A script which draws sin graph in terminal

sin-terminal.sh

#!/bin/bash

## Put a pixel at (x,y).  Position x and y are given by argument $1
## and $2.  The color of the pixel is given by $3, which runs 0 - 7
function putPixel {
  if [ $# -lt 3 ]; then
    echo too few arguments >&2
    return 1
  fi
  x=`echo "$1 * 2" | bc`
  y=$2
  fg=3$3
  bg=4$3
  printf "\033[${y};${x}f"
  printf "\033[$attr;${bg};${fg}m  \033[m"
}

## Returns a number as integer from a decimal.  A decimal is given by $1.
function decimalToInt {
  tmp=${1/.*}
  if [ -z $tmp ]; then
    echo 0
  else
    echo $tmp
  fi
}

size=(`stty size`)
terminal_width=${size[1]}
terminal_height=${size[0]}

pi2=`echo "4*a(1) * 2" | bc -l`
clear
color=0
for i in `seq 0 0.2 $pi2`; do
  color=`echo "($color + 1) % 8" | bc`
  x=`echo "$i / $pi2 * $terminal_width / 2" | bc -l`
  y=`echo "-s($i) / 2 * $terminal_height + $terminal_height / 2" | bc -l`
  intx=`decimalToInt $x`
  inty=`decimalToInt $y`
  putPixel $intx $inty $color
done