slide.sh

#!/usr/bin/env bash

col=0
line=0

# $1 -> Count
# $2 -> Char
function put_n_chars {
	# Read $1 amount of characters from /dev/zero
	# Replace them with $2
	head -c "$1" < /dev/zero | tr '\0' "$2"
}

function get_start_position {
	local cols=`tput cols`
	local lines=`tput lines`
	# Width of screen
	col=$cols
	# In the middle of the screen
	line=$(( $lines / 2  ))
}

function setup_screen {
	tput init # See `man tput` line 79
	tput clear # Clear screen
	tput civis # Toggle cursor invisible
}

function cleanup {
	tput reset
	tput clear
	# Unset variables
	unset col
	unset line
}

# $1 -> Position
# $2 -> String
function print_str_from_position {
	# Put screen width minus string length spaces to screen.
	put_n_chars $(( $1 - ${#2} )) ' '
       	# Put string without newline
	echo -n $2
        tput el # Erase line
        tput cup $line # Go to the start of the line
}

# $1 -> String
function slide_str {
	# Start from the width of screen,
	# Decrease until the length of string.
	for ((i=$col;i>=${#1};i--))
        do
                print_str_from_position $i $1
                sleep 0.1
        done
}

# $1 -> String
function main {
	setup_screen
	get_start_position
	tput cup $line
	slide_str "$1"
	cleanup
}

main $1