How to get the difference between numbers using dc?

Question

Input:

> printf 1\n\2\n3\n
1
2
3

Desired output:

0
1
1

Typing printf 1\n\2\n3\n | dc -e '-p' the output is:

dc: stack empty
dc: stack empty

Answer 1

You can pipe the entire set of commands directly to dc.

printf "1 2 3 - - p" | dc

If you'd like to subtract an arbitrary stack you can use a macro.

printf "%s [-z1<r]srz1<rp" "<insert numbers here>" | dc

So for example

printf "%s [-z1<r]srz1<rp" "100 5 2 1" | dc
96

The macro does the following:

• [ Start macro
• - Subtract top two numbers and push back to stack
• z1<r Push stack size to stack and 1, then compare LESSTHAN, if true run r macro
• ]sr End of macro, store in register r
• z1<r Check if stack contains elements by testing 1 < Stack Size

• p Print result.

• `