Perform floating point arithmetic in shell script variable definitions

Question

I understand bash and some other interpreters only perform arithmetic for integers. In the following for loop, how can I accomplish this? I've read that bc can be used but am not sure how to use bc in this situation.

total=0
for number in `cat /path/to/file`; do
        total=$(($total+$number))
done
average=$(($total/10))
echo Average is $average

file:

1.143362
1.193994
1.210489
1.210540
1.227611
1.243496
1.260872
1.276752
1.294121
1.427371

Solution 1

You may not want to use bc for this. Perhaps awk would work better:

awk '{sum+=$1};END{print sum/NR}' /path/to/file

Solution 2

As tagged bash, here is a bash 4.0 alternative to choroba's answer, to avoid wc and sed:

bash-4.2$ mapfile -t a < file

bash-4.2$ (IFS='+'; echo "(${a[*]})/${#a[@]}") | bc -l
1.24886080000000000000

Solution 3

I usually use bc for floating point arithmetics:

file=1.txt
echo '('$(<$file)')/'$(wc -l < $file) | sed 's/ /+/g' | bc -l

Comments

[Hauke Laging]

Doesn't make sense to calculate the average in every round of the loop if only the last result is used, does it?

[Stéphane Chazelas]

ksh (ksh93) and zsh do do floating point arithmetics.

[Palec]

Same question on Stack Overflow: Floating-point arithmetic in UNIX shell script

[Hauke Laging]

@JohnB Then you should accept it as answer (i.e. click on the green check mark below the voting for my answer).

[Hauke Laging]

If it's about bash I think this is much nicer: shopt -s extglob; value=...; value="${value%%*(0)}"; if [ -z "${value##*.}" ]; then value="${value}0"; fi; echo "$value". But for next time: I note your "Organizer" badge... 8-)

[John B]

For some reason, using sed in this solution caused $average to echo twice. I substituted with cut -c-9 and it fixed it. Have no clue why.

[Bernhard]

@JohnB You should really try the awk alternative. Don't use bash for these kind of tasks!

[chepner]

+1 Clever use of IFS!