blob: 7f03047e28a391cda259f72f67de7cd24a0f20c5 [file] [log] [blame]
// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package textutil
import (
// TerminalSize returns the dimensions of the terminal, if it's available from
// the OS, otherwise returns an error.
func TerminalSize() (row, col int, _ error) {
// Try getting the terminal size from stdout, stderr and stdin respectively.
// We try each of these in turn because the mechanism we're using fails if any
// of the fds is redirected on the command line. E.g. "tool | less" redirects
// the stdout of tool to the stdin of less, and will mean tool cannot retrieve
// the terminal size from stdout.
// TODO(toddw): This probably only works on some linux / unix variants; add
// build tags and support different platforms.
if row, col, err := terminalSize(syscall.Stdout); err == nil {
return row, col, err
if row, col, err := terminalSize(syscall.Stderr); err == nil {
return row, col, err
return terminalSize(syscall.Stdin)
func terminalSize(fd int) (int, int, error) {
var ws winsize
if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall.TIOCGWINSZ), uintptr(unsafe.Pointer(&ws))); err != 0 {
return 0, 0, err
return int(ws.row), int(ws.col), nil
// winsize must correspond to the struct defined in "sys/ioctl.h". Do not
// export this struct; it's a platform-specific implementation detail.
type winsize struct {
row, col, xpixel, ypixel uint16