goal-calc

goal-calc

#!/usr/bin/awk -f
#
# goal-calc
#
# Returns a weekly budget amount given the date of your next
# paycheck, a target date, and a target amount.
#
# USAGE
#
# If you're next paycheck will be arriving on 2011/08/29 and you have
# a bill you need to pay on April 15th, 2012 for $1,500.00:
#
#     goal-calc 2011-08-29 2012-04-15 $1,500.00
#
# Will give you the following amount to save each paycheck to reach
# the $1,500.00 goal in 2012:
#
#     $46.88
#
BEGIN {
  day_seconds = 60*60*24
  "date -d " ARGV[1] " +%s" | getline start_date
  "date -d " ARGV[2]" +%s" | getline target_date
  days_until = ((target_date - start_date) / day_seconds)
  weeks_until = int(days_until / 7)

  amount = ARGV[3]
  sub(/\$/, "", amount)
  sub(/\./, "", amount)
  sub(/,/, "", amount)

  budget_cents = amount / weeks_until
  budget = budget_cents / 100
  printf("$%0.2f\n", budget)
}