TCGETWINSIZE(3)        FreeBSD Library Functions Manual        TCGETWINSIZE(3)

NAME
     tcgetwinsize, tcsetwinsize - get, set the size of a terminal window

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <termios.h>

     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 */
     };

     int
     tcgetwinsize(int fd, struct winsize *w);

     int
     tcsetwinsize(int fd, const struct winsize *w);

DESCRIPTION
     The tcgetwinsize() function gets the terminal window size of the terminal
     of which fd is an open file descriptor and stores it in the winsize
     structure of which w is a pointer.

     The tcsetwinsize() function sets the terminal window size of the terminal
     of which fd is an open file descriptor from the winsize structure
     referenced by 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 tcsetwinsize() call, then
     the SIGWINCH signal is sent to all those members of the foreground
     process group of the terminal that have the terminal as their controlling
     terminal.

     The above declaration of struct winsize may not be literal.  It is
     provided only to list the accessible members.  Therefore, before calling
     tcsetwinsize(), the members of the winsize structure must be initialized
     by calling tcgetwinsize().  The information in a winsize structure is
     stored by the kernel in order to provide a consistent interface, but it
     is not used by the kernel.

RETURN VALUE
     The tcgetwinsize() and tcsetwinsize() functions return the value 0 if
     successful; otherwise the value -1 is returned and the global variable
     errno is set to indicate the error.  The terminal window size remains
     unchanged if tcsetwinsize() fails.

ERRORS
     The following are the possible failure conditions:

     [EBADF]            The fd argument to tcgetwinsize() or to tcsetwinsize()
                        is not a valid file descriptor.

     [ENOTTY]           The fd argument to tcgetwinsize() or to tcsetwinsize()
                        is not associated with a character special device.

     [EINVAL]           The w argument to tcsetwinsize() is not valid.

     [EFAULT]           The w argument to tcgetwinsize() or to tcsetwinsize()
                        points outside the process's allocated address space.

SEE ALSO
     stty(1), ioctl(2), sigaction(2), termios(4), tty(4)

STANDARDS
     The tcgetwinsize() and tcsetwinsize() functions are expected to conform
     to IEEE Std 1003.1 ("POSIX.1") Base Specifications, Issue 8.  The
     ws_xpixel and ws_ypixel members of struct winsize are FreeBSD extensions.

FreeBSD 13.1-RELEASE-p6        December 28, 2020       FreeBSD 13.1-RELEASE-p6