Using bc (basic calculator)

**Guest** · 11-03-2009, 09:07 PM

bc is a basic calculator in Linux. Even though it is very simple, it is also very powerful because it allows for arbitrary precision arithmetic.
This tutorial is interactive, you are encouraged to type everything in while reading it!

To start bc, type this into the shell:

Code:

bc

Yes, it is that easy. You should receive a message like this:

Code:

bc 1.06.94
Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.

Now you can type in simple calculations. Try some of these:

Code:

1+1
6*7
8^3
1+2*3
(1+3)*3
2/3

You output should be like this:

Code:

bc does order of operations, just like you would expect.
Everything looks fine, except 2/3 equals 0. Why did this happen?
By default bc does not deal with decimal places. If you want bc to show decimal places, you need to set the scale. Type this into bc:

Code:

scale=10

scale is a variable in bc. When you type that into bc, you make scale equal to ten. Now type this:

Code:

scale

bc should output 10, because that is what scale equals now. Try this:

Code:

2/3

Now you should get this as an output:

Code:

.6666666666

bc calculated 2/3 correctly to ten decimal places.
Now type this in:

Code:

sqrt(2)

bc should output the square root of 2 on your computer:

Code:

1.4142135623

sqrt() is a function in bc.
Now quit bc as follows:

Code:

quit

Now we will execute bc again, but with two flags.

Code:

bc -q -l

The -q makes bc quiet, so you should get no welcome message.
The -l starts bc with a math library, which gives you extra functions to work with. Try this again:

Code:

sqrt(2)

bc should now compute the square root of 2 to 20 decimal places:

Code:

1.41421356237309504880

When you start bc with -l it automatically sets the scale to 20.
bc also has a few new functions. Try this:

Code:

e(1)

bc just calculated Euler's Number to the first power.

Code:

2.71828182845904523536

Type this in:

Code:

s(45)

bc calculates the sine of 45 in radians.

Code:

.85090352453411842486

To calculate cosine use c(), and to calculate arctangent use a()

Now you should know how to use bc for some everyday calculations. What do we do now? If you have programming experience, programming in bc should be very easy. If you don't program, you don't need to read this section.
While loops are like this:

Code:

while (condition) {
calculations
}

Conditions are just like in other programming languages
>, <, <=, >=, ==, !=, etc. will all work in bc
If conditions are like this:

Code:

if (condition) {
calculations
} else {
calculations
}

For a programmer, this should be straightforward and easy to use.
To print things in bc use the print command

Code:

print 1+1

prints 2 to the screen

Code:

print "Hello, CodeCall!\n"

Will print Hello, CodeCall! to the screen followed by a newline.
To read a number use the read() function:

Code:

number=read()

Defining a function is like this:

Code:

define plusone(x) {
x=x+1
return x
}

This function will take x as a number and add one to it.
If you want to run a program in bc, the command looks like this:

Code:

bc program.bc

That's it! Feel free to post any questions, suggestions or comments. +rep is always appreciated.

**John** · 11-03-2009, 09:11 PM

That is very cool! I always found it annoying I couldn't do math in my beloved terminal. I always assumed there was a way, but never cared enough to look into it. +rep