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

       None.

       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                                        SETGID(3POSIX)

       If  the process has appropriate privileges, setgid() shall set the real group ID, effective group ID, and
       the saved set-group-ID of the calling process to gid.

       If the process does not have appropriate privileges, but gid is equal to the real group ID or  the  saved
       set-group-ID,  setgid() shall set the effective group ID to gid; the real group ID and saved set-group-ID
       shall remain unchanged.

       The setgid() function shall not affect the supplementary group list in any way.

       Any supplementary group IDs of the calling process shall remain unchanged.

       The setgid() function shall fail if:

       EINVAL The value of the gid argument is invalid and is not supported by the implementation.

       EPERM  The  process  does not have appropriate privileges and gid does not match the real group ID or the
              saved set-group-ID.

       Thefollowingsectionsareinformative.

       None.

       None.

       setgid — set-group-ID

       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.

       Refer to the RATIONALE section in setuid().

       Upon successful completion, 0 is returned. Otherwise, -1 shall be returned and errno set to indicate  the
       error.

exec, getegid(), geteuid(), getgid(), getuid(), setegid(), seteuid(), setregid(), setreuid(), setuid()

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

       #include <unistd.h>

       int setgid(gid_t gid);