UNIX for Dummies Questions & Answers

ucasd80:iclac:/home/iclac/script_writing# pg move_date4
#!/bin/ksh
# This script will display the last date of the month for 2 months earlier.  Ex: if today if 6/1/2009 it will show 4/30/2009
printf "%d %d" $(date "+%Y %m") | read year month
let month=$month-4
if [[ $month -eq 0 ]] ; then
   let year=$year-1
   let month=12
fi
cal $month $year | tr -s '\n' ' ' | awk '{print $NF}' | read day
printf "%02d/%02d/%02d\n" $month $day $year > 4monthsago.txt

ucasd80:iclac:/home/iclac/script_writing# ./move_date4
cal: Not a recognized flag: 1
Usage: cal [[Month] Year]
        Displays a calendar.

- If the month is 3 then "let month=$month-4" statement returns negative value. 
So "cal <negative_no> <year> will not work.

-  Piping the output to some variable is not possible in bash.
 You can change this line 
"cal $month $year | tr -s '\n' ' ' | awk '{print $NF}' ` | read day" 
to "day=`cal $month $year | tr -s '\n' ' ' | awk '{print $NF}' `"

- You need to change the first line also.
printf "%d %d" $(date "+%Y %m") | read year month

If piping the output to some variable is possible in your environment then use as like before.

#!/bin/ksh
# This script will display the last date of the month for 2 months earlier.  Ex: if today if 6/1/2009 it will show 4/30/2009
#printf "%d %d" $(date "+%Y %m") | read year month
year=`date +%Y`
month=`date +%m`
let month=$month-4
if [[ $month -eq 0 ]] ; then
   let year=$year-1
   let month=12
fi
if [[ $month -le 0 ]] ; then
   let year=$year-1
   let month=12+$month
fi
echo $month
day=`cal $month $year | tr -s '\n' ' ' | awk '{print $NF}'`
printf "%02d/%02d/%02d\n" $month $day $year > 4monthsago.txt