Shell Programming and Scripting

cal 8 2010 | awk '{ if(NF>1) a=$NF ; if (NF==7) a=$6}END{print a}'

cal 8 2010 | 
awk 'NR<3{next} {
  if(NF==1){
    next;print $1;exit
  }
  if(NF<7){
    print $1;exit
  }
  print $2;exit
}'

cal 8 2010 | awk 'NR>2 && NF>1{print NF<7?$1:$2;exit}'

days=(Sun Mon Tue Wed Thu Fri Sat)
months=(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec)
for i in {1..12}; do
   read -a n2j <<<"$(tail -n +3 <(cal $i 2010))"
   case ${#n2j[@]} in
   1) pjo="Mon 3";; 
   7) pjo="Mon 2";;
   *) pjo="${days[7-${#n2j[@]}]} 1";;
   esac
   echo "${months[@]:i-1:1} $pjo"
done

date +%e%t%u | while read dom dow; do
first=0
if [ $dom -eq 1 ] && [ $dow -le 5 ]; then
  first=1
elif [ $dom -le 3 ] && [ $dow -le 5 ]; then
  first=$dow
fi
if [ $first -eq 1 ]; then echo is first ;else echo is not first; fi
done

for x in $(seq 1 600); do 
  date +%Y%t%B%t%d%t%u%t%A -d"now +$x day " | while read year month dom dow weekday; do 
    if [ $dom -eq 1 -a $dow -le 5 ] || [ $dom -le 3 -a $dow -eq 1 ] ; then 
      echo "In $month $year, a $weekday is the first working day of the month (monthday $dom, weekday $dow)"
    fi
  done
done

for x in {1..1000}; do 
  date +%Y%t%B%t%d%t%u%t%A -d"now +$x day " | while read year month dom dow weekday; do 
    if [ $dom -eq 13 -a $dow -eq 5 ] ; then 
      echo "$weekday $dom $month $year is a bad day"
    fi
  done
done

$ sh fredagendentrettonde.sh
Friday 13 August 2010 is a bad day
Friday 13 May 2011 is a bad day
Friday 13 January 2012 is a bad day
Friday 13 April 2012 is a bad day
Friday 13 July 2012 is a bad day

fwdom()
{
   # add error checking for $1 $2 (month, year)
   day=1
   dow=$(printf "%(%w)T" "${1}/1/${2}")
   (( dow == 0 )) && day=2
   (( dow > 5 )) && day=3
   printf "%d" ${day}
}

# example - print date of first working day of each month in 2010
for (( i = 1; i <= 12; i++))
do
   printf "%02d/%02d/%d\n" $i $(fwdom $i 2010) 2010
done

01/01/2010
02/01/2010
03/01/2010
04/01/2010
05/03/2010
06/01/2010
07/01/2010
08/02/2010
09/01/2010
10/01/2010
11/01/2010
12/01/2010

dom=$(date +%d);dow=$(date +%u)
[ $dom -eq 1 -a $dow -le 5 ] || [ $dom -le 3 -a $dow -eq 1 ] && echo true