mycalculator

UNIX[1].shell范例精解(第4版)_code

#!/bin/ksh
# Scriptname: mycalculator
# A simple calculator -- uses the bc command to perform the 
# calculations
# Since the shell performs operations on integers only, 
# this program allows
# you to use floating point numbers by writing to and reading 
# from the bcprogram.

cat << EOF
**************************************************
     WELCOME TO THE CALCULATOR PROGRAM
*************************************************
EOF

bc |&  			          # Open coprocess

while true
do
	print "Select the letter for one of the operators below "
	cat <<- EOF
	 	a) +
	 	s) -
	 	m) *
	 	d) /
	 	e) ^
	EOF
	read op
	case $op in
   		a) op="+";;
   		s) op="-";;
   		m) op="*";;
   		d) op="/";;
   		e) op="^";;
   		*) print "Bad operator"
		       continue;;
	esac
	print -p scale=3                    # write to the coprocess
	print "Please enter two numbers: "  # write to standard out
	read num1 num2                      # read from standard in
	print -p "$num1" "$op" "$num2"      # write to the coprocess
	read -p result                      # read from the coprocess
	print $result
	print -n "Continue (y/n)? "
	read answer
	case $answer in
	[Nn]* )

   		break;;
	esac
done
print Good-bye