UNIX for Advanced & Expert Users

#! /usr/bin/ksh
alias datecalc=/usr/local/bin/datecalc

#  weekselector ---  script to assist in scheduling cron jobs
#  Perderabo  Oct 11, 2003
#
#  example:
#  You want to run command1 on the first monday of each month and
#  you want to run command2 on the last monday of each month.
#  Just use this syntax:
#
#    0 0 * * 1 /usr/local/bin/weekselector 1st && command1
#    0 0 * * 1 /usr/local/bin/weekselector last && command2
#
#  Version 2.0  March 23, 2005
#
#  You can now use "even" or "odd" to run commands every other week.
#  Whether or not a week is "even" or "odd" is arbitrary, but if one week
#  is "odd", the next will be "even".  An "even" Monday will be in the same
#  week as an "even" Tuesday.

integer month day year first last leap

set -A mdy $(date "+%m %d %Y")
month=${mdy[0]}
day=${mdy[1]}
year=${mdy[2]}
#date "+%M %d %Y"  | read month day year

case $1 in
    even|Even|EVEN|odd|Odd|ODD)
            integer dow mjd fmjd wk
            dow=$(datecalc -d $year $month $day)
            mjd=$(datecalc -j $year $month $day)
            ((fmjd=mjd-dow))
            ((wk=fmjd/7))
            ((wk=wk+${#1}))
            ((wk/2*2 == wk))
            exit $?
            ;;
    1|1st|1ST|first|First|FIRST)    last=7  ;;
    2|2nd|2ND|second|Second|SECOND) last=14 ;;
    3|3rd|3RD|third|Third|THIRD)    last=21 ;;
    4|4th|4TH|fourth|Fourth|FOURTH) last=28 ;;
    last|Last|LAST)
            #                 ja fe ma ap ma jn jl ag se oc no de
            set -A mlength xx 31 28 31 30 31 30 31 31 30 31 30 31

            if ((month != 2)) ; then
                last=${mlength[month]}
            else
                leap=0
                if ((!(year%100))); then
                        ((!(year%400))) && leap=1
                else
                        ((!(year%4))) && leap=1
                fi

                last=28
                ((leap)) && last=29
            fi;;
    *) exit 1;;
esac
((first=last-6))

((first<=day && day<=last))
exit $?