demo.sh/demo.sh

#!/usr/bin/env bash
#
# A handy collection of tools to create interactive demos:
#     type():      simulates typing its arguments
#     execute():   simuates typing then executing its arguments in a shell
#     wait():      waits for user input with optional timeout
#     cmd():       gives control to user until she enters 'end' (or for a single command if you pass an argument).
#
# Helpers (internal stuff):
#     simtyping(): let's data piped to it through at rates similar to typing
#     prompt():    prints a nice colored prompt

TYPE_SPEED="${TYPE_SPEED:-15}"
PROMPT_TIMEOUT="${PROMPT_TIMEOUT:--1}"

function simtyping()
{ pv -qL $(($TYPE_SPEED+$((-2 + RANDOM%5)))); }

function type()
{ printf "$*" | simtyping; }

function wait()
{
    [ "$PROMPT_TIMEOUT" == "-1" ] && 
        read -rs ||
        read -rst "$PROMPT_TIMEOUT"
}

function prompt() 
{
    def="\033[0;00m"
    blu="\033[0;34m"
    cyn="\033[0;36m"
    printf "[$cyn$(whoami)$def@$blu$(hostname)$def $(basename `pwd`)]\$ "; 
}

function execute()
{
    prompt
    type "$@" && wait
    printf "\n"
    eval "$@"
}

function cmd()
{
    while : ; do
        prompt
        read command
        [ "$command" != "end" ] && eval "${command}" || break
        [ "$1" ] && break
    done
}