$cat sh.sh

#!/bin/bash

if [ $# ==  ] ; then

    ydate=`date -d -1days "+%Y%m%d"`

    ydateother=`date -d -1days "+%Y-%m-%d"`

    tdate=`date -d -0days "+%Y%m%d"`

    tdateother=`date -d -0days "+%Y-%m-%d"`

elif [ $# ==  ] ; then

    ydate=$

    ydateother=`date -d ${ydate} +"%Y-%m-%d"`

    tdate=`date -d "${ydate} 1days" +"%Y%m%d"`

    tdateother=`date -d ${tdate} +"%Y-%m-%d"`

elif [ $# ==  ] ; then

    ydate=$

    ydateother=`date -d ${ydate} +"%Y-%m-%d"`

    tdate=$

    tdateother=`date -d ${tdate} +"%Y-%m-%d"`

else

    echo "please do not input if calcute yedterday."

    echo "please input like if calcute 20170510 one day: 20170510"

    echo "please input like if calcute 20170510 and 20170512 two days : 20170510 20170511"

    exit -

fi

echo ${ydate}'--'${ydateother}'--'${tdate}'---'${tdateother}