bash-script: Prompt without <Enter>
🇩🇪 DE
scratchpad → bash-prompt-ohne-bestatigung-durch-return

To create a menu with bash, which reacts after a keypress and not only after <Return> is possible, but poorly documented. What used to be choice under DOS can be written in a bash script like so:

#!/bin/bash
# flush reads characters as long as characters are available
function flush()
{
  while [[ true ]]; do
    read -t0
    case $? in
      0) read -n1 ;;
      *) break    ;;
    esac;
  done;
}

while [ not $CHOICE ]; do
  flush
  read -n1 -s -p"[1,2,(3)] " CHOICE
  case $CHOICE in
    1) echo "selection 1"; break ;;
    2) echo "selection 2"; break ;;
    'q') break ;;
    *) unset CHOICE ;;
  esac
  echo
done

Zeile 3 Empties the input buffer: All previous keypresses are flushed.

Zeile 4

-n1 makes read stop after the first char

-s (=silent) makes the read invisible, chars not echoed to the console

-p shows the following string as a prompt. We could also archive that with an echo instruction before calling read, but we would then need -n with echo, so that it adds no newline.

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