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Linux Calulator bc

2018年02月07日

Overview

bc command is a linux command line calculator, can do basic mathematical calculations, like Integer, floating calculations.

usage: bc [options] [file ...]
  -h  --help         print this usage and exit
  -i  --interactive  force interactive mode
  -l  --mathlib      use the predefined math routines
  -q  --quiet        don't print initial banner
  -s  --standard     non-standard bc constructs are errors
  -w  --warn         warn about non-standard bc constructs
  -v  --version      print version information and exit

The bc command supports the following features:

  1. Arithmetic operators
  2. Increment or Decrement operators
  3. Assignment operators
  4. Comparison or Relational operators
  5. Logical or Boolean operators
  6. Math functions
  7. Conditional statements
  8. Iterative statements

Usage

1. Arithmetic operators

$ a=2
$ b=10
$ echo "$a+$b" | bc
12
$ echo "$a-$b" | bc
-8
$ echo "$a*$b" | bc
20
$ echo "$a/$b" | bc
0
$ echo "$a^$b" | bc
1024
$ echo "sqrt(10)" | bc
3
$ echo "scale=2;sqrt(10)" | bc
3.16

bc 可以用 scale 保留小数位, only supports the /, sqrt, if you want to use it as follows:

$ echo "scale=2;3.333+4.444" | bc
7.777
$ echo "scale=2;(3.333+4.444)/1" | bc
7.77

From above, it not support math rounding, there is a workaround as follows:

$ echo "scale=2;(7.777+0.005)/1" | bc
7.78

2. Assignment Operators

  • var = value : Assign the vale to the variable
  • var += value : similar to var = var + value
  • var -= value : similar to var = var – value
  • var *= value : similar to var = var * value
  • var /= value : similar to var = var / value
  • var ^= value : similar to var = var ^ value
  • var %= value : similar to var = var % value
$ echo "var=10;var+=9;var" | bc
19

3. Increment and Decrement Operators

$ echo "var=10;var++" | bc
10
$ echo "var=10;++var" | bc
11
$ echo "var=10;var--" | bc
10
$ echo "var=10;--var" | bc
9

4. Comparison or Relational Operators

These are used to compare 2 numbers. If the comparison is true, then result is 1. Otherwise(false), returns 0.

Operators: <,<=,>,>=,==,!=.

$ echo "10>=10.0" | bc
1
$ echo "10!=10.0" | bc
0

5. Logical or Boolean Operators

$ echo "10 && 5" | bc
1
$ echo "0 || 0" | bc
0
$ echo "!0" | bc
bash: !0: event not found
$ echo "! 0" | bc
1

6.Mathematical Functions

$ echo "length(1.2345)" | bc -l
5
$ echo "scale(1.2345)" | bc -l
4

进制转换

$ echo "ibase=10;obase=2;15" | bc -l
1111
$ echo "ibase=2;1111" | bc
15

7. Conditional Statements

$ echo 'n=8;m=10;if(n>m) print "n is greater" else print "m is greater" ' | bc -l
m is greater