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

       The endgrent() function shall close the group database.

       The setgrent() and endgrent() functions shall not change the setting of errno if successful.

       On error, the setgrent() and endgrent() functions shall set errno to indicate the error.

       Since  no  value  is returned by the setgrent() and endgrent() 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.

RETURN VALUE

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

ERRORS

       These functions may fail if:

       EINTR  A signal was caught during the operation.

       EIO    An I/O error has occurred.

       In addition, the getgrent() and setgrent() functions 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

       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.1‐2017, <grp.h>

COPYRIGHT

       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                                      ENDGRENT(3POSIX)