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setsid(2) [linux 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 3.27 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)

Check Out this Related Man Page

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

PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond- ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME
setsid - create session and set process group ID SYNOPSIS
#include <unistd.h> pid_t setsid(void); DESCRIPTION
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
Upon successful completion, setsid() shall return the value of the new process group ID of the calling process. Otherwise, it shall return (pid_t)-1 and set errno to indicate the error. ERRORS
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
None. APPLICATION USAGE
None. RATIONALE
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 pro- cesses in the same login session, this volume of IEEE Std 1003.1-2001 adds the concept of a session that is created via setsid(). The set- sid() 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
None. SEE ALSO
getsid(), setpgid(), setpgrp(), the Base Definitions volume of IEEE Std 1003.1-2001, <sys/types.h>, <unistd.h> COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol- ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 . IEEE
/The Open Group 2003 SETSID(3P)

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