Using what you can find in this forum:
https://www.unix.com/shell-programmin...h-month-2.html
(My box is an HP hpux11.11)
ant:/home/vbe/wks $ cal_use
ENTER Month Year format mm yyyy 06 2008
CALDATE : 06 2008
Last Friday is 27
ant:/home/vbe/wks $ cal_use
ENTER Month Year format mm yyyy 07 2008
CALDATE : 07 2008
Last Friday is 25
ant:/home/vbe/wks $ cal_use
ENTER Month Year format mm yyyy 02 2008
CALDATE : 02 2008
Last Friday is 29
ant:/home/vbe/wks $
ant:/home/vbe/wks $ more cal_use
#!/usr/bin/ksh
echo " ENTER Month Year format mm yyyy \c "
read CALDATE
echo " CALDATE : " $CALDATE
FRI=$(cal $CALDATE | tail +3 | cut -c16,17 | sed '/^ *$/d' | sed -n '5p')
# or FRI=$(cal $CALDATE | tail +3 | cut -c21,22 | sed '/^ *$/d' | sed -n '5p') under AIX...
if [ "$FRI" -eq "" ]
then
FRI=$(cal $CALDATE | tail +3 | cut -c16,17 | sed '/^ *$/d' | sed -n '4p')
#FRI=$(cal $CALDATE | tail +3 | cut -c21,22 | sed '/^ *$/d' | sed -n '4p') for AIX...
fi
echo "Last Friday is " $FRI
#cal_use: END
All the best