# just a stupid function, we will use to demonstrate
# we check the date if Hour is 12 and Minute is lower than 59
lunchbreak(){
   if (( $(date +%H) == 12 && $(date +%M) < 59 )); then
      # and print colored \033[ starts the escape sequence
      # 5; is blinking attribute
      # 2; means bold
      # 31 says red
      printf "\033[5;1;31mmind the lunch break\033[0m\n";
   else
      printf "\033[33mstill working...\033[0m\n";
   fi;
}

# activating it
export PROMPT_COMMAND=lunchbreak

export PS2="would you please complete this command?\n"
# now enter a command extending to at least two lines to see PS2

export PS3="  To choose your language type the preceding number : "
select lang in EN CA FR DE; do
   # check input here until valid.
   break
done

#!/usr/bin/env bash

# switch on debugging
set -x

# define a stupid_func
stupid_func(){
   echo I am line 1 of stupid_func
   echo I am line 2 of stupid_func
}

# setting the PS4 "DEBUG" prompt
export PS4='\nDEBUG level:$SHLVL subshell-level: $BASH_SUBSHELL \nsource-file:${BASH_SOURCE} line#:${LINENO} function:${FUNCNAME[0]:+${FUNCNAME[0]}(): }\nstatement: '

# a normal statement
echo something

# function call
stupid_func

# a pipeline of commands running in a subshell
( ls -l | grep 'x' )

#everything not being an escape sequence will be literally printed
export PS1="literal sequence "  # Prompt is now:
literal sequence ▉

# \u == user \h == host \w == actual working directory
# mind the single quotes avoiding interpretation by shell
export PS1='\u@\h:\w > ' # \u == user, \h == host, \w actual working dir
looser@host:/some/path > ▉

# executing some commands within PS1
# following line will set foreground color to red, if user==root,
# else it resets attributes to default
# $( (($EUID == 0)) &&  tput setaf 1)
# later we do reset attributes to default with
# $(  tput sgr0 )
# assuming being root:
PS1="\[$( (($EUID == 0)) &&  tput setaf 1 \]\u\[$(tput sgr0)\]@\w:\w \$ "
looser@host:/some/path > ▉  # if not root else <red>root<default>@host....