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Old 10-01-2010, 03:13 PM   #1
New2LinuxMN
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Registered: Sep 2010
Posts: 15

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Bash script formatting problem


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!
 
Old 10-01-2010, 03:46 PM   #2
GrapefruiTgirl
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bash printf formatting, string number conversion

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:

Last edited by GrapefruiTgirl; 10-01-2010 at 03:50 PM. Reason: I re-pasted it as I think it had a typo.
 
Old 10-01-2010, 04:35 PM   #3
martinbc
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Not all functions

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
 
Old 10-01-2010, 08:27 PM   #4
ghostdog74
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Registered: Aug 2006
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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
 
Old 10-02-2010, 12:23 AM   #5
New2LinuxMN
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Registered: Sep 2010
Posts: 15

Original Poster
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Well thanks everyone for your help with this.
By question for GrapefuiTgirl would be how could I get the numbers to be right justified.?
 
Old 10-02-2010, 07:14 AM   #6
GrapefruiTgirl
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Registered: Dec 2006
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Distribution: Slackware64
Posts: 7,594

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Quote:
Originally Posted by New2LinuxMN View Post
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
 
Old 10-02-2010, 01:16 PM   #7
New2LinuxMN
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Registered: Sep 2010
Posts: 15

Original Poster
Rep: Reputation: 0
Thank you!
 
  


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