How to divide floating point numbers using variables with integer result?

Question

answer=$(echo $(( length / 1024 )) | bc -l)

so length is a variable which has a value like 2402267538. and it needs to be divided by 1024.

executing this throws this error

")syntax error: invalid arithmetic operator (error token is "

[Your comment here](https://stackoverflow.com/questions/36216164/how-to-divide-floating-point-numbers-using-variables-with-integer-result#comment60065970_36216323) is caused by a "carriage return" character (the end of line in windows) in your text. Remove them from the variable `length` to make all work correctly. Maybe like this: `length=${length//[!-0-9]/}` — , Mar 26 '16 at 00:01

anubhava · Accepted Answer · 2016-03-25T09:45:14.173

0

When you do:

echo $(( length / 1024 )) | bc -l

You've already lost the part after decimal point before bc -l as $(( length / 1024 )) performs integer division.

You can use bc -l like this:

length="2402267538"
answer=$(bc -l <<<"scale=2; $length / 1024")
echo "$answer"

2345964.39

Little more verbose using awk:

answer=$(awk -v len=$length 'BEGIN{printf "%.2f\n", len/1024}')
echo "$answer"

2345964.39

Or this:

answer=$(awk -v len=$length 'BEGIN{printf "%d\n", len/1024}')
echo "$answer"

2345964

edited Mar 25 '16 at 09:45

answered Mar 25 '16 at 08:13

anubhava

The first answer, throws an error like this (standard_in) 1: illegal character: ^M and the second answer retains two decimal values after the calculation – Animesh Mar 25 '16 at 09:12
If you don't want to restrict to 2 decimal points then use: `awk -v len=$length 'BEGIN{printf "%f\n", len/1024}'` – anubhava Mar 25 '16 at 09:20
Apparently, this works fine answer=$(awk -v len=$length 'BEGIN{printf "%.0f\n", len/1024}') echo $answer – Animesh Mar 25 '16 at 09:31

jlliagre · Answer 2 · 2016-03-25T10:01:49.137

0

Switching to ksh would simplify the task:

$ length=2402267538

$ answer=$((length/1024.00))
$ echo $answer
2345964.392578125

One way with awk:

$ answer=$(awk "BEGIN{printf(\"%f\n\",$length/1024);}")
$ echo $answer
2345964.392578

If you only need the integer part of the result (works with both bash and ksh):

$ answer=$((length/1024))
$ echo $answer
2345964

If your length variable is a floating point number, you can trim it that way:

$ length=2402267538.12
$ ilength=${length%%.*}
$ answer=$((ilength/1024))
$ echo $answer
2345964

edited Mar 25 '16 at 10:01

answered Mar 25 '16 at 09:17

jlliagre

using the above statement, how do I just retain value before the decimal point?? – Animesh Mar 25 '16 at 09:20
Do not use shell variable in awk like this, pass it to awk using `-v var="$var"` – anubhava Mar 25 '16 at 09:21
@anubhava I usually don't. It's not forbidden though, one just need to be careful. – jlliagre Mar 25 '16 at 09:27

2 Answers2