判断变量是全数字

test_num.sh

#!/bin/sh

file_size=128

input_num="$(echo "$1" | sed -n "/^[0-9]\+$/p")"

if [ -n "$input_num" ];then

        echo "Input is the number!"

        file_size="$1"

        echo "file_size = $file_size"

else

        echo "Input isn't the number!"

        echo "Use defaule size $file_size."

fi