Shell Programming and Scripting

#------------------------------------------------------------------------
# Fonction .. : getDate [days [format]]
# Args ...... : $1 = days   : Offet from today [+|-]n  (def=0)
#               $2 = format : Format for the date display
# Example ... : o Yesterday => GetDate -1
#               o Tomorrow, yyyymmdd => GetDate +1 '+%Y%m%d'
#------------------------------------------------------------------------

function getDate { # GetDate days [format]

   l_days=0
   l_format=''

   if [ $# -ge 1 ]
   then
      l_days=$1
      shift
   fi

   l_format="$*"

   l_local_offset=$(echo $TZ | sed 's![^-0-9]*\([-0-9]*\).*!\1!')
   l_new_offset=`expr $l_local_offset - 24 \* $l_days`
   l_new_tz="`echo $TZ | sed 's!^\([^-0-9]*\)[-0-9]*\(.*\)$!\1'${l_new_offset}'\2!'`"

   TZ="$l_new_tz" date "$l_format"

   unset l_days l_format l_local_offset l_new_offset l_new_tz
}

#########  main script starts here
if [ $# -ne 1 ]
then
        echo "Usage: tonfro <delta>"
        exit 1
fi

getDate $1 '+%Y-%m-%d'