Difference between revisions of "Dc versus bc"
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Q: What is the difference between `dc` and `bc`? | Q: What is the difference between `dc` and `bc`? | ||
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$ echo "4*a(1)" | bc -l # Note that 'a' is the arctangent function. | $ echo "4*a(1)" | bc -l # Note that 'a' is the arctangent function. | ||
3.14159265358979323844 | 3.14159265358979323844 | ||
+ | |||
+ | === Using bc in bash === | ||
+ | |||
+ | Trying to do even trivial math with `expr` is a pain. Bash sucks. To set a variable to an expression you end up having to write code like this: | ||
+ | |||
+ | <pre> | ||
+ | SIZE_MB=$(bc <<< '50000000/(1024*1024)') | ||
+ | </pre> |
Revision as of 19:44, 6 December 2007
Q: What is the difference between `dc` and `bc`?
A: The `dc` command is a Reverse-Polish Notation basic arithmetic calculator. It does not support common trigonometric or scientific functions. Examples of `dc`:
$ dc -e "25.5 2 * p" 51.0 $ dc -e "3 2 ^ p" 9 $ dc -e "9 v p" # Note that 'v' is the sqrt operator. 3
The `bc` command is a front-end to `dc` (althugh the GNU `bc` is completely separate and does not compile to `dc` bytecode). So `bc` is similar to `dc`, but adds a C-like syntax; standard infix notation. By default it does not include trig or other common math functions, but you include these by using the '-l' option. Examples of `bc`:
$ echo "scale=5; 10 / (1.5 * 2)" | bc # Note that you have to set scale to see decimals. 3.33333 $ echo "10 / (1.5 * 2)" | bc # The default scale is 0. 3 $ echo "10 / (1.5 * 2)" | bc -l # Note that '-l' option automatically sets scale to 20. 3.33333333333333333333 $ echo "4*a(1)" | bc -l # Note that 'a' is the arctangent function. 3.14159265358979323844
Using bc in bash
Trying to do even trivial math with `expr` is a pain. Bash sucks. To set a variable to an expression you end up having to write code like this:
SIZE_MB=$(bc <<< '50000000/(1024*1024)')