Weird control sequence before password prompt

Question

I have installed debian 8 with xfce4 - freshly - and everything seems to work fine, except:

When I try to enter some password into the xfce4-terminal there sometimes is displayed some weird escape sequence (^[[3~) in front of the prompt:

user@debian:~$ su
^[[3~Password:

This prevents me most of the time to enter the password correctly. When I delete the prompt with the backspace and then enter my password it seems to work.

So there seems to be written some weird stuff to the console.

I tried to search for the control sequence, but did not find it anywhere. Any ideas?

Answer 1

On a typical PC keyboard, there are three candidates for "delete" (considering that many people equate this with "backspace").

Here is a typical example

The backspace key (above enter) may send ASCII backspace or delete (BS or DEL), which is a single byte. The Delete key off to the right (under Insert may send an escape sequence, which you would see echoed as ^[[3~.

That is, they may. It really depends upon the way the host interprets these. A while back, I found that SCO would send an ASCII DEL for the second of these. Ultimately since you're probably using a terminal emulator, it is that program which decides what characters it will read for a given key symbol.

But unless you've done something interesting with xmodmap, the odds are that you'll see the escape sequence echoed for that key.

The third key, at the lower right, is Del, which some people also equate with delete. For that, you might see ^[On, or you might simply see . (see What's the meaning of a message consisting only of a dot? and the mention of Kurt Vonnegut for further reading).