a mod b

You can use mod to round a decimal number down to the nearest whole number.

For example:

If you wanted to use the command random to generate a whole number between 0 and 6, you could put this in a script:-

_rand = random 6
_num = _rand - (_rand mod 1)

Addendum to the above comment:

If you wanted to use the random command to generate a whole number between 0 and 6 inclusive (i.e. 0 or 1 or 2 or 3 or 4 or 5 or 6) you would put this in a script:

_rand = random 7
_num = _rand - (_rand mod 1)

since the upper limit provided to the random command is exclusive, i.e. random 7 will never generate 7, but it could return 0, in which case your code should take account of the possibility.

Thanks to Mr. Peanut for providing this info.