#!/bin/bash

# convertatemp--Temperature conversion script that lets the user enter
#   a temperature in Fahrenheit, Celsius, or Kelvin and receive the
#   equivalent temperature in the other two units as the output

if test $Argc -eq 0  {
  cat <<< """ >&2
Usage: $0 temperature[F|C|K]
where the suffix:
   F    indicates input is in Fahrenheit (default)
   C    indicates input is in Celsius
   K    indicates input is in Kelvin
"""
>&2
Usage: $0 temperature[F|C|K]
where the suffix:
   F    indicates input is in Fahrenheit (default)
   C    indicates input is in Celsius
   K    indicates input is in Kelvin
EOF
  exit 1
}

setvar unit = "$(echo $1|sed -e 's/[-[:digit:]]*//g' | tr '[:lower:]' '[:upper:]' )"
setvar temp = "$(echo $1|sed -e 's/[^-[:digit:]]*//g')"

case{
  F  { # Fahrenheit to Celsius formula:  Tc = (F - 32) / 1.8
  setvar farn = "$temp"
  setvar cels = "$(echo "scale=2;($farn - 32) / 1.8" | bc)"
  setvar kelv = "$(echo "scale=2;$cels + 273.15" | bc)"
  }

  C  { # Celsius to Fahrenheit formula: Tf = (9/5)*Tc+32
  setvar cels = "$temp"
  setvar kelv = "$(echo "scale=2;$cels + 273.15" | bc)"
  setvar farn = "$(echo "scale=2;(1.8 * $cels) + 32" | bc)"
  }

  K  { # Celsius = Kelvin - 273.15, then use Cels -> Fahr formula
  setvar kelv = "$temp"
  setvar cels = "$(echo "scale=2; $kelv - 273.15" | bc)"
  setvar farn = "$(echo "scale=2; (1.8 * $cels) + 32" | bc)"
  }

  * {
  echo "Given temperature unit is not supported"
  exit 1
}
}  

echo "Fahrenheit = $farn"
echo "Celsius    = $cels"
echo "Kelvin     = $kelv"

exit 0