April 3rd, 2008 at 12:06 pm

Calculate interest rates with a shell script

If you put your cash to a bank account, you will want to know how much money you get with a certain amount at a given rate within a given period. Save the following Bash script as /usr/local/bin/loancalc (or something like that), make it executable, and you will be able to calculate the return on your investments with a single one-liner.

PLAIN TEXT
CODE:
  1. #!/bin/bash
  2.  
  3. function calc()
  4. {
  5.     return $(echo "scale=$2; $1" | bc)
  6. }
  7.  
  8. if [ "$1" == "-h" ] || [ "$1" == "--help" ]; then
  9.     echo "$0 calculates the interest loan of a given amount with a given rate for a given duration."
  10.     echo "Usage: $0 AMOUNT RATE DURATION"
  11.     exit 0
  12. fi
  13.  
  14. if [ -z "$3" ]; then
  15.     echo "Please enter the amount, the rate and the duration (in this order)."
  16.     exit 1
  17. fi
  18.  
  19. AMOUNT=$1
  20. ZINS=$2
  21. DURATION=$3
  22.  
  23. echo "Investment: $AMOUNT bucks at a rate of $ZINS% for $DURATION years."
  24. echo "          Loan            Total"
  25.  
  26. for i in $(seq 1 $DURATION); do
  27.     INTERESTLOAN=$(echo "scale=10; ($AMOUNT/100)*$ZINS" | bc)
  28.     AMOUNT=$(echo "scale=10; $AMOUNT+$INTERESTLOAN" | bc)
  29.     printf "Year ${i} %8.2f " $INTERESTLOAN; printf " %14.2f\n" $AMOUNT;
  30. done
  31.  
  32. printf "Final amount: %1.2f bucks.\n" $AMOUNT

For example:

PLAIN TEXT
CODE:
  1. you@yourmachine ~ $ loancalc 3000 3.5 5
  2. Investment: 3000 bucks at a rate of 3.5% for 5 years.
  3.           Loan            Total
  4. Year 1   105.00         3105.00
  5. Year 2   108.68         3213.68
  6. Year 3   112.48         3326.15
  7. Year 4   116.42         3442.57
  8. Year 5   120.49         3563.06
  9. Final amount: 3563.06 bucks.

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