RETURN VALUE

       When first called, getgrent() shall return a pointer to the first group structure  in  the
       group  database.  Upon  subsequent  calls  it shall return the next group structure in the
       group database. The getgrent() function shall return a null pointer on end-of-file  or  an
       error and errno may 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 getgrgid(), getgrnam(), or getgrent().

ERRORS

       The getgrent() function may fail if:

       EINTR  A signal was caught during the operation.

       EIO    An I/O error has occurred.

       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

       None.

APPLICATION USAGE

       These functions are provided due to their historical  usage.   Applications  should  avoid
       dependencies  on  fields  in the group database, whether the database is a single file, or
       where in the file  system  name  space  the  database  resides.  Applications  should  use
       getgrnam() and getgrgid() whenever possible because it avoids these dependencies.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       endpwent(), getgrgid(), getgrnam(), getlogin()

       The Base Definitions volume of POSIX.1‐2008, <grp.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 .