Need to convert a base 10 integer in a base 2 one? Or, at any rate, convert a number from one numeration system to another? In Ubuntu, the bc utility already integrates these features. It is usually already installed, so you don't have to anything special.

**Simply run bc, and enter the following commands:**

ibase=10 obase=2

Then, all subsequent number inputs will be simply converted to their base-2 representation.

If you want to get a conversion straight ahead, without going through the opening of bc, just enter the following from a terminal:

echo 'obase=2; ibase=10; 123' | bc

which will convert the number 123 from base 10 to base 2.

Of course, 2 and 10 can be replaced with any other possible base!