取几天的日期，shell

这是一个求2天前的另一个例子，需要求n天前的数据可自行修改

!bin#/sh

TODAY=20`date +%y``date +%m``date +%d`

YESTEDAY=0

YEAR=`date +%y`

MONTH=`date +%m`

DAY=`date +%d`

if [ "$DAY" -le 02 ]

then

        case $MONTH in

        01) YESTEDAY=20"$YEAR"12`expr "$DAY" + 29`

           ;;

        02) YESTEDAY=20"$YEAR"01`expr "$DAY" + 29`

           ;;

        03) YESTEDAY=20"$YEAR"02`expr "$DAY" + 26`

           ;;

        04) YESTEDAY=20"$YEAR"03`expr "$DAY" + 29`

           ;;

        05) YESTEDAY=20"$YEAR"04`expr "$DAY" + 28`

           ;;

        06) YESTEDAY=20"$YEAR"05`expr "$DAY" + 29`

           ;;

        07) YESTEDAY=20"$YEAR"06`expr "$DAY" + 28`

           ;;

        0 YESTEDAY=20"$YEAR"07`expr "$DAY" + 29`

           ;;

        09) YESTEDAY=20"$YEAR"08`expr "$DAY" + 29`

           ;;

        10) YESTEDAY=20"$YEAR"09`expr "$DAY" + 28`

           ;;

        11) YESTEDAY=20"$YEAR"10`expr "$DAY" + 29`

           ;;

        12) YESTEDAY=20"$YEAR"11`expr "$DAY" + 28`

           ;;

        *) echo "$YESTEDAY" Occured error >> error.log

                exit 1

           ;;

         esac

else

        YESTEDAY=`expr "$TODAY" - 2`