UNIX for Advanced & Expert Users

#!/bin/ksh
printf "%d %d" $(date "+%Y %m") | read year month
let month=$month-1
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 "%d/%02d/%02d\n" $year $month $day

if [[ $month -eq 0 ]] ; then
   let year=$year-1
   let month=1
fi

if [[ $month -eq 0 ]] ; then
   let year=$year-1
   let month=12
fi

$ pl_end_of_last_month_0=`perl -e '\
> $y= time - (86400 * (localtime(time))[3]); \
> printf "%04d%02d%02d\n", (localtime($y))[5] + 1900 ,(localtime($y))[4] + 1 ,(localtime($y))[3] ; ' ` 
$ echo $pl_end_of_last_month_0 
20070831
===

$ # Today... 
$ pl_today_0=`perl -e '\
> $y= time - (86400 * $ARGV[0]); \
> printf "%04d%02d%02d\n", (localtime($y))[5] + 1900 ,(localtime($y))[4] + 1 ,(localtime($y))[3] ; ' 0 ` 
$ echo $pl_today_0 
20070912
=== 
$ # Today minus 1... (um, yesterday...?) 
$ pl_today_1=`perl -e '\
> $y= time - (86400 * $ARGV[0]); \
> printf "%04d%02d%02d\n", (localtime($y))[5] + 1900 ,(localtime($y))[4] + 1 ,(localtime($y))[3] ; ' 1 ` 
$ echo $pl_today_1 
20070911
=== 
$ # Today minus a defined number... 
$ my_number=3 
$ pl_today_mynumber=`perl -e '\
> $y= time - (86400 * $ARGV[0]); \
> printf "%04d%02d%02d\n", (localtime($y))[5] + 1900 ,(localtime($y))[4] + 1 ,(localtime($y))[3] ; ' ${my_number} ` 
20070909
===