Index: lib/libc/gen/Makefile.inc
===================================================================
--- lib/libc/gen/Makefile.inc
+++ lib/libc/gen/Makefile.inc
@@ -306,6 +306,7 @@
 	tcsetattr.3 \
 	tcsetpgrp.3 \
 	tcsetsid.3 \
+	tcsetwinsize.3 \
 	time.3 \
 	times.3 \
 	timespec_get.3 \
@@ -528,6 +529,7 @@
 	tcsetattr.3 cfsetospeed.3 \
 	tcsetattr.3 cfsetspeed.3 \
 	tcsetattr.3 tcgetattr.3
+MLINKS+=tcsetwinsize.3 tcgetwinsize.3
 MLINKS+=ttyname.3 isatty.3 \
 	ttyname.3 ttyname_r.3
 MLINKS+=tzset.3 tzsetwall.3
Index: lib/libc/gen/tcsetwinsize.3
===================================================================
--- /dev/null
+++ lib/libc/gen/tcsetwinsize.3
@@ -0,0 +1,178 @@
+.\"-
+.\" Copyright (c) 2020 Soumendra Ganguly <soumendraganguly@gmail.com>
+.\"
+.\" Copyright (c) 1995-2020 The FreeBSD Project
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL [your name] OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd December 27, 2020
+.Dt TCSETWINSIZE 3
+.Os
+.Sh NAME
+.Nm tcgetwinsize ,
+.Nm tcsetwinsize
+.Nd get, set the size of a terminal window
+.Sh LIBRARY
+.Lb libc
+.Sh SYNOPSIS
+.In termios.h
+.Bd -literal
+struct winsize {
+	unsigned short	ws_row;		/* number of rows, in characters */
+	unsigned short	ws_col;		/* number of columns, in characters */
+	unsigned short	ws_xpixel;	/* horizontal size, in pixels */
+	unsigned short	ws_ypixel;	/* vertical size, in pixels */
+};
+.Ed
+.Pp
+.Ft int
+.Fn tcgetwinsize "int fd" "struct winsize *w"
+.Ft int
+.Fn tcsetwinsize "int fd" "const struct winsize *w"
+.Sh DESCRIPTION
+The
+.Fn tcgetwinsize
+function gets the terminal window size of the terminal of which
+.Fa fd
+is an open file descriptor and stores it in the
+.Fa winsize
+structure of which
+.Fa w
+is a pointer.
+.Pp
+The
+.Fn tcsetwinsize
+function sets the terminal window size of the terminal of which
+.Fa fd
+is an open file descriptor from the
+.Fa winsize
+structure referenced by
+.Fa w .
+The change occurs immediately. If the terminal window size of the terminal
+is changed successfully to have a value that is different from the value that
+it had before the
+.Fn tcsetwinsize
+call, then
+.Dv SIGWINCH
+is sent to all those members of the foreground process group of the terminal
+that have the terminal as their controlling terminal. See
+.Xr sigaction 2 .
+.Pp
+The above declaration of
+.Vt "struct winsize"
+may not be literal. It is provided only to list the accessible members.
+Therefore, before calling
+.Fn tcsetwinsize ,
+the members of the
+.Fa winsize
+structure must be initialized by calling
+.Fn tcgetwinsize
+as follows:
+.Bd -literal
+	struct winsize ws;
+
+	if (tcgetwinsize(fd, &ws) == 0) {
+		/* make necessary modifications
+		 * to documented members of ws here
+		 */
+
+		tcsetwinsize(fd, &ws);
+	}
+.Ed
+.Pp
+See
+.In sys/_winsize.h
+for the actual declaration of
+.Vt "struct winsize" .
+.Sh RETURN VALUE
+Upon successful completion, 0 is returned by these functions. Otherwise,
+-1 is returned and
+.Va errno
+is set to indicate the error. The terminal window size remains unchanged if
+.Fn tcsetwinsize
+fails.
+.Pp
+.Sh ERRORS
+The following are the possible failure conditions:
+.Bl -tag -width Er
+.It Bq Er EBADF
+The
+.Fa fd
+argument to
+.Fn tcgetwinsize
+or to
+.Fn tcsetwinsize
+is not a valid file descriptor.
+.It Bq Er ENOTTY
+The
+.Fa fd
+argument to
+.Fn tcgetwinsize
+or to
+.Fn tcsetwinsize
+is not associated with a character special device.
+.It Bq Er EINVAL
+The
+.Fa w
+argument to
+.Fn tcsetwinsize
+is not valid.
+.It Bq Er EFAULT
+The
+.Fa w
+argument to
+.Fn tcgetwinsize
+or to
+.Fn tcsetwinsize
+points outside the process's allocated address space.
+.El
+.Sh IMPLEMENTATION NOTES
+The
+.Fn tcgetwinsize
+function is a wrapper around the
+.Dv TIOCGWINSZ
+ioctl. The
+.Fn tcsetwinsize
+function is a wrapper around the
+.Dv TIOCSWINSZ
+ioctl.
+.Sh SEE ALSO
+.Xr stty 1 ,
+.Xr ioctl 2 ,
+.Xr sigaction 2 ,
+.Xr termios 4 ,
+.Xr tty 4
+.Sh STANDARDS
+The
+.Fn tcgetwinsize
+and
+.Fn tcsetwinsize
+functions are expected to conform to issue 8 of
+.St -p1003.1 .
+The standard does not specify the
+.Fa ws_xpixel
+and
+.Fa ws_ypixel
+members of
+.Vt "struct winsize" .