Generate a Random Output from the List of Multiplicities of a Number X up to a MAX Number Y?

Question

Using a bash script, I want to choose a random number from such a list: [0, X, 2X, 3X, 4X, ..., Y] where Y=k*X and k is an integer. X and Y are just some input numbers by the user. To clarify the question, here is an example:

X=2
#Y=10*X
Y=20
# The <desired_command> to choose a random number from [0, 2, 4, 6, 8, ..., 20] --> sample output=12
desired_command

How can I do this?

Possible duplicate of [How to generate random number in Bash?](https://stackoverflow.com/questions/1194882/how-to-generate-random-number-in-bash) — jonrsharpe, Oct 22 '19 at 09:22
@jonrsharpe I want to solve the alignment issue here not the range. I think this link doesn't tackle with the alignment problem — Arghavan Mohammadhassani, Oct 22 '19 at 09:46
The answer on the duplicate **also** shows you how to get it within a range, which I think is what you mean by "alignment problem". This is just basic arithmetic - get a number in the range `[0, Y / X]` using modulo (`%`), then multiply by `X`. — jonrsharpe, Oct 22 '19 at 09:47
`[0, X, 2X, 3X, 4X, ..., Y]` - just multiply the random number from the list `[0,1,2,3,4...Y]` by `X`?? — KamilCuk, Oct 22 '19 at 09:50
`of these numbers can be` - your post if very unclear. Is this somehow a generated list? What examples can be given for `X` and `Y`? Do you want to generate a list of multiplicities of a number up to a given number and choose a random number from that list? Is the list of the numbers in random order? The "aligned to a fixed value" I believe is the most confusing part, can you rephrase it? — KamilCuk, Oct 22 '19 at 10:53
@KamilCuk I want to generate a list of multiplicities of a number (i.e. X) up to a given number (i.e. Y) and choose a random number from that list (i.e. the desired output) — Arghavan Mohammadhassani, Oct 22 '19 at 11:17

Mohammad Fahim Abrar · Accepted Answer · 2019-10-22T10:55:12.800

1

You can use this command:

echo $(($(shuf -i 0-$((Y/X)) -n1)*X))

edited Oct 22 '19 at 10:55

answered Oct 22 '19 at 10:53

Mohammad Fahim Abrar

519
3
18

Is it better to use this shuf command or the RANDOM variable? – Arghavan Mohammadhassani Oct 22 '19 at 11:23

score 1 · Answer 2 · answered Oct 22 '19 at 11:20

1

# x positive integer
# y positive integer y >= x
x=11
y=34
echo $(((RANDOM % (y/x+1)) * x))

answered Oct 22 '19 at 11:20

Kamoo

832
4
11

Generate a Random Output from the List of Multiplicities of a Number X up to a MAX Number Y?

2 Answers2