.\"	$OpenBSD: getsid.2,v 1.9 2003/02/21 09:14:37 jmc Exp $
.\"
.\" Copyright (c) 1997 Peter Wemm <peter@freebsd.org>
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.Dd August 19, 1997
.Dt GETSID 2
.Os
.Sh NAME
.Nm getsid
.Nd get process session
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft pid_t
.Fn getsid "pid_t pid"
.Sh DESCRIPTION
The session ID of the process identified by
.Fa pid
is returned by
.Fn getsid .
If
.Fa pid
is zero,
.Fn getsid
returns the session ID of the current process.
.Sh RETURN VALUES
Upon successful completion, the function
.Fn getsid
returns the session ID of
the specified process; otherwise, it returns a value of \-1 and
sets
.Va errno
to indicate an error.
.Sh ERRORS
.Fn getsid
will succeed unless:
.Bl -tag -width Er
.It Bq Er EPERM
The current process and the process
.Fa pid
are not in the same session.
.It Bq Er ESRCH
There is no process with a process ID equal to
.Fa pid .
.El
.Sh SEE ALSO
.Xr getpgid 2 ,
.Xr getpgrp 2 ,
.Xr setpgid 2 ,
.Xr setsid 2 ,
.Xr termios 4
.Sh HISTORY
The
.Fn getsid
function call is derived from its usage in
.At V ,
and is mandated by
.St -xpg4 .