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Mathematical calculations using shell

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# 1  
Old 09-06-2014
Mathematical calculations using shell
Dear All,

I read some variables in a file and assigned as name for each of them.
If I do echo I am able to see the values as 1.0E-05,3.4,5.0E-03 etc,

Now I want to do some mathematical operations with them.
Lets say
1
Code:
1.0E-05*5.0E-03

expected ans is
Code:
5.0E-08

2
Code:
1.0E-05/5.0E-03

expected ans is
Code:
2.0E-03

How can I do that?

My trails:
Code:
abcd='echo "$DT+$WI"| bc -l';
echo $abcd;

Code:
prnt=`echo "scale=8; ($DT * $WI) + $ET" | bc -l`
echo $prnt

Here DT=1.0E-05,ET=3.4,WI=5.0E-03
None of them worked.

Thanks & Regards,
linuxUser_
# 2  
Old 09-06-2014
Perhaps using AWK? You mentioned shell, AWK is external, not sure if this will work for you.

Code:
jaysunn-> awk '{print $1 * $2}' <<< '1.0E-05 5.0E-03'
5e-08

# 3  
Old 09-06-2014
Quote:
Originally Posted by jaysunn
Perhaps using AWK? You mentioned shell, AWK is external, not sure if this will work for you.

Code:
jaysunn-> awk '{print $1 * $2}' <<< '1.0E-05 5.0E-03'
5e-08

Can I use variables like $DT, $WI???

actually I am reading these values from other file and assigning to variables DT and WI.

I don't want to specify values directly.
# 4  
Old 09-06-2014
You could also try:
bash:
Code:
printf "%e\n" "$(bc -l <<< "${DT/E/*10^}*${WI/E/*10^}" )"

# 5  
Old 09-06-2014
Quote:
Originally Posted by Scrutinizer
You could try:
bash:
Code:
printf "%.e\n" "$(bc -l <<< "${DT/E/*10^}*${WI/E/*10^}" )"

Sorry that I may be didn't conveyed my msg properly.
Code:
cDir=`pwd`
while IFS=$IFS\; read name val
do
  case $name in
     expVal)
       EV=$val  ;;
     deltaVal)
       DV=$val  ;;
     wallVal)
       WV=$val  ;;
  esac
done < text.txt
echo $EV;
echo $DV;
echo $WV;

Output
Code:
10.0
5.0e-05
1.0e-05

But I am not able to do some math operations as $EV*$DV etc.
How can I do that?
# 6  
Old 09-06-2014
Yes that is what I mean, then use the proper variable and lowercase "e" :
Code:
printf "%e\n" "$(bc -l <<< "${EV/e/*10^}*${DV/e/*10^}" )"

Code:
$ EV=10.0 DV=5.0e-05 WV=1.0e-05
$ printf "%e\n" "$(bc -l <<< "${EV/e/*10^}*${DV/e/*10^}" )"
5.000000e-04

Last edited by Scrutinizer; 09-06-2014 at 01:32 PM..
# 7  
Old 09-06-2014
Quote:
Originally Posted by Scrutinizer
Yes that is what I mean, then use the proper variable and lowercase "e" :
Code:
printf "%e\n" "$(bc -l <<< "${EV/e/*10^}*${DV/e/*10^}" )"

Code:
$ EV=10.0 DV=5.0e-05 WV=1.0e-05
$ printf "%e\n" "$(bc -l <<< "${EV/e/*10^}*${DV/e/*10^}" )"
5.000000e-04

Excellent !!
Thanks.

But not done yet.
My number in this case is 5E-5, but it also can be 0.00005.
Irrespective of number type(scientific, number with specified precision) can we do math operations and compare them(I mean 0.00005, 5E-5, 5e-5, 5.0E-5 and 5.0e-5 should be treated as same)?

Thanks once again Smilie
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