PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

SETSID(3P)                POSIX Programmer's Manual               SETSID(3P)

PROLOG         top

       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.

NAME         top

       setsid — create session and set process group ID

SYNOPSIS         top

       #include <unistd.h>

       pid_t setsid(void);

DESCRIPTION         top

       The setsid() function shall create a new session, if the calling
       process is not a process group leader. Upon return 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         top

       Upon successful completion, setsid() shall return the value of the
       new process group ID of the calling process. Otherwise, it shall
       return −1 and set errno to indicate the error.

ERRORS         top

       The setsid() function shall 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.

       The following sections are informative.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       None.

RATIONALE         top

       The setsid() function is similar to the setpgrp() function of System
       V.  System V, without job control, groups processes into process
       groups and creates new process groups via setpgrp(); only one process
       group may be part of a login session.

       Job control allows multiple process groups within a login session. In
       order to limit job control actions so that they can only affect
       processes in the same login session, this volume of POSIX.1‐2008 adds
       the concept of a session that is created via setsid().  The setsid()
       function also creates the initial process group contained in the
       session. Additional process groups can be created via the setpgid()
       function. A System V process group would correspond to a POSIX System
       Interfaces session containing a single POSIX process group. Note that
       this function requires that the calling process not be a process
       group leader. The usual way to ensure this is true is to create a new
       process with fork() and have it call setsid().  The fork() function
       guarantees that the process ID of the new process does not match any
       existing process group ID.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       getsid(3p), setpgid(3p), setpgrp(3p)

       The Base Definitions volume of POSIX.1‐2008, sys_types.h(0p),
       unistd.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/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                 2013                          SETSID(3P)

Pages that refer to this page: unistd.h(0p)_Exit(3p)getpgid(3p)getpgrp(3p)getpid(3p)getppid(3p)getsid(3p)kill(3p)setpgid(3p)setpgrp(3p)tcgetpgrp(3p)