setsid(2) [debian man page]

SETSID(2)						     Linux Programmer's Manual							 SETSID(2)

NAME

       setsid - creates a session and sets the process group ID

SYNOPSIS

       #include <unistd.h>

       pid_t setsid(void);

DESCRIPTION

       setsid() creates a new session if the calling process is not a process group leader.  The calling process is the leader of the new session,
       the process group leader of the new process group, and has no controlling tty.  The process group ID and session ID of the calling  process
       are set to the PID of the calling process.  The calling process will be the only process in this new process group and in this new session.

RETURN VALUE

       On  success,  the  (new) session ID of the calling process is returned.	On error, (pid_t) -1 is returned, and errno is set to indicate the
       error.

ERRORS

       EPERM  The process group ID of any process equals the PID of the calling process.  Thus, in  particular,  setsid()  fails  if  the  calling
	      process is already a process group leader.

CONFORMING TO

       SVr4, POSIX.1-2001.

NOTES

       A child created via fork(2) inherits its parent's session ID.  The session ID is preserved across an execve(2).

       A  process  group  leader is a process with process group ID equal to its PID.  In order to be sure that setsid() will succeed, fork(2) and
       _exit(2), and have the child do setsid().

SEE ALSO

       getsid(2), setpgid(2), setpgrp(2), tcgetsid(3), credentials(7)

COLOPHON

       This page is part of release 3.44 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								    2008-12-03								 SETSID(2)

setsid(2)							   System Calls 							 setsid(2)

NAME

       setsid - create session and set process group ID

SYNOPSIS

       #include <sys/types.h>
       #include <unistd.h>

       pid_t setsid(void);

DESCRIPTION

       The  setsid() function creates a new session, if the calling process is not a process group leader. Upon return the calling process will be
       the session leader of this new session, will be the process group leader of a new process group, and will have no controlling terminal. The
       process	group	ID of the calling process will be set equal to the process ID of the calling process. The calling process will be the only
       process in the new process group and the only process in the new session.

RETURN VALUES

       Upon successful completion, setsid() returns the value of the process group  ID of the calling process. Otherwise it returns (pid_t)-1  and
       sets errno to indicate the error.

ERRORS

       The setsid() function will fail if:

       EPERM	The  calling  process  is  already  a  process	group leader, or the process group  ID of a process other than the calling process
		matches the process  ID of the calling process.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Async-Signal-Safe 	   |
       +-----------------------------+-----------------------------+

SEE ALSO

       getsid(2), setpgid(2), setpgrp(2), attributes(5), standards(5)

WARNINGS

       A call to setsid() by a process that is a process group leader will fail. A process can become a process group leader  by  being  the  last
       member of a pipeline started by a job control shell. Thus, a process that expects to be part of a pipeline, and that calls setsid(), should
       always first fork; the parent should exit and the child should call setsid(). This will ensure that the calling process will work  reliably
       when started by both job control shells and non-job control shells.

SunOS 5.11							    21 Aug 2002 							 setsid(2)