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 .