Math using dc

dc is one of the oldest language on Unix.

It is using the reverse polish notation, which means that you are first stacking numbers, then operations. For example 1+1 is written as 1 1+.

To print an element from the top of the stack use command p

echo '2 3 + p' | dc
5

or

dc <<< '2 3 + p'
5

You can print the top element many times

dc <<< '1 1 + p 2 + p'
2
4

For negative numbers use \_ prefix

dc <<< '_1 p'
-1

You can also use capital letters from A to F for numbers between 10 and 15 and . as a decimal point

dc <<< 'A.4 p'
10.4

dc is using abitrary precision which means that the precision is limited only by the available memory. By default the precision is set to 0 decimals

dc <<< '4 3 / p'
1

We can increase the precision using command k. 2k will use

dc <<< '2k 4 3 / p'
1.33

dc <<< '4k 4 3 / p'
1.3333

You can also use it over multiple lines

dc << EOF
1 1 +
3 *
p
EOF
6

bc is a preprocessor for dc.