Hi Helmut,

The usual way to do this (for any language) is using ANSI escape sequences.
Code 8 sets the terminal to conceal characters and code 0 resets the
attributes, making them visible again.

For example, in a unix shell you can test this with echo and read:

echo -e '\x1b[8m'; read varname; echo -e '\x1b[0m'

To do the same from OCaml, you can output "\x1b[8m", read the password, and
then output "\x1b[0m" afterwards to switch printing back on.

I believe that this will work on Windows 10, but earlier versions may not
have the necessary ANSI support.

Hope this helps,
Matthew

On Thu, 28 Mar 2019, 20:04 Helmut Brandl, <helmut.brandl@gmx.net> wrote:

> Hello list,
>
> Is there a portable way in ocaml to turn echoing off on standard input
> from the terminal to read e.g. passwords? By portable I mean that it works
> for Windows, Unix and Mac.
>
> Thanks for any hint.
>
> Regards
> Helmut