tcgetsid() is defined in <termios.h>, not <sys/types.h> or <unistd.h>.

lib/libc/termios/tcgetsid.3

@@ -1,4 +1,4 @@
-.\"	$NetBSD: tcgetsid.3,v 1.5 2003/08/07 16:44:13 agc Exp $
+.\"	$NetBSD: tcgetsid.3,v 1.6 2019/12/19 16:12:21 leot Exp $
 .\"
 .\" Copyright (c) 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -29,7 +29,7 @@
 .\"
 .\"	@(#)tcgetpgrp.3	8.1 (Berkeley) 6/4/93
 .\"
-.Dd February 13, 1998
+.Dd December 19, 2019
 .Dt TCGETSID 3
 .Os
 .Sh NAME
@@ -38,8 +38,7 @@
 .Sh LIBRARY
 .Lb libc
 .Sh SYNOPSIS
-.In sys/types.h
-.In unistd.h
+.In termios.h
 .Ft pid_t
 .Fn tcgetsid "int fd"
 .Sh DESCRIPTION