roll(1) - Linux man page
Name
roll - rolls a user-defined dice sequence
Synopsis
roll [-vhp] [--version] expression
Description
roll Rolls a user-defined dice sequence. The dices to roll are defined using dN where N is the number of sides. Dices can be rolled multiple times by prepending the number of repetitions (e.g., 3d6) and used in simple mathematical expressions (e.g., 2d8+4).
Options
--help, -h
- help
- --positive, -p
- allow only positive results
- --verbose, -v
- verbose (displays the result for each roll)
- --version
- prints the version of the program
Expressions
Expressions are in dice notation (also known as dice algebra, common dice notation or RPG dice notation)
Die rolls are expressed in the form NdX or NDX where N is the number of dices (1 if omitted) and X the number of dice faces.
If the final number is omitted, it is assumed to be a six.
To this basic notation, an additive modifier can be appended, yielding expressions of the form, NdX+C. The plus can be replaced by a minus sign ("-") for subtraction. C is a number to be subtracted from the final total.
See: http://en.wikipedia.org/wiki/Dice_notation
Percentile dice (d%)
Often, the variable X in the above notation will be "%". Although a 100-sided die does exist, it is both more common and more uniformly random to use a combination of two ten-sided dice known as percentile dice, where one die represents tens and the other units. A roll of two zeroes means 100.
If you want to roll a single 100-sided die use the "d100" notation.
Multipliers
In some games, the above notation is expanded to allow for a multiplier, as in NdXxC or CxNdX, where "x" or "*" denotes multiplication (can be replaced by "/" for division) and C is a natural number.
Results are rounded up.
Selective results
It is possible to keep only the M highest or lowest dices with the following notation:
- NdXhM: roll N dices with X sides and keep the highest M results (M must be less or equal N)
- NdXlM: roll N dices with X sides and keep the lowest M results (M must be less or equal N)
Examples
3d6 rolls 3 6-sided dices and sums the results
- (can be abbreviated with "3d")
- 1d8 + 3 rolls 1 8-sided die and adds 3
- (can be abbreviated by "d8+3")
- d% rolls 2 10-sided dices: one represents the tens and
- the other units
- 1d6x5 rolls 1 6-sided dice and multiplies the result by 5
- 1d6 / 2 rolls 1 6-sided dice and divides the result by 2 (1d3)
- 4d6h3 rolls 4 6-sided dices and keeps the 3 highest results
- 1d6 / 2 rolls 1 6-sided dice and divides the result by 2 (1d3)
- (discarding the lowest)
Grammar (EBNF)
expression := term { "+" term | "-" term } .
- term := number | factor [ ("*"|"/") number |
- number ("*"|"/") factor | "(" expression ")" .
- factor := number dice [ ("h"|"H"|"l"|"L") number ] | dice .
- dice := "d" | "D" [ number | "%" ] .
See Also
random(3)
Exit Status
roll returns a zero exist status if it finds no error in the supplied expresssion
Bugs
Please report bugs to: Matteo Corti (matteo.corti (at) gmail.com )
Author
Matteo Corti (matteo.corti (at) gmail.com)