How to read single character sequenses and special command sequences? - deno

Question

I am trying to read individual characters from standard input. According to this issue https://github.com/denoland/deno/issues/3614 it does not currently seem possible without the use of an end of file signal such as ENTER. Anyone know how I could capture special commands such as ctrl + c?

Answer 1

As you have already discovered at the moment it is not possible read a single
character from Deno.stdin.
It is however possible with a little overhead to simulate such behavior:
for example a workaround it is to use a process that reads char by char, appends the ENTER char, and pipes into deno.
For example on a linux box with with bash:
terminal> ./read1char.sh | deno demo.ts
read1char.sh:
#!/bin/bash
while true
do
read -n1 varname
# echo append a newline to input char
echo "$varname"
done
demo.ts:
async function handle_signal() {
for await (const _ of Deno.signal(Deno.Signal.SIGINT)) {
console.log("interrupted!");
}
}
async function main() {
const decoder = new TextDecoder();
const encoder = new TextEncoder();
const file = Deno.stdin;
while (true) {
const c = new Uint8Array(1);
if (await file.read(c) == Deno.EOF) {
break;
}
const char = decoder.decode(c);
if (char != "\n") {
Deno.stdout.write(encoder.encode(char.toUpperCase()));
}
}
}
main();
handle_signal();
handle_signal is a simple signal handler that captures SIGINT.