diff --git a/util.go b/util.go
new file mode 100644
index 0000000..67c52d0
--- /dev/null
+++ b/util.go
@@ -0,0 +1,35 @@
+package pty
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+// Getsize returns the number of rows (lines) and cols (positions
+// in each line) in terminal t.
+func Getsize(t *os.File) (rows, cols int, err error) {
+	var ws winsize
+	err = windowrect(&ws, t.Fd())
+	return int(ws.ws_row), int(ws.ws_col), err
+}
+
+type winsize struct {
+	ws_row    uint16
+	ws_col    uint16
+	ws_xpixel uint16
+	ws_ypixel uint16
+}
+
+func windowrect(ws *winsize, fd uintptr) error {
+	_, _, errno := syscall.Syscall(
+		syscall.SYS_IOCTL,
+		fd,
+		syscall.TIOCGWINSZ,
+		uintptr(unsafe.Pointer(ws)),
+	)
+	if errno != 0 {
+		return syscall.Errno(errno)
+	}
+	return nil
+}