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.\" Copyright (c) 2020 Soumendra Ganguly <soumendraganguly@gmail.com>
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.\" Portions of this text are reprinted and reproduced in electronic form
.\" from P1003.1-202x, Draft 1.1, Draft Standard for Information Technology --
.\" Portable Operating System Interface (POSIX), The Open Group Base
.\" Specifications Issue 8, Copyright (C) 2020 by the Institute of
.\" Electrical and Electronics Engineers, Inc and The Open Group. In the
.\" event of any discrepancy between this version and the original IEEE and
.\" The Open Group Standard, the original IEEE and The Open Group Standard is
.\" the referee document. The original Standard can be obtained online at
.\"	http://www.opengroup.org/unix/online.html.
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.\" $FreeBSD$
.\"
.Dd December 28, 2020
.Dt TCGETWINSIZE 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
.Vt 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
.Vt 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 the
.Dv SIGWINCH
signal is sent to all those members of the foreground process group of the
terminal that have the terminal as their controlling terminal.
.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
.Vt winsize
structure must be initialized by calling
.Fn tcgetwinsize .
The information in a
.Vt winsize
structure is stored by the kernel in order to provide a consistent interface,
but it is not used by the kernel.
.Sh RETURN VALUE
.Rv -std tcgetwinsize tcsetwinsize
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 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
.St -p1003.1
Base Specifications, Issue 8.
The
.Fa ws_xpixel
and
.Fa ws_ypixel
members of
.Vt "struct winsize"
are FreeBSD extensions.