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.\" Copyright (c) 1997 Peter Wemm <peter@FreeBSD.org>
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.\" $FreeBSD: release/9.1.0/lib/libc/sys/getsid.2 108028 2002-12-18 09:22:32Z ru $
.\"
.Dd August 19, 1997
.Dt GETSID 2
.Os
.Sh NAME
.Nm getsid
.Nd get process session
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In 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
.Fn getsid
system call
returns the session ID of
the specified process; otherwise, it returns a value of -1 and
sets errno to indicate an error.
.Sh ERRORS
The
.Fn getsid
system call
will succeed unless:
.Bl -tag -width Er
.It Bq Er ESRCH
if there is no process with a process ID equal to
.Fa pid .
.El
.Pp
Note that an implementation may restrict this system call to
processes within the same session ID as the calling process.
.Sh SEE ALSO
.Xr getpgid 2 ,
.Xr getpgrp 2 ,
.Xr setpgid 2 ,
.Xr setsid 2 ,
.Xr termios 4
.Sh HISTORY
The
.Fn getsid
system call appeared in
.Fx 3.0 .
The
.Fn getsid
system call is derived from its usage in
.At V .