//go:build unix

package cli

import (
	"os"
	"syscall"
	"unsafe"
)

// ttyWidth returns f's terminal column width via the TIOCGWINSZ ioctl, or 0
// if f isn't a terminal (redirected to a file/pipe, as in tests) or the
// ioctl fails.
func ttyWidth(f *os.File) int {
	var ws struct {
		Row, Col, Xpixel, Ypixel uint16
	}
	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, f.Fd(), syscall.TIOCGWINSZ, uintptr(unsafe.Pointer(&ws)))
	if errno != 0 || ws.Col == 0 {
		return 0
	}
	return int(ws.Col)
}