Difference between revisions of "Dc versus bc"

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(New page: Category:Engineering 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 trigono...)
 
 
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[[Category:Engineering]]
 
[[Category:Engineering]]
 
 
Q: What is the difference between `dc` and `bc`?
 
Q: What is the difference between `dc` and `bc`?
  
 
A: The `dc` command is a Reverse-Polish Notation basic arithmetic calculator.
 
A: The `dc` command is a Reverse-Polish Notation basic arithmetic calculator.
 
It does not support common trigonometric or scientific functions.
 
It does not support common trigonometric or scientific functions.
Example of `dc`:
+
Examples of `dc`:
  
 
   $ dc -e "25.5 2 * p"
 
   $ dc -e "25.5 2 * p"
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The `bc` command is a front-end to `dc` (althugh the GNU `bc` is completely separate and does not compile to `dc` bytecode).  
 
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 <strong>not</strong> include trig or other common math functions, but you include these by using the '-l' option. Example of `bc`:
+
So `bc` is similar to `dc`, but adds a C-like syntax; standard infix notation. By default it does <strong>not</strong> include trig or other common math functions, but you include these by using the '-l' option. Examples of `bc`:
  
  $ echo "4*a(1)" | bc -l  # Note that 'a' is the arctangent function.
 
  3.14159265358979323844
 
 
   $ echo "scale=5; 10 / (1.5 * 2)" | bc  # Note that you have to set scale to see decimals.
 
   $ echo "scale=5; 10 / (1.5 * 2)" | bc  # Note that you have to set scale to see decimals.
 
   3.33333
 
   3.33333
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   $ echo "10 / (1.5 * 2)" | bc -l  # Note that '-l' option automatically sets scale to 20.
 
   $ echo "10 / (1.5 * 2)" | bc -l  # Note that '-l' option automatically sets scale to 20.
 
   3.33333333333333333333
 
   3.33333333333333333333
 +
  $ echo "4*a(1)" | bc -l  # Note that 'a' is the arctangent function.
 +
  3.14159265358979323844
 +
  $ bc -l <<< '4*a(1)'      # Same as previous example, but using a herefile idiom.
 +
  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>

Latest revision as of 10:37, 7 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
 $ bc -l <<< '4*a(1)'      # Same as previous example, but using a herefile idiom.
 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)')