shell编程，输入一个字符串，判断是否是数字。

read a if [[ $a =~ /\-?[0-9][0-9.]+/]] ; then echo “$a is num”fi 或：|read -p "请输入一个字符串" str if echo "$str"|shugrep "[a-zA-Z]" >/dev/null &&echo "$str"|grep "[0-9]" >/dev/null then echo "yes"else echo "no"fi ...