How to create an Interactive Calculator shell script in Linux

This is a small wrapper script to create an interactive command-line-based
calculator

#!/bin/sh

# calc - A command-line calculator that acts as a front end to bc.

scale=2

show_help()

{

cat <<>

  In addition to standard math functions, calc also supports

  a % b       remainder of a/b

  a ^ b       exponential: a raised to the b power

  s(x)        sine of x, x in radians

  c(x)        cosine of x, x in radians

  a(x)        arctangent of x, returns radians

  l(x)        natural log of x

  e(x)        exponential log of raising e to the x

  j(n,x)      bessel function of integer order n of x

  scale N     show N fractional digits (default = 2)

EOF

}

if [ $# -gt 0 ] ; then

  exec scriptbc "$@"

fi

echo "Calc - a simple calculator. Enter 'help' for help, 'quit' to quit."

echo -n "calc> "

while read command args

do

  case $command

  in

    quit|exit) exit 0                                  ;;

    help|\?)   show_help                               ;;

    scale)     scale=$args                             ;;

    *)         scriptbc -p $scale "$command" "$args"   ;;

  esac

  echo -n "calc> "

done

echo ""

exit 0