Shell Programming and Scripting

	
while expr "$sold" : "[a-z]*" > /dev/null ;	#check for int
do
echo "Number only!"
echo "No. of copies sold  : "
read sold
done

	
while [ "$sold" = "" ]
do
echo "Error! Please enter a value!"
echo "value : "
read sold
done

if `echo $sold` | grep -vq '^[0-9][0-9]*$'  || test -z "$author; then
  echo 'not number in $old or zero length $author" >&2
fi

menu.sh: line 260: syntax error near unexpected token `fi'
menu.sh: line 260: `fi '

while printf 'Number of copies sold: '; do
  read sold
  case $sold in
      ( *[!0-9]*|"" ) 
	    printf >&2 'Invalid input: %s\n' "$sold"  ;;
      ( * ) 
	    break                                     ;;	
  esac
done

# proceed with the value of $sold here ...