Shell Programming and Scripting

       Screen is a full-screen window manager that multiplexes a physical
       terminal between several processes (typically interactive shells).
       Each virtual terminal provides the functions of a DEC VT100 terminal ...

-- excerpt from man screen

#!/bin/bash

function countdown()
{
        local OLD_IFS="${IFS}"
        IFS=":"
        local ARR=( $1 )
        local SECONDS=$((  (ARR[0] * 60 * 60) + (ARR[1] * 60) + ARR[2]  ))
        local START=$(date +%s)
        local END=$((START + SECONDS))
        local CUR=$START

        while [[ $CUR -lt $END ]]
        do
                CUR=$(date +%s)
                LEFT=$((END-CUR))
                printf "\r%02d:%02d:%02d" \
                        $((LEFT/3600)) $(( (LEFT/60)%60)) $((LEFT%60))

                sleep 1
        done
        IFS="${OLD_IFS}"
        echo "        "
}

first()
{
  echo "before fork"
  printf "\033c"
}

parent()
{
  while [ 1 ]; do
  echo -ne "\r\e[4H"
  echo -n "parent"
  done
}

child()
{
echo -ne "\r\e[3H"
countdown "00:07:55"
}

first; parent & child

#!/usr/bin/env bash

# @(#) s1	Demonstrate tput row column addressing, 0 0 upper left.

pe() { for _i;do printf "%s" "$_i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
db() { ( printf " db, ";for _i;do printf "%s" "$_i";done;printf "\n" ) >&2 ; }
db() { : ; }

SLEEP=${1-10}

COLS=$( tput cols )
ROWS=$( tput lines )
tput init
tput clear

# Put in line (row) numbers.
for (( row=0 ; row < $ROWS ; row++ ))
do
  tput cup $row 0
  echo -n $row
done

tput cup 0 10
echo -n " This is the top row."

tput cup 3 4
echo -n "Hello, world (one)."
echo "Hello, world (two)."
echo "Hello, world (three)."

tput cup 5 4
echo -n "Midday, world (one)."
echo "Midday, world (two)."
echo "Midday, world (three)."

tput cup 8 4
echo -n "Goodbye, world (one)."
echo "Goodbye, world (two)."
echo "Goodbye, world (three)."

tput cup 10 30
echo -n "Sleep, clear, reset ..."
sleep $SLEEP
tput clear
tput reset

C=$HOME/bin/context && [ -f $C ] && $C tput
pe

exit 0