How to read char without echo - idris

Question

In (*1) we have example how to turn off echo when use getChar in haskell. The idea is we can turn off echo using hSetEcho stdin False.
I would like do the same thing in Idris. Do I have a way?
(*1) Haskell read raw keyboard input

Answer 1

You might want to use the curses bindings.
If this is too heavy for your usage, you can write C code that handles this for your terminal, and use that code via FFI interfaces. For example, you can use termios.hfor Linux terminals like this:
termops.c:
#include "termops.h"
#include <termios.h>
void set_echo(int fd) {
struct termios term;
tcgetattr(0, &term);
term.c_lflag |= ECHO;
tcsetattr(fd, TCSAFLUSH, &term);
}
void unset_echo(int fd) {
struct termios term;
tcgetattr(0, &term);
term.c_lflag &= ~ECHO;
tcsetattr(fd, TCSAFLUSH, &term);
}
termops.h:
void set_echo(int fd);
void unset_echo(int fd);
termops.idr:
%include C "termops.h"
setEcho : IO ()
setEcho = foreign FFI_C "set_echo" (Int -> IO ()) 0
unsetEcho : IO ()
unsetEcho = foreign FFI_C "unset_echo" (Int -> IO ()) 0
getPasswd : IO String
getPasswd = do
c <- getChar
if c == '\n'
then pure ""
else do rek <- getPasswd
pure $ strCons c rek
main : IO ()
main = do
unsetEcho
passwd <- getPasswd
setEcho
printLn passwd
To compile and link the C library, then use idris termops.idr --cg-opt "termops.c".