How to generate a random string in Ruby
RubyRandomPasswordsRuby Problem Overview
I'm currently generating an 8-character pseudo-random uppercase string for "A" .. "Z":
value = ""; 8.times{value << (65 + rand(25)).chr}
but it doesn't look clean, and it can't be passed as an argument since it isn't a single statement. To get a mixed-case string "a" .. "z" plus "A" .. "Z", I changed it to:
value = ""; 8.times{value << ((rand(2)==1?65:97) + rand(25)).chr}
but it looks like trash.
Does anyone have a better method?
Ruby Solutions
Solution 1 - Ruby
(0...8).map { (65 + rand(26)).chr }.join
I spend too much time golfing.
(0...50).map { ('a'..'z').to_a[rand(26)] }.join
And a last one that's even more confusing, but more flexible and wastes fewer cycles:
o = [('a'..'z'), ('A'..'Z')].map(&:to_a).flatten
string = (0...50).map { o[rand(o.length)] }.join
If you want to generate some random text then use the following:
50.times.map { (0...(rand(10))).map { ('a'..'z').to_a[rand(26)] }.join }.join(" ")
this code generates 50 random word string with words length less than 10 characters and then join with space
Solution 2 - Ruby
Why not use SecureRandom?
require 'securerandom'
random_string = SecureRandom.hex
# outputs: 5b5cd0da3121fc53b4bc84d0c8af2e81 (i.e. 32 chars of 0..9, a..f)
SecureRandom also has methods for:
- base64
- random_bytes
- random_number
see: http://ruby-doc.org/stdlib-1.9.2/libdoc/securerandom/rdoc/SecureRandom.html
Solution 3 - Ruby
I use this for generating random URL friendly strings with a guaranteed maximum length:
string_length = 8
rand(36**string_length).to_s(36)
It generates random strings of lowercase a-z and 0-9. It's not very customizable but it's short and clean.
Solution 4 - Ruby
This solution generates a string of easily readable characters for activation codes; I didn't want people confusing 8 with B, 1 with I, 0 with O, L with 1, etc.
# Generates a random string from a set of easily readable characters
def generate_activation_code(size = 6)
charset = %w{ 2 3 4 6 7 9 A C D E F G H J K M N P Q R T V W X Y Z}
(0...size).map{ charset.to_a[rand(charset.size)] }.join
end
Solution 5 - Ruby
Others have mentioned something similar, but this uses the URL safe function.
require 'securerandom'
p SecureRandom.urlsafe_base64(5) #=> "UtM7aa8"
p SecureRandom.urlsafe_base64 #=> "UZLdOkzop70Ddx-IJR0ABg"
p SecureRandom.urlsafe_base64(nil, true) #=> "i0XQ-7gglIsHGV2_BNPrdQ=="
The result may contain A-Z, a-z, 0-9, “-” and “_”. “=” is also used if padding is true.
Solution 6 - Ruby
Since Ruby 2.5, it's really easy with SecureRandom.alphanumeric
:
len = 8
SecureRandom.alphanumeric(len)
=> "larHSsgL"
It generates random strings containing A-Z, a-z and 0-9 and therefore should be applicable in most use-cases. And they are generated randomly secure, which might be a benefit, too.
This is a benchmark to compare it with the solution having the most upvotes:
require 'benchmark'
require 'securerandom'
len = 10
n = 100_000
Benchmark.bm(12) do |x|
x.report('SecureRandom') { n.times { SecureRandom.alphanumeric(len) } }
x.report('rand') do
o = [('a'..'z'), ('A'..'Z'), (0..9)].map(&:to_a).flatten
n.times { (0...len).map { o[rand(o.length)] }.join }
end
end
user system total real
SecureRandom 0.429442 0.002746 0.432188 ( 0.432705)
rand 0.306650 0.000716 0.307366 ( 0.307745)
So the rand
solution only takes about 3/4 of the time of SecureRandom
. That might matter if you generate a lot of strings, but if you just create some random string from time to time I'd always go with the more secure implementation since it is also easier to call and more explicit.
Solution 7 - Ruby
[*('A'..'Z')].sample(8).join
Generate a random 8 letter string (e.g. NVAYXHGR)
([*('A'..'Z'),*('0'..'9')]-%w(0 1 I O)).sample(8).join
Generate a random 8 character string (e.g. 3PH4SWF2), excludes 0/1/I/O. Ruby 1.9
Solution 8 - Ruby
I can't remember where I found this, but it seems like the best and the least process intensive to me:
def random_string(length=10)
chars = 'abcdefghjkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ0123456789'
password = ''
length.times { password << chars[rand(chars.size)] }
password
end
Solution 9 - Ruby
require 'securerandom'
SecureRandom.urlsafe_base64(9)
Solution 10 - Ruby
If you want a string of specified length, use:
require 'securerandom'
randomstring = SecureRandom.hex(n)
It will generate a random string of length 2n
containing 0-9
and a-f
Solution 11 - Ruby
Array.new(n){[*"0".."9"].sample}.join
,
where n=8
in your case.
Generalized: Array.new(n){[*"A".."Z", *"0".."9"].sample}.join
, etc.
Solution 12 - Ruby
Here is one line simple code for random string with length 8:
random_string = ('0'..'z').to_a.shuffle.first(8).join
You can also use it for random password having length 8:
random_password = ('0'..'z').to_a.shuffle.first(8).join
Solution 13 - Ruby
require 'sha1'
srand
seed = "--#{rand(10000)}--#{Time.now}--"
Digest::SHA1.hexdigest(seed)[0,8]
Solution 14 - Ruby
Ruby 1.9+:
ALPHABET = ('a'..'z').to_a
#=> ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]
10.times.map { ALPHABET.sample }.join
#=> "stkbssowre"
# or
10.times.inject('') { |s| s + ALPHABET.sample }
#=> "fdgvacnxhc"
Solution 15 - Ruby
Here is one simple code for random password with length 8:
rand_password=('0'..'z').to_a.shuffle.first(8).join
Solution 16 - Ruby
Be aware: rand
is predictable for an attacker and therefore probably insecure. You should definitely use SecureRandom if this is for generating passwords. I use something like this:
length = 10
characters = ('A'..'Z').to_a + ('a'..'z').to_a + ('0'..'9').to_a
password = SecureRandom.random_bytes(length).each_char.map do |char|
characters[(char.ord % characters.length)]
end.join
Solution 17 - Ruby
Another method I like to use:
rand(2**256).to_s(36)[0..7]
Add ljust
if you are really paranoid about the correct string length:
rand(2**256).to_s(36).ljust(8,'a')[0..7]
Solution 18 - Ruby
SecureRandom.base64(15).tr('+/=lIO0', 'pqrsxyz')
Something from Devise
Solution 19 - Ruby
I think this is a nice balance of conciseness, clarity and ease of modification.
characters = ('a'..'z').to_a + ('A'..'Z').to_a
# Prior to 1.9, use .choice, not .sample
(0..8).map{characters.sample}.join
Easily modified
For example, including digits:
characters = ('a'..'z').to_a + ('A'..'Z').to_a + (0..9).to_a
Uppercase hexadecimal:
characters = ('A'..'F').to_a + (0..9).to_a
For a truly impressive array of characters:
characters = (32..126).to_a.pack('U*').chars.to_a
Solution 20 - Ruby
Just adding my cents here...
def random_string(length = 8)
rand(32**length).to_s(32)
end
Solution 21 - Ruby
You can use String#random
from the Facets of Ruby Gem facets
.
It basically does this:
class String
def self.random(len=32, character_set = ["A".."Z", "a".."z", "0".."9"])
characters = character_set.map { |i| i.to_a }.flatten
characters_len = characters.length
(0...len).map{ characters[rand(characters_len)] }.join
end
end
Solution 22 - Ruby
This solution needs external dependency, but seems prettier than another.
- Install gem faker
Faker::Lorem.characters(10) # => "ang9cbhoa8"
Solution 23 - Ruby
I was doing something like this recently to generate an 8 byte random string from 62 characters. The characters were 0-9,a-z,A-Z. I had an array of them as was looping 8 times and picking a random value out of the array. This was inside a Rails app.
str = ''
8.times {|i| str << ARRAY_OF_POSSIBLE_VALUES[rand(SIZE_OF_ARRAY_OF_POSSIBLE_VALUES)] }
The weird thing is that I got good number of duplicates. Now randomly this should pretty much never happen. 62^8 is huge, but out of 1200 or so codes in the db i had a good number of duplicates. I noticed them happening on hour boundaries of each other. In other words I might see a duple at 12:12:23 and 2:12:22 or something like that...not sure if time is the issue or not.
This code was in the before create of an ActiveRecord object. Before the record was created this code would run and generate the 'unique' code. Entries in the DB were always produced reliably, but the code (str
in the above line) was being duplicated much too often.
I created a script to run through 100000 iterations of this above line with small delay so it would take 3-4 hours hoping to see some kind of repeat pattern on an hourly basis, but saw nothing. I have no idea why this was happening in my Rails app.
Solution 24 - Ruby
Given:
chars = [*('a'..'z'),*('0'..'9')].flatten
Single expression, can be passed as an argument, allows duplicate characters:
Array.new(len) { chars.sample }.join
Solution 25 - Ruby
My favorite is (:A..:Z).to_a.shuffle[0,8].join
. Note that shuffle requires Ruby > 1.9.
Solution 26 - Ruby
I like Radar's answer best, so far, I think. I'd tweak a bit like this:
CHARS = ('a'..'z').to_a + ('A'..'Z').to_a
def rand_string(length=8)
s=''
length.times{ s << CHARS[rand(CHARS.length)] }
s
end
Solution 27 - Ruby
''.tap {|v| 4.times { v << ('a'..'z').to_a.sample} }
Solution 28 - Ruby
2 solutions for a random string consisting of 3 ranges:
(('a'..'z').to_a + ('A'..'Z').to_a + (0..9).to_a).sample(8).join
([*(48..57),*(65..90),*(97..122)]).sample(8).collect(&:chr)*""
One Character from each Range.
And if you need at least one character from each range, such as creating a random password that has one uppercase, one lowercase letter and one digit, you can do something like this:
( ('a'..'z').to_a.sample(8) + ('A'..'Z').to_a.sample(8) + (0..9).to_a.sample(8) ).shuffle.join
#=> "Kc5zOGtM0H796QgPp8u2Sxo1"
Solution 29 - Ruby
My 2 cents:
def token(length=16)
chars = [*('A'..'Z'), *('a'..'z'), *(0..9)]
(0..length).map {chars.sample}.join
end
Solution 30 - Ruby
I just write a small gem random_token
to generate random tokens for most use case, enjoy ~
Solution 31 - Ruby
We've been using this on our code:
class String
def self.random(length=10)
('a'..'z').sort_by {rand}[0,length].join
end
end
The maximum length supported is 25 (we're only using it with the default anyway, so hasn't been a problem).
Someone mentioned that 'a'..'z' is suboptimal if you want to completely avoid generating offensive words. One of the ideas we had was removing vowels, but you still end up with WTFBBQ etc.
Solution 32 - Ruby
With this method you can pass in an abitrary length. It's set as a default as 6.
def generate_random_string(length=6)
string = ""
chars = ("A".."Z").to_a
length.times do
string << chars[rand(chars.length-1)]
end
string
end
Solution 33 - Ruby
try this out
def rand_name(len=9)
ary = [('0'..'9').to_a, ('a'..'z').to_a, ('A'..'Z').to_a]
name = ''
len.times do
name << ary.choice.choice
end
name
end
I love the answers of the thread, have been very helpful, indeed!, but if I may say, none of them satisfies my ayes, maybe is the rand() method. it's just doesn't seems right to me, since we've got the Array#choice method for that matter.
Solution 34 - Ruby
Here is another method:
- It uses the secure random number generator instead of rand()
- Can be used in URLs and file names
- Contains uppercase, lowercase characters and numbers
- Has an option not to include ambiguous characters I0l01
Needs require "securerandom"
def secure_random_string(length = 32, non_ambiguous = false)
characters = ('a'..'z').to_a + ('A'..'Z').to_a + ('0'..'9').to_a
%w{I O l 0 1}.each{ |ambiguous_character|
characters.delete ambiguous_character
} if non_ambiguous
(0...length).map{
characters[ActiveSupport::SecureRandom.random_number(characters.size)]
}.join
end
Solution 35 - Ruby
If you are on a UNIX and you still must use Ruby 1.8 (no SecureRandom) without Rails, you can also use this:
random_string = `openssl rand -base64 24`
Note this spawns new shell, this is very slow and it can only be recommended for scripts.
Solution 36 - Ruby
Another trick that works with Ruby 1.8+ and is fast is:
>> require "openssl"
>> OpenSSL::Random.random_bytes(20).unpack('H*').join
=> "2f3ff53dd712ba2303a573d9f9a8c1dbc1942d28"
It get's you random hex string. Similar way you should be able to generate base64 string ('M*').
Solution 37 - Ruby
This is based on a few other answers, but it adds a bit more complexity:
def random_password
specials = ((32..47).to_a + (58..64).to_a + (91..96).to_a + (123..126).to_a).pack('U*').chars.to_a
numbers = (0..9).to_a
alpha = ('a'..'z').to_a + ('A'..'Z').to_a
%w{i I l L 1 O o 0}.each{ |ambiguous_character|
alpha.delete ambiguous_character
}
characters = (alpha + specials + numbers)
password = Random.new.rand(8..18).times.map{characters.sample}
password << specials.sample unless password.join =~ Regexp.new(Regexp.escape(specials.join))
password << numbers.sample unless password.join =~ Regexp.new(Regexp.escape(numbers.join))
password.shuffle.join
end
Essentially it ensures a password that is 8 - 20 characters in length, and which contains at least one number and one special character.
Solution 38 - Ruby
10.times do
alphabet = ('a'..'z').to_a
string += alpha[rand(alpha.length)]
end
Solution 39 - Ruby
For devise secure_validatable you can use this
(0...8).map { ([65, 97].sample + rand(26)).chr }.push(rand(99)).join
Solution 40 - Ruby
Here is a improve of @Travis R answer:
def random_string(length=5)
chars = 'abdefghjkmnpqrstuvwxyzABDEFGHJKLMNPQRSTUVWXYZ'
numbers = '0123456789'
random_s = ''
(length/2).times { random_s << numbers[rand(numbers.size)] }
(length - random_s.length).times { random_s << chars[rand(chars.size)] }
random_s.split('').shuffle.join
end
At @Travis R answer chars and numbers were together, so sometimes random_string
could return only numbers or only characters. With this improve at least half of random_string
will be characters and the rest are numbers. Just in case if you need a random string with numbers and characters
Solution 41 - Ruby
To make your first into one statement:
(0...8).collect { |n| value << (65 + rand(25)).chr }.join()
Solution 42 - Ruby
`pwgen 8 1`.chomp
Solution 43 - Ruby
Create an empty string or a pre-fix if require:
myStr = "OID-"
Use this code to populate the string with random numbers:
begin; n = ((rand * 43) + 47).ceil; myStr << n.chr if !(58..64).include?(n); end while(myStr.length < 12)
Notes:
(rand * 43) + 47).ceil
It will generate random numbers from 48-91 (0,1,2..Y,Z)
!(58..64).include?(n)
It is used to skip special characters (as I am not interested to include them)
while(myStr.length < 12)
It will generate total 12 characters long string including prefix.
Sample Output:
"OID-XZ2J32XM"
Solution 44 - Ruby
Here's a solution that is flexible and allows dups:
class String
# generate a random string of length n using current string as the source of characters
def random(n)
return "" if n <= 0
(chars * (n / length + 1)).shuffle[0..n-1].join
end
end
Example:
"ATCG".random(8) => "CGTGAAGA"
You can also allow a certain character to appear more frequently:
"AAAAATCG".random(10) => "CTGAAAAAGC"
Explanation: The method above takes the chars of a given string and generates a big enough array. It then shuffles it, takes the first n items, then joins them.
Solution 45 - Ruby
Array.new(8).inject(""){|r|r<<('0'..'z').to_a.shuffle[0]} # 57
(1..8).inject(""){|r|r<<('0'..'z').to_a.shuffle[0]} # 51
e="";8.times{e<<('0'..'z').to_a.shuffle[0]};e # 45
(1..8).map{('0'..'z').to_a.shuffle[0]}.join # 43
(1..8).map{rand(49..122).chr}.join # 34
Solution 46 - Ruby
a='';8.times{a<<[*'a'..'z'].sample};p a
or
8.times.collect{[*'a'..'z'].sample}.join
Solution 47 - Ruby
Use 'SafeRandom' Gem GithubLink
It will provide the easiest way to generate random values for Rails2, Rails 3, Rails 4, Rails 5 compatible.
Solution 48 - Ruby
The following worked well for me
def generate_random_password(min_length, max_length)
length = SecureRandom.random_number(max_length - min_length) + min_length
character_sets = [
('a'..'z').to_a,
('A'..'Z').to_a,
('0'..'9').to_a,
"~!@^&*()_-+=[]|:;<,>.?".split('')
]
retval = []
#
# Add one character from each set
#
character_sets.each do |character_set|
character = character_set[SecureRandom.random_number(character_set.count)]
retval.push character
end
#
# Fill the rest of the password with a random character from a random set
#
i = character_sets.count - 1
while i < length
character_set = character_sets[SecureRandom.random_number(character_sets.count)]
character = character_set[SecureRandom.random_number(character_set.count)]
retval.push character
i += 1
end
retval.shuffle.join
end
Solution 49 - Ruby
This is almost as ugly but perhaps as step in right direction?
(1..8).map{|i| ('a'..'z').to_a[rand(26)]}.join
Solution 50 - Ruby
In ruby 1.9 one can use Array's choice method which returns random element from array
Solution 51 - Ruby
I don't know ruby, so I can't give you the exact syntax, but I would set a constant string with the list of acceptable characters, then use the substring operator to pick a random character out of it.
The advantage here is that if the string is supposed to be user-enterable, then you can exclude easily confused characters like l and 1 and i, 0 and O, 5 and S, etc.