GETSID(2) Linux Programmer's Manual GETSID(2)
getsid - get session ID
pid_t getsid(pid_t pid);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
getsid(): _XOPEN_SOURCE >= 500
getsid(0) returns the session ID of the calling process. getsid(p)
returns the session ID of the process with process ID p. (The session
ID of a process is the process group ID of the session leader.)
On success, a session ID is returned. On error, (pid_t) -1 will be
returned, and errno is set appropriately.
EPERM A process with process ID p exists, but it is not in the same
session as the calling process, and the implementation considers
this an error.
ESRCH No process with process ID p was found.
This system call is available on Linux since version 2.0.
Linux does not return EPERM.
getpgid(2), setsid(2), credentials(7)
This page is part of release 3.22 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2008-12-05 GETSID(2)