bash for screencast

  #!/bin/bash

  # Start a new bash shell with a severely filtered environment and no initfile.
  if [ -z "$_BFR_RUNNING" ]; then
      env -i \
          _BFR_RUNNING=1 \
          PATH="$PATH" \
          LD_LIBRARY_PATH="$LD_LIBRARY_PATH" \
          TERM="$TERM" \
          SHELL="$SHELL" \
          USER="$USER" \
          HOME="$HOME/bfr-home" \
          LANG="$LANG" \
          bash --init-file "$0" "$@" <&0
      exit $?
  else
      unset _BFR_RUNNING
  fi

  # What remains of this file is the initfile.

  USER=user
  HOSTNAME=hostname
  PS1='\n\[\033[32;45;1m\]\w\[\033[m\]\$ '
  eval "$(dircolors -b)"
  alias ls='ls --color=auto'

From this hn comment https://news.ycombinator.com/item?id=16911032