setsid(2)                      DG/UX R4.11MU05                     setsid(2)


NAME
       setsid - create session and set process group ID

SYNOPSIS
       #include <sys/types.h>

       pidt  setsid ()

DESCRIPTION
       If the calling process is not a process group leader, the setsid()
       function shall create a new session.  The calling process shall be
       the session leader of this new session, shall be the process group
       leader of a new process group, and shall have no controlling
       terminal.  The process group ID of the calling process shall be set
       equal to the process ID of the calling process.  The calling process
       shall be the only process in the new process group and the only
       process in the new session.

RETURN VALUE
       Upon successful completion, the setsid() function returns the value
       of the process group ID of the calling process.

DIAGNOSTICS
       If any of the following conditions occur, the setsid() function shall
       return -1 and set errno to the corresponding value:

       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.

SEE ALSO
       exec(2), exit(2), fork(2), getpid(2), kill(2) setpgid(2),
       sigaction(2).

COPYRIGHTS
       Portions of this text are reprinted from IEEE Std 1003.1-1988,
       Portable Operating System Interface for Computer Environment,
       copyright © 1988 by the Institute of Electrical and Electronics
       Engineers, Inc., with the permission of the IEEE Standards
       Department.  To purchase IEEE Standards, call 800/678-IEEE.

       In the event of a discrepancy between the electronic and the original
       printed version, the original version takes precedence.

STANDARDS
       The only way for a session to allocate a controlling terminal is for
       the session leader (which must not already have a controlling
       terminal) to open a terminal device that is not already associated
       with any session, without using the O_NOCTTY option to open().  The
       effect is that the processes in a session may have at most one
       controlling terminal, and a terminal may have at most one controlling
       process, which must be a session leader.  When the controlling
       process terminates, an automatic vhangup() occurs on the terminal and
       its terminal characteristics are reset.


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