.\"	$NetBSD: tcgetsid.3,v 1.5 2003/08/07 16:44:13 agc Exp $
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.\"	@(#)tcgetpgrp.3	8.1 (Berkeley) 6/4/93
.\"
.Dd February 13, 1998
.Dt TCGETSID 3
.Os
.Sh NAME
.Nm tcgetsid
.Nd get session ID associated with a controlling terminal
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/types.h
.In unistd.h
.Ft pid_t
.Fn tcgetsid "int fd"
.Sh DESCRIPTION
The
.Nm tcgetsid
function returns the value of the session ID associated with the specified
controlling terminal device.
The session ID is defined as the process group ID of the session leader.
.Sh ERRORS
If an error occurs,
.Nm tcgetsid
returns -1 and the global variable
.Va errno
is set to indicate the error, as follows:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa fd
argument is not a valid file descriptor.
.It Bq Er ENOTTY
The calling process does not have a controlling terminal or the
underlying terminal device represented by
.Fa fd
is not the controlling terminal.
.El
.Sh SEE ALSO
.Xr getsid 2 ,
.Xr setsid 2 ,
.Xr tcgetpgrp 3
.Sh STANDARDS
The
.Nm tcgetsid
function conforms to
.St -xpg4.2 .