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                                       GETPGID(3POSIX)

       The getpgid() function shall return the process group ID of the process whose process ID is equal to pid.
       If pid is equal to 0, getpgid() shall return the process group ID of the calling process.

       The getpgid() function shall fail if:

       EPERM  The process whose process ID is equal to pid is not in the same session as  the  calling  process,
              and  the  implementation  does  not  allow access to the process group ID of that process from the
              calling process.

       ESRCH  There is no process with a process ID equal to pid.

       The getpgid() function may fail if:

       EINVAL The value of the pid argument is invalid.

       Thefollowingsectionsareinformative.

       None.

       None.

       getpgid — get the process group ID for a process

       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.

       None.

       Upon  successful  completion,  getpgid()  shall  return  a  process  group ID. Otherwise, it shall return
       (pid_t)-1 and set errno to indicate the error.

exec, fork(), getpgrp(), getpid(), getsid(), setpgid(), setsid()

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

       #include <unistd.h>

       pid_t getpgid(pid_t pid);