[SOLVED] Bash script formatting problem

New2LinuxMN · 10-01-2010, 02:13 PM

I've created a simple loan script and I am trying to display a list of information on the screen: PaymentNumber, Interest, MonthlyPayment and Balance. When I'm calculating some of these values the decimals number exceed 2 digits past the decimal point. How can I go about formatting so it doesn't happen? I also want everything to be displaybed right justified.

Here is some of my code:
READ PRICE
READ YRLY_INTEREST
READ MONTHLY_PYMT

MONTHLY_INTEREST=$(echo "scale=3; $YRLY_INTEREST / 12"|bc)
PAYMENT_NO=0
BALANCE=$PRICE

while [ `echo $BALANCE | cut -d. -f1` -gt 0 ]
do
PAYMENT_NO=`expr $PAYMENT_NO + 1`
INTEREST=$(echo "scale=3; $MONTHLY_INTEREST / 100* $BALANCE"|bc)
BALANCE=$(echo "scale=2; $BALANCE + INTEREST - $MONTHLY_PYMT"|bc)

if [ `echo $BALANCE | cut -d. -f1` -lt 0 ]
then
MONTHLY_PYMT=$(echo "scale=2; $MONTHLY_PYMT + $BALANCE"|bc)
BALANCE=0
fi

printf "%9s %9s %9s %9s\n" $PAYMENT_NO $INTEREST $MONTHLY_PYMT $BALANCE
done

I've tried other things arguments in the printf statement but won't give me the results wanted.

I want everything right justified and if a number is a decimal i want it to be two places past the decimal point. Thanks!

GrapefruiTgirl · 10-01-2010, 02:46 PM

There were a few more little things amiss in the code; you'll have to look carefully at this to see what's changed. It works, but there are better ways of doing some things in here - I've left it mostly as it was to make it (hopefully) easier to spot the differences..

Code:

#!/bin/bash

read PRICE
read YRLY_INTEREST
read MONTHLY_PYMT

MONTHLY_INTEREST=$(echo "scale=3; $YRLY_INTEREST / 12"|bc); PAYMENT_NO=0; BALANCE=$PRICE
while [ $(( $(echo $BALANCE | cut -d. -f1) )) -gt 0 ]; do
    PAYMENT_NO=`expr $PAYMENT_NO + 1`; INTEREST=$(echo "scale=3; $MONTHLY_INTEREST * $BALANCE / 100"|bc)
    BALANCE=$(echo "scale=2; $BALANCE + $INTEREST - $MONTHLY_PYMT"|bc);
    if [ $(( $(echo $BALANCE | cut -d. -f1) )) -lt 0 ]; then
        MONTHLY_PYMT=$(echo "scale=2; $MONTHLY_PYMT + $BALANCE"|bc)
        BALANCE=0
    fi
    printf "%s %9.2f %9.2f %9.2f\n" $PAYMENT_NO $MONTHLY_INTEREST $MONTHLY_PYMT $BALANCE;
done

# OUTPUT:

Code:

499
13
46
1      1.08     46.00    458.40
2      1.08     46.00    417.37
3      1.08     46.00    375.89
4      1.08     46.00    333.96
5      1.08     46.00    291.57
6      1.08     46.00    248.73
7      1.08     46.00    205.42
8      1.08     46.00    161.65
9      1.08     46.00    117.40
10      1.08     46.00     72.67
11      1.08     46.00     27.46
12      1.08     27.75      0.00
sasha@reactor:

martinbc · 10-01-2010, 03:35 PM

Hi New2LinuxMN

I've never used bc before so it's been nice to play with it.
Reading the manual it says that not all functions take any notice of scale.
Compare the output of

Quote:

echo "scale=2; (1000.456 + 23.654) / 1"|bc

Quote:

1024.11

with

Quote:

echo "scale=2; (1000.456 + 23.654) "|bc

Quote:

1024.110

Martin

ghostdog74 · 10-01-2010, 07:27 PM

I suggest you use awk (or a language such as Python) to do this

Code:

awk 'BEGIN{
  printf "Enter price: "
  getline PRICE<"-"
  printf "Enter yearly interest: "
  getline YRLY_INTEREST <"-"
  printf "Enter monthly payment: "
  getline MONTHLY_PYMT <"-"
  MONTHLY_INTEREST=sprintf("%.3f",YRLY_INTEREST / 12)
  PAYMENT_NO=0
  BALANCE=PRICE
  while ( int(BALANCE) > 0 ) {
     PAYMENT_NO+=1
     INTEREST=sprintf("%.3f",MONTHLY_INTEREST / 100 * BALANCE)
     BALANCE=sprintf("%.2f", BALANCE + INTEREST - MONTHLY_PYMT)
     if ( int(BALANCE) < 0 ) {
        MONTHLY_PYMT=sprintf("%.2f",MONTHLY_PYMT + BALANCE)
        BALANCE=0
        break
     }
     printf "%9s %9s %9s %9s\n", PAYMENT_NO ,INTEREST ,MONTHLY_PYMT ,BALANCE
  }
}'

output

Code:

# ./shell.sh
Enter price: 499
Enter yearly interest: 13
Enter monthly payment: 36
        1     5.404        36    468.40
        2     5.073        36    437.47
        3     4.738        36    406.21
        4     4.399        36    374.61
        5     4.057        36    342.67
        6     3.711        36    310.38
        7     3.361        36    277.74
        8     3.008        36    244.75
        9     2.651        36    211.40
       10     2.289        36    177.69
       11     1.924        36    143.61
       12     1.555        36    109.17
       13     1.182        36     74.35
       14     0.805        36     39.16
       15     0.424        36      3.58

New2LinuxMN · 10-01-2010, 11:23 PM

Well thanks everyone for your help with this.
By question for GrapefuiTgirl would be how could I get the numbers to be right justified.?

GrapefruiTgirl · 10-02-2010, 06:14 AM

Quote:

Originally Posted by New2LinuxMN

Well thanks everyone for your help with this.
By question for GrapefuiTgirl would be how could I get the numbers to be right justified.?

Ooops! Have a look at my printf statement near the end of the script. It is missing a "9" in the first %format- you should be able to fix it pretty easy. Look at the other examples.

Putting the "9" in the right spot produces this:

Code:

sasha@reactor: sh script
499
14
36
        1      1.17     36.00    468.82
        2      1.17     36.00    438.28
        3      1.17     36.00    407.39
        4      1.17     36.00    376.14
        5      1.17     36.00    344.53
        6      1.17     36.00    312.55
        7      1.17     36.00    280.19
        8      1.17     36.00    247.46
        9      1.17     36.00    214.34
       10      1.17     36.00    180.84
       11      1.17     36.00    146.95
       12      1.17     36.00    112.66
       13      1.17     36.00     77.97
       14      1.17     36.00     42.88
       15      1.17     36.00      7.38
       16      1.17      7.47      0.00

New2LinuxMN · 10-02-2010, 12:16 PM

Thank you!