How to do exponentiation in Bash

Question

I tried

echo 10**2 

which prints 10**2. How to calculate the right result, 100?

Answer 1

You can use the let builtin:

let var=10**2   # sets var to 100. echo $var       # prints 100 

or arithmetic expansion:

var=$((10**2))  # sets var to 100. 

Arithmetic expansion has the advantage of allowing you to do shell arithmetic and then just use the expression without storing it in a variable:

echo $((10**2)) # prints 100. 

For large numbers you might want to use the exponentiation operator of the external command bc as:

bash:$ echo 2^100 | bc 1267650600228229401496703205376 

If you want to store the above result in a variable you can use command substitution either via the $() syntax:

var=$(echo 2^100 | bc) 

or the older backtick syntax:

var=`echo 2^100 | bc` 

Note that command substitution is not the same as arithmetic expansion:

$(( )) # arithmetic expansion $( )   # command substitution 

Answer 2

Various ways:

Bash

echo $((10**2)) 

Awk

awk 'BEGIN{print 10^2}'  # POSIX standard awk 'BEGIN{print 10**2}' # GNU awk extension 

bc

echo '10 ^ 2' | bc 

dc

dc -e '10 2 ^ p'