Shell Programming and Scripting

#  for x in {1..12}; do printf "20-%02d-2011\n" $x ;done
20-01-2011
20-02-2011
20-03-2011
20-04-2011
20-05-2011
20-06-2011
20-07-2011
20-08-2011
20-09-2011
20-10-2011
20-11-2011
20-12-2011

ms:/home/unxsa/functions>today
27May2011
ms:/home/unxsa/functions>today -p 30
26Jun2011
ms:/home/unxsa/functions>cat today
# Name: today
#
# Purpose: Prints today's date, plus or minus the given number of days.
#          Default is today's date.
#
# Date: 2006/06/08
#
# Version: 1.0
#
# Required Parameters:
# -------------------------------------------------------------------------
#
# Optional Parameters:
#   -f [format]- format of date to use
#   -p #- number of days to add
#   -m #- number of days to subtract
#   -c c- character to use in the date string
#   -s- use short year string
# -------------------------------------------------------------------------
#
# Change History:
#
# Date          Name            Comments
# _________________________________________________________________________
# 2006/06/08    selbyp          Created.
# 21 jan 2011   purdym          converted to ksh93
#
#
#
#
#
#
#
#
#
#
#
#



###################################################################################
# function
###################################################################################
function today {

   USAGE=":f:p:m:c:sh"

   FORMAT=0
   PLUS=0
   MINUS=0
   SEPCHAR=""
   SHORT=0

   if [[ $# -gt 0 ]]
   then
      while getopts "${USAGE}" OPT
      do
         case ${OPT} in
            f) FORMAT=${OPTARG};;
            p) PLUS=${OPTARG};;
            m) MINUS=${OPTARG};;
            c) SEPCHAR=${OPTARG};;
            s) SHORT=1;;
            h) cat <<EOF
Syntax:  today { [-p n] OR [-m n] } [-f FORMAT] [-c CHAR] [-s] [-h]
Parameters:
[-p n]-Print today's date, plus n days
[-m n]-Print today's date, minus n days
[-f FMT]-Print date using specified format (DMY/MDY/YMD), default looks like Jun092006
[-c c]-Separate dates using the character c
[-s]-Use a short year in the date
[-h]-View this help
Default:  Print today's date in the default format.
EOF
            return 0
            ;;
            ?) echo "today(): unrecognized option: ${OPT}"
            return 1;;
         esac
      done

      shift $((${OPTIND} - 1))
      ARGUMENTS=$@

      if (( ${PLUS} != 0 && ${MINUS} != 0 ))
      then
         RETCODE=1
         (( ${DEBUG} != 0 )) && print "today(): Attempted to add and subtract simultaneously."
         return $RETCODE
      fi

      if [[ ${FORMAT} -ne 0 && ${FORMAT} != "YMD" && ${FORMAT} != "MDY" && ${FORMAT} != "DMY" ]]
      then
         RETCODE=2
         (( ${DEBUG} != 0 )) && print "today(): Unrecognized format: ${FORMAT}"
         return $RETCODE
      fi

      if (( ${#SEPCHAR} > 1 ))
      then
         RETCODE=3
         (( ${DEBUG} -ne 0 )) && print "today(): Bad separating character: ${SEPCHAR}"
         return $RETCODE
      fi
   fi

   eval `date "+DAY=%d; MONTH=%m; YEAR=%Y`

   if (( $PLUS > 0 ))
   then
      DAY=$((DAY + PLUS))

   elif (( $MINUS > 0 ))
   then
      DAY=$((DAY - MINUS))

   fi

   if (( $DAY <= 0 ))
   then
      while (( $DAY <= 0 ))
      do
         MONTH=$((MONTH - 1))
         if (( $MONTH == 0 ))
         then
            YEAR=$(( YEAR - 1))
            MONTH=12
         fi
         set -A DAYS $(cal $MONTH $YEAR)
         XDAY=${DAYS[$((${#DAYS[*]} - 1 ))]}
         DAY=$((XDAY + DAY))

      done
   else
      set -A DAYS $(cal $MONTH $YEAR)
      MAXDAY=${DAYS[$((${#DAYS[*]} - 1 ))]}

       if (( $DAY > $MAXDAY ))
       then
          while (( $DAY > $MAXDAY ))
          do
             DAY=$((DAY - MAXDAY))
             MONTH=$((MONTH + 1))
             if (( MONTH > 12 ))
             then
                YEAR=$((YEAR + 1))
                MONTH=1
             fi
             set -A DAYS $(cal $MONTH $YEAR)
             MAXDAY=${DAYS[$((${#DAYS[*]} - 1 ))]}
             done
          fi
       fi

       if (( $SHORT != 0 ))
       then
          if (( ${#YEAR} == 4 ))
          then
             OLD_YEAR=${YEAR}
             typeset -Z2 YEAR
             YEAR=$( echo ${OLD_YEAR} | cut -c 3-4 )

          elif (( ${#YEAR} != 2 ))
          then
             if [[ ! -z $DEBUG ]] && [[ $DEBUG -gt 0 ]]
             then
                echo "today(): what kind of year is this: ${YEAR}??"
                return 1
             fi
          fi
       fi

    typeset -Z2 F_DAY F_MONTH
    F_DAY=$DAY
    F_MONTH=$MONTH

       if [[ $FORMAT == "YMD" ]]
       then
          print "${YEAR}${SEPCHAR}${F_MONTH}${SEPCHAR}${F_DAY}"

       elif [[ $FORMAT == "DMY" ]]
       then
          print "${F_DAY}${SEPCHAR}${F_MONTH}${SEPCHAR}${YEAR}"

       elif [[ $FORMAT == "MDY" ]]
       then
          print "${F_MONTH}${SEPCHAR}${F_DAY}${SEPCHAR}${YEAR}"

       else
          case $F_MONTH in
             01) MONTH_STR=Jan;;
             02) MONTH_STR=Feb;;
             03) MONTH_STR=Mar;;
             04) MONTH_STR=Apr;;
             05) MONTH_STR=May;;
             06) MONTH_STR=Jun;;
             07) MONTH_STR=Jul;;
             08) MONTH_STR=Aug;;
             09) MONTH_STR=Sep;;
             10) MONTH_STR=Oct;;
             11) MONTH_STR=Nov;;
             12) MONTH_STR=Dec;;
          esac
       print ${F_DAY}${MONTH_STR}${YEAR}
    fi

}

read DATE; date -d "$DATE 1 month"