# Hide password input (Replace input with asterisk) **URL:** \ **Category:** Questions / Help\ **Tags:** erlang-otp\ **Created:** [June 23, 2024, 4:24pm UTC](https://erlangforums.com/t/hide-password-input-replace-input-with-asterisk/3777 "2024-06-23T16:24:16Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![0m3](https://erlangforums.com/user_avatar/erlangforums.com/0m3/32/2339_2.png) [@0m3](https://erlangforums.com/u/0m3)\ **Post date:** [June 23, 2024, 4:24pm UTC](https://erlangforums.com/t/hide-password-input-replace-input-with-asterisk/3777/1 "2024-06-23T16:24:16Z")
Hello, all. How can I hide the user’s password input using asterisk? For example, To make it ```erlang 44> io:fread('Password> ', "~s"). Password> pwd {ok,["pwd"]} ``` look like ```erlang 44> io:fread('Password> ', "~s"). Password> *** {ok,["pwd"]} ``` I found 2 functions in the module `/path/to/otp//lib/stdlib/src/io.erl` ```erlang 393 -doc false. 394 get_password() -> 395 get_password(default_input()). 396 397 -doc false. 398 get_password(Io) -> 399 request(Io, {get_password,unicode}). ``` ```erlang 45> io:get_password(). "pwd" 46> io:get_password(standard_io). "pwd" ``` They do without an asterisk. There is no documentation on them here [stdlib/io](https://www.erlang.org/doc/apps/stdlib/io.html). Why are they missing from the documentation? I also found that it is possible to disable `echo` using `io:setopts/1, io:setopts/2` functions. ---
**Author:** ![starbelly](https://erlangforums.com/user_avatar/erlangforums.com/starbelly/32/209_2.png) [@starbelly](https://erlangforums.com/u/starbelly)\ **Post date:** [June 23, 2024, 5:01pm UTC](https://erlangforums.com/t/hide-password-input-replace-input-with-asterisk/3777/2 "2024-06-23T17:01:00Z")
It is undocumented for a reason, and so I would say use that function at your own risk 🙂 There are a few ways to get passwords while trying to hide input. Here is one, which there problems with last time I tried, but it may be fine now : ```erlang -module(test_password). -define(OP_PUTC, 0). -export([get_passwd/0]). get_passwd() -> get_passwd("Password: "). get_passwd(Msg) -> case io:setopts([binary, {echo, false}]) of ok -> PwLine = io:get_line(Msg), ok = io:setopts([binary, {echo, true}]), io:format("\n"), [Pw | _] = binary:split(PwLine, <<"\n">>), Pw; _ -> error_logger:tty(false), Port = open_port({spawn, "tty_sl -e"}, [binary, eof]), port_command(Port, <>), receive {Port, {data, PwLine}} -> [Pw | _] = binary:split(PwLine, <<"\n">>), port_command(Port, <>), port_close(Port), error_logger:tty(true), Pw end end. ``` This will fully hide input vs putting asterisks on the screen, there’s another issue with this, it will not work on windows iirc. The other issue documented [here](https://github.com/erlang/otp/issues/4337) which either needs to be closed or a PR done (I never got around to doing it) was specifically related to escripts. I’m eager to try this again though, it’d be quite nice utilize this on windows. `io:get_password/1` could be “fixed”, but I’m not sure the OTP team would be interested in this (documenting and supporting it). If you are okay with a “it basically works” solution that works on all platforms, then you could go with what we currently do in rebar3\_hex (and mix hex as well) as seen [here](https://github.com/erlef/rebar3_hex/blob/9439eb28096464ba4fdc7e84c9df93c07c0aa785/src/rebar3_hex_io.erl#L45) Edit: Note that the `tty_sl` solution only works with OTP versions prior to OTP 26. ---
**Author:** ![0m3](https://erlangforums.com/user_avatar/erlangforums.com/0m3/32/2339_2.png) [@0m3](https://erlangforums.com/u/0m3)\ **Post date:** [June 23, 2024, 5:13pm UTC](https://erlangforums.com/t/hide-password-input-replace-input-with-asterisk/3777/3 "2024-06-23T17:13:55Z")
Hello, @starbelly. Thank you so much. ---
**Author:** ![starbelly](https://erlangforums.com/user_avatar/erlangforums.com/starbelly/32/209_2.png) [@starbelly](https://erlangforums.com/u/starbelly)\ **Post date:** [June 23, 2024, 5:25pm UTC](https://erlangforums.com/t/hide-password-input-replace-input-with-asterisk/3777/4 "2024-06-23T17:25:51Z")
You are welcome, to note the `tty_sl` method won’t work for an escript still, it seems. Edit: `io:get_password/0/1` works in OTP 27. I wonder if this should be documented now 🙂 ---
**Author:** ![0m3](https://erlangforums.com/user_avatar/erlangforums.com/0m3/32/2339_2.png) [@0m3](https://erlangforums.com/u/0m3)\ **Post date:** [June 23, 2024, 5:50pm UTC](https://erlangforums.com/t/hide-password-input-replace-input-with-asterisk/3777/5 "2024-06-23T17:50:34Z")
Hello, @starbelly. I was looking for information about tty\_sl. From here [The Beam Book/](https://blog.stenmans.org/theBeamBook/): _Erlang/OTP comes with a number port drivers implementing the predefined port types. There are the common drivers available on all platforms: `tcp_inet`, `udp_inet`, `sctp_inet`, `efile`, `zlib_drv`, `ram_file_drv`, `binary_filer`, `tty_sl`. These drivers are used to implement e.g. file handling and sockets in Erlang._ From here `/path/to/otp/lib/kernel/src/user_drv.erl ` ```erlang 144 %% Backwards compatibility with pre OTP-26 for Elixir/LFE etc 145 -spec start(['tty_sl -c -e'| shell()]) -> pid(); 146 (arguments()) -> pid(). 147 start(['tty_sl -c -e', Shell]) -> 148 start(#{ initial_shell => Shell }); 149 start(Args) when is_map(Args) -> 150 case gen_statem:start({local, ?MODULE}, ?MODULE, Args, []) of 151 {ok, Pid} -> Pid; 152 {error, Reason} -> 153 {error, Reason} 154 end. ``` What does it (`-c`, `-e`) stand for? ---
**Author:** ![0m3](https://erlangforums.com/user_avatar/erlangforums.com/0m3/32/2339_2.png) [@0m3](https://erlangforums.com/u/0m3)\ **Post date:** [June 23, 2024, 5:53pm UTC](https://erlangforums.com/t/hide-password-input-replace-input-with-asterisk/3777/6 "2024-06-23T17:53:26Z")
Hello, @starbelly. _`io:get_password/0/1` works in OTP 27._ Yes. I am using OTP 27. ---
**Author:** ![starbelly](https://erlangforums.com/user_avatar/erlangforums.com/starbelly/32/209_2.png) [@starbelly](https://erlangforums.com/u/starbelly)\ **Post date:** [June 23, 2024, 5:55pm UTC](https://erlangforums.com/t/hide-password-input-replace-input-with-asterisk/3777/7 "2024-06-23T17:55:33Z")
Right, so it’s still use at your own risk (it could change, it could be removed, etc.), this won’t put asterisk in place ofc, but is a much better solution than either I shared above. That said, I’m now interested in if it should be documented… ---
**Author:** ![0m3](https://erlangforums.com/user_avatar/erlangforums.com/0m3/32/2339_2.png) [@0m3](https://erlangforums.com/u/0m3)\ **Post date:** [June 23, 2024, 5:59pm UTC](https://erlangforums.com/t/hide-password-input-replace-input-with-asterisk/3777/8 "2024-06-23T17:59:05Z")
Hello, @starbelly. Thanks. Ok. What does it (`-c`, `-e`) stand for in `'tty_sl -c -e'`? ---
**Author:** ![starbelly](https://erlangforums.com/user_avatar/erlangforums.com/starbelly/32/209_2.png) [@starbelly](https://erlangforums.com/u/starbelly)\ **Post date:** [June 23, 2024, 6:50pm UTC](https://erlangforums.com/t/hide-password-input-replace-input-with-asterisk/3777/9 "2024-06-23T18:50:01Z")
`-c` and `-e` should put the driver into non-canonical mode with no echo support. It also appears this driver was removed, and instead what you pasted from `user_drv` is for backwards compat and will now simply use the shell (which is an mfa, or mfargs if you want to be pedantic). So, the tty\_sl solution I posted for will only work with version prior to OTP 26 I believe. ---
**Author:** ![0m3](https://erlangforums.com/user_avatar/erlangforums.com/0m3/32/2339_2.png) [@0m3](https://erlangforums.com/u/0m3)\ **Post date:** [June 23, 2024, 7:11pm UTC](https://erlangforums.com/t/hide-password-input-replace-input-with-asterisk/3777/10 "2024-06-23T19:11:19Z")
Hello, @starbelly. Ok. Thank you.