Linux Command BC(Basic Calculator)

BC(Basic Calculator)

What is 'bc'

• 'bc' (basic calculator) is a command line calculator. It reads "expressions to be evaluated" from stdin and sends output to stdout. So you can pipe the output of any linux command to 'bc' for further calculations and you can pipe the output to any other linux command.
• Since 'bc' reads input from stdin, the common usage is of the form
  

Why 'bc':

• You dont have to load a GUI calculator to do simple calculations.
• Precision can be set to any value (most of the graphical calculators has a precision upto 10 digits). Precision is limitted only by the processing power of your computer. You can find the value of pi upto 1000 decimal places within 1.5 mins with a normal computer.
• Available by default with all flavours of linux by default

1.Example for Addition, Subtraction, Multiplication, Division, Power, square root

The scale (number of digits after decimal point), by default is set to 2

sunitha@sunitha-lappy:~$ bc <<< "scale=2;10/2"
5.00
sunitha@sunitha-lappy:~$ bc <<< "2^3"
8
sunitha@sunitha-lappy:~$ bc <<< "scale=20;sqrt(10)"
3.16227766016837933199

2.Grouping - using parenthesis

sunitha@sunitha-lappy:~$ bc <<< "10+(2*3)"
16

3.Relational Expressions - <, >, >=, <=, ==, !=

sunitha@sunitha-lappy:~$ bc <<< "5<3"
0
sunitha@sunitha-lappy:~$ bc <<< "5>3"
1
sunitha@sunitha-lappy:~$ bc <<< "5>=3"
1
sunitha@sunitha-lappy:~$ bc <<< "5<=3"
0
sunitha@sunitha-lappy:~$ bc <<< "5==3"
0
sunitha@sunitha-lappy:~$ bc <<< "5!=3"
1

4.Bitwise Operations:

Base - obase, ibase

Base conversion -- Hexadecimal to Decimal

sunitha@sunitha-lappy:~$ bc <<< "obase=16;124"
7C

Base conversion -- Decimal to Hexadecimal

sunitha@sunitha-lappy:~$ bc <<< "ibase=16;7C"
124

Hexadecimal calculation

sunitha@sunitha-lappy:~$ bc <<< "obase=16;ibase=16;7C+F"
8B

sunitha@sunitha-lappy:~$ bc <<< "ibase=16;obase=10;7C+F"
8B

Binary calculation:

sunitha@sunitha-lappy:~$ bc <<< "obase=2;28"
11100
sunitha@sunitha-lappy:~$ bc <<< "obase=2;ibase=2;11100+10011"
101111

5.MATH LIBRARY

       If bc is invoked with the -l option, math library gets preloaded, making a lot more math functions available to us.

Note: Default scale is set to 20 when bc is started with -l option

(a) sine,cos,tan and arctangent

Note: pi can be calculated using the formula, pi=4*arctangent(1)

sunitha@sunitha-lappy:~$ bc -l <<< "pi=4*a(1);pi"
3.14159265358979323844
sunitha@sunitha-lappy:~$ bc -l <<< "pi=4*a(1);s(pi/2)"
1.00000000000000000000
sunitha@sunitha-lappy:~$ bc -l <<< "pi=4*a(1);c(pi/2)"
.00000000000000000001

(b)exponential and logarithmic functions

sunitha@sunitha-lappy:~$ bc -l <<< "l(e(10))"
9.99999999999999999999

Some Cool tips

* Arbitrary precision (scale)

bc has a default scale of 0, which is quite annoyoing as bc <<< 3/2 gives 1 instead of 1.5.  bc -l would solve this issue

sunitha@sunitha-laptop:~$ bc <<< 3/2 -l
1.50000000000000000000
 

  The default scale is 20. But if you need any arbitrary precision, say you want the default scale to be 5 whenever you invoke bc, follow this

In your .bashrc in your home directory add "export BC_ENV_ARGS=~/.bc"

Then create the file named ".bc" in your home directory, with the following one line

        scale=5

Now, bc <<< 5/3 gives 1.66666

* Alarm

To start audacious (the default music player that comes with ubuntu) after 8 hrs (to server as an alarm)

sleep `bc <<< 8*60*60`; audacious -p

For more info about 'bc', refer http://www.gnu.org/software/bc/manual/html_mono/bc.html