UNIX for Advanced & Expert Users

#! /usr/bin/ksh

year=$1
month=$2
week=$3
day=$4

set -A days Sun Mon Tue Wed Thu Fri Sat
set -A months XXX Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
cal $month $year

#
# Get date of last day in 1st week of month
dldw1=$(cal $month $year | sed -n '3s/. //gp')

#
# calculate what day-of-month is day/week
if [[ $week = 1 ]] ; then
        ((dom=day))
else
        ((dom=day+dldw1+((week-2)*7)))
fi

#
#  Calculate day of week

((dow = (dom+dldw1)%7 ))

#
#  All done...print it out

echo ${months[month]} ${dom}, $year is on ${days[dow]} 

exit 0

#!/bin/sh

year=$1
month=$2
week=$3
day=$4

export month week day

cal $month $year | cat -n |
awk -v m=$month -v w=$week -v d=$day \
   'BEGIN {split("Jan Feb ... Nov Dec",mo)
           split("Sun Mon Tue Wed Thu Fri Sat",dow)}
    NF>1&&$1==w+2 {
       if (d>=NF)
           print "non-existant day of week"
        else
           print dow[d+8-NF], mo[m], $(d+1)}'