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                                        GETSID(3POSIX)

       The  getsid() function shall obtain the process group ID of the process that is the session leader of the
       process specified by pid.  If pid is (pid_t)0, it specifies the calling process.

       The getsid() function shall fail if:

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

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

       Thefollowingsectionsareinformative.

       None.

       None.

       getsid — get the process group ID of a session leader

       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, getsid() shall return the process group ID  of  the  session  leader  of  the
       specified process. Otherwise, it shall return -1 and set errno to indicate the error.

exec, fork(), getpid(), getpgid(), setpgid(), setsid()

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

       #include <unistd.h>

       pid_t getsid(pid_t pid);