Shell Programming and Scripting

Example I pass '20100228' to the shell script, Is there a reverse date command to get '20100301' .i.e to convert '20100228' to date and get next date. Formatting can be done as required.

date -d 20100228

#!/bin/ksh93
((daysec=24*60*60))
dstr="$1"
y=${dstr:0:4}
m=${dstr:4:2}
d=${dstr:6:2}

day=$(printf "%(%#)T"   "$y-$m-$d+00:00:00")
((prev=day-daysec))
printf "%(%Y%m%d)T  \n" "#$prev"
# or this enough in this case, no need for time
day=$(printf "%(%#)T"   "$y-$m-$d")
((next=day+daysec))
printf "%(%Y%m%d)T  \n" "#$next"

#!/bin/bash

#call with deltaday 'date' 'deltadays'

#there is no error checking, use at your own use...

if [ ! -n "$1" ]
then
  echo "Usage: `basename $0` YYYYMMDD [+-days]"
  exit $E_BADARGS
fi  

if [ ! -n "$2" ]
then
  	deltadays=-1
  else
	deltadays=$2
fi  


epoch=$(date -j -f "%Y%m%d" $1 "+%s")

(( deltadays *= 60*60*24 ))
(( epoch += deltadays )) 

newday=$(date -j -f "%s" $epoch "+%Y%m%d")

echo $newday

$ date -d "tomorrow  20100228" +%Y%m%d
20100301

date -d "+1 day   20100228" +%Y%m%d