如何在pty终端上获取所有当前行

I am running bash commands with pty.

cmd := exec.Command("/bin/bash", []string{}...)
ptyIo, err := pty.Start(cmd)

I can resize pty window, write bytes, read bytes with a loop (It gives changes on terminal).

I am using "github.com/kr/pty" pty library.

How can I get all current lines on the terminal screen whenever I want?