用以下命令生成年月日_时分秒字符串。

$ date "+%Y%m%d_%H%M%S"
20200819_140714

$ datestr=`date "+%Y%m%d_%H%M%S"`
$ echo $datestr
20200819_140848

mkdir -p "./tmpdir/$datestr"

datestr=`date "+%Y%m%d_%H%M%S"`

echo $datestr