man2/setsid.2

   1 .\" Copyright Michael Haardt (michael@cantor.informatik.rwth-aachen.de) Sat Aug 27 20:43:50 MET DST 1994
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  23 .\" Modified Sun Sep 11 19:19:05 1994 <faith@cs.unc.edu>
  24 .\" Modified Mon Mar 25 10:19:00 1996 <aeb@cwi.nl> (merged a few
  25 .\"     tiny changes from a man page by Charles Livingston).
  26 .\" Modified Sun Jul 21 14:45:46 1996 <aeb@cwi.nl>
  27 .\"
  28 .TH SETSID 2 1994-08-27 "Linux 1.0.0" "Linux Programmer's Manual"
  29 .SH NAME
  30 setsid \- creates a session and sets the process group ID
  31 .SH SYNOPSIS
  32 .ad l
  33 .B #include <unistd.h>
  34 .sp
  35 .B pid_t setsid(void);
  36 .br
  37 .ad b
  38 .SH DESCRIPTION
  39 \fBsetsid()\fP creates a new session if the calling process is not a
  40 process group leader.  The calling process is the leader of the new
  41 session, the process group leader of the new process group, and has no
  42 controlling tty.  The process group ID and session ID of the calling
  43 process are set to the PID of the calling process.  The calling process
  44 will be the only process in this new process group and in this new session.
  45 .SH "RETURN VALUE"
  46 The session ID of the calling process.
  47 .SH ERRORS
  48 On error, \-1 is returned, and
  49 .I errno
  50 is set.
  51 The only error which can happen is
  52 EPERM. It is returned when the process group ID of any process
  53 equals the PID of the calling process. Thus, in particular,
  54 .B setsid
  55 fails if the calling process is already a process group leader.
  56 .SH NOTES
  57 A process group leader is a process with process group ID equal
  58 to its PID. In order to be sure that
  59 .B setsid
  60 will succeed, fork and exit, and have the child do
  61 .BR setsid().
  62 .SH "CONFORMING TO"
  63 POSIX, SVr4.
  64 .SH "SEE ALSO"
  65 .BR setpgid (2),
  66 .BR setpgrp (2)