random pieces of number

[Bachstelze]

I don't think you can generate random numbers directly in Bash. You can use Python:

python -c "import random; print random.randint(1, n)"

will give you a random number between 1 and n (inclusive).

[DanielWaterworth]

It really depends on what you mean by random. Different algorithms will give different distributions and without knowing what you are using it for it is difficult to say of an approach "This will give the best results".

Although the algorithm outlined by varies people above would be the simplest to implement, that of recursively choosing an integer between 1 and the remaining space left. It is a skewed distribution, ie, the first numbers are bigger in general.

Another approach is to generate a number between 1 and the size. This is the amount of numbers you will generate. Set all of the numbers to one, then randomly increment them until the sum is equal to size. This will generate a distribution that is not skewed.