cb is a filter program that does arbitrary radix conversions.
The filter is written in C (C99) for universality. On a typical installation of Linux this should work:
make # create ./cb, run tests
sudo make install # create /usr/bin/cb
cb # get a usage message
echo ff | cb 16 10 # 255
echo 19 | cb 10 2 # 1011
Note: only whole numbers are supported. A number containing a radix separator (decimal point '.' or comma ',') will be converted as two separate numbers.