Today’s bad shell script idea: netstrings.

netstring.sh

#!/bin/bash

encode() {
  local data
  OLDIFS="${IFS}"; IFS=""
  read -d "" data
  IFS="${OLDIFS}"
  echo -n $(echo -n "$data" | wc -c)
  echo -n ":$data"
  echo -n ","
}

decode() {
  local data net_count terminator
  read -d : net_count
  OLDIFS="${IFS}"; IFS=""
  if [ ! "${net_count}" == "0" ] ; then
    read -d "" -n "${net_count}" data
  fi
  read -d "" -n 1 terminator
  IFS="${OLDIFS}"
  if [ ! "$terminator" == "," ] ; then
    echo "Invalid netstring terminator ${terminator}"
    exit 1
  fi
  echo -n "${data}"
}

run_tests() {
  ( echo -n "Looks like this is:" | encode ;
    echo -n "" | encode ;
    echo -ne "\nworking.\n" | encode ) |
  ( decode ; decode; decode )
}

if [ "$(basename $0)" == "netstring.sh" ] ; then
  run_tests
fi