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.\"	@(#)setsid.2	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: releng/12.2/lib/libc/sys/setsid.2 314436 2017-02-28 23:42:47Z imp $
.\"
.Dd June 4, 1993
.Dt SETSID 2
.Os
.Sh NAME
.Nm setsid
.Nd create session and set process group ID
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft pid_t
.Fn setsid void
.Sh DESCRIPTION
The
.Fn setsid
system call creates a new session.
The calling process is the session leader of the new session, is the
process group leader of a new process group and has no controlling
terminal.
The calling process is the only process in either the session or the
process group.
.Sh RETURN VALUES
Upon successful completion, the
.Fn setsid
system call returns the value of the process group ID of the new process
group, which is the same as the process ID of the calling process.
If an error occurs,
.Fn setsid
returns -1 and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
The
.Fn setsid
system call will fail if:
.Bl -tag -width Er
.It Bq Er 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.
.El
.Sh SEE ALSO
.Xr setpgid 2 ,
.Xr tcgetpgrp 3 ,
.Xr tcsetpgrp 3
.Sh STANDARDS
The
.Fn setsid
system call is expected to be compliant with the
.St -p1003.1-90
specification.