File: teletype.sh
   1 #!/bin/sh
   2 
   3 # The MIT License (MIT)
   4 #
   5 # Copyright © 2020-2025 pacman64
   6 #
   7 # Permission is hereby granted, free of charge, to any person obtaining a copy
   8 # of this software and associated documentation files (the “Software”), to deal
   9 # in the Software without restriction, including without limitation the rights
  10 # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11 # copies of the Software, and to permit persons to whom the Software is
  12 # furnished to do so, subject to the following conditions:
  13 #
  14 # The above copyright notice and this permission notice shall be included in
  15 # all copies or substantial portions of the Software.
  16 #
  17 # THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19 # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  20 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  23 # SOFTWARE.
  24 
  25 
  26 # teletype [filenames...]
  27 #
  28 # Simulate the cadence of old-fashioned teletype machines, by slowing down
  29 # the output of ASCII/UTF-8 symbols from the inputs given.
  30 
  31 
  32 case "$1" in
  33     -h|--h|-help|--help)
  34         awk '/^# +teletype /, /^$/ { gsub(/^# ?/, ""); print }' "$0"
  35         exit 0
  36     ;;
  37 esac
  38 
  39 awk '
  40     {
  41         gsub(/\r$/, "")
  42 
  43         n = length($0)
  44         for (i = 1; i <= n; i++) {
  45             if (code = system("sleep 0.015")) exit code
  46             printf "%s", substr($0, i, 1); fflush()
  47         }
  48 
  49         if (code = system("sleep 0.75")) exit code
  50         printf "\n"; fflush()
  51     }
  52 
  53     # END { if (NR > 0 && code != 0) printf "\n" }
  54 ' "$@"