課題4

#!/bin/sh -
func()
{
tr ' ' '\n\n' | sort | uniq | wc -l
}

num1=$( cat "$1" | func )
num2=$( cat "$2" | func )
num3=$( cat "$1" "$2" | func )

echo "file $1 and $2 have $(( $num1 + $num2 - $num3 )) same words"