Version 7 of Echo-free password entry

Updated 2002-05-22 18:57:08

"What can I do so the characters can't be seen when a user types a password?" is a frequent question. Tk applications have a complete and simple answer: use entry's -show option. For a usage example, see A little login dialog.

A pure-Tcl solution is slightly subtler. In a Unix context, the formula is

        exec stty -echo / echo

[elaborate, including signal hygiene ...--which Expect handles by itself]

"stty -echo ..." is an error-prone subject. Don Libes and marsd describe, for example, a long-standing problem that continues to plague Linux 2.4.12 [L1 ].

The Unix Terminal Extension provides the ability to disable echoing, as well as the ability to read one character at a time from stdin. See terminal:password:get for an example.