How to generate a random string in Ruby

Question

I m currently generating an 8-character pseudo-random uppercase string for  A      Z    value       8 times value   lt  lt   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  lt  lt    rand 2   1 65 97    rand 25   chr    but it looks like trash   Does anyone have a better method

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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

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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

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Ruby 1 9    ALPHABET     a    z   to a    gt    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    gt   stkbssowre     or  10 times inject        s  s   ALPHABET sample      gt   fdgvacnxhc

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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  lt  lt  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

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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

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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

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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  amp  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     gt   Kc5zOGtM0H796QgPp8u2Sxo1

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tap   v  4 times   v  lt  lt    a    z   to a sample

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This is almost as ugly but perhaps as step in right direction     1  8  map  i    a    z   to a rand 26    join

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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  lt  lt  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

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Use  SafeRandom  Gem GithubLink  It will provide the easiest way to generate random values for Rails2  Rails 3  Rails 4  Rails 5 compatible

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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

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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

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For devise secure validatable you can use this   0   8  map     65  97  sample   rand 26   chr   push rand 99   join

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require  sha1  srand seed    --  rand 10000  --  Time now --  Digest  SHA1 hexdigest seed  0 8

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Given   chars       a    z      0    9    flatten   Single expression  can be passed as an argument  allows duplicate characters   Array new len    chars sample   join

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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  amp  to a  flatten string    0   50  map   o rand o length     join

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require  securerandom  SecureRandom urlsafe base64 9

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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  amp  to a  flatten string    0   50  map   o rand o length     join

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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

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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  amp  to a  flatten string    0   50  map   o rand o length     join

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Here is one simple code for random password with length 8   rand password   0    z   to a shuffle first 8  join

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To make your first into one statement    0   8  collect    n  value   lt  lt   65   rand 25   chr   join

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In ruby 1 9 one can use Array s choice method which returns random element from array

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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

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a    8 times a lt  lt    a    z   sample  p a   or  8 times collect    a    z   sample  join

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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  lt  lt  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

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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  lt  lt  CHARS rand CHARS length       s end

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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  lt  lt  specials sample unless password join    Regexp new Regexp escape specials join     password  lt  lt  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

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Another trick that works with Ruby 1 8  and is fast is    gt  gt  require  openssl   gt  gt  OpenSSL  Random random bytes 20  unpack  H    join   gt   2f3ff53dd712ba2303a573d9f9a8c1dbc1942d28    It get s you random hex string  Similar way you should be able to generate base64 string   M

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Here is a improve of  Travis R answer    def random string length 5      chars    abdefghjkmnpqrstuvwxyzABDEFGHJKLMNPQRSTUVWXYZ      numbers    0123456789      random s           length 2  times   random s  lt  lt  numbers rand numbers size          length - random s length  times   random s  lt  lt  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

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Here is one simple code for random password with length 8   rand password   0    z   to a shuffle first 8  join

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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  lt   0      chars    n   length   1   shuffle 0  n-1  join     end end   Example    ATCG  random 8    gt   CGTGAAGA    You can also allow a certain character to appear more frequently    AAAAATCG  random 10    gt   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

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Just adding my cents here     def random string length   8    rand 32  length  to s 32  end

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In ruby 1 9 one can use Array s choice method which returns random element from array

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To make your first into one statement    0   8  collect    n  value   lt  lt   65   rand 25   chr   join

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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

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Since Ruby 2 5  it s really easy with SecureRandom alphanumeric   len   8 SecureRandom alphanumeric len    gt   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  amp  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

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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

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Given   chars       a    z      0    9    flatten   Single expression  can be passed as an argument  allows duplicate characters   Array new len    chars sample   join

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This solution needs external dependency  but seems prettier than another    Install gem faker Faker  Lorem characters 10      gt   ang9cbhoa8

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Ruby 1 9    ALPHABET     a    z   to a    gt    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    gt   stkbssowre     or  10 times inject        s  s   ALPHABET sample      gt   fdgvacnxhc

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Array new n     0    9   sample  join  where n 8 in your case   Generalized  Array new n     A    Z     0    9   sample  join  etc    From   Generate pseudo random string A-Z  0-9

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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

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pwgen 8 1  chomp

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My 2 cents     def token length 16      chars       A    Z       a    z      0  9        0  length  map  chars sample  join   end

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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

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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

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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  lt  lt  chars rand chars size       password end

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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  lt  lt  n chr if   58  64  include  n   end while myStr length  lt  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  lt  12    It will generate total 12 characters long string including prefix   Sample Output    OID-XZ2J32XM

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Here is a improve of  Travis R answer    def random string length 5      chars    abdefghjkmnpqrstuvwxyzABDEFGHJKLMNPQRSTUVWXYZ      numbers    0123456789      random s           length 2  times   random s  lt  lt  numbers rand numbers size          length - random s length  times   random s  lt  lt  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

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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

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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

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require  sha1  srand seed    --  rand 10000  --  Time now --  Digest  SHA1 hexdigest seed  0 8

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Array new 8  inject      r r lt  lt   0    z   to a shuffle 0      57  1  8  inject      r r lt  lt   0    z   to a shuffle 0            51 e    8 times e lt  lt   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

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Others have mentioned something similar  but this uses the  URL safe function   require  securerandom  p SecureRandom urlsafe base64 5     gt   UtM7aa8  p SecureRandom urlsafe base64    gt   UZLdOkzop70Ddx-IJR0ABg  p SecureRandom urlsafe base64 nil  true     gt   i0XQ-7gglIsHGV2 BNPrdQ      The result may contain A-Z  a-z  0-9     -    and                  is also used if padding is true

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This is almost as ugly but perhaps as step in right direction     1  8  map  i    a    z   to a rand 26    join

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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

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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

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My 2 cents     def token length 16      chars       A    Z       a    z      0  9        0  length  map  chars sample  join   end

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Just adding my cents here     def random string length   8    rand 32  length  to s 32  end

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SecureRandom base64 15  tr     lIO0    pqrsxyz     Something from Devise

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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  lt  lt  n chr if   58  64  include  n   end while myStr length  lt  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  lt  12    It will generate total 12 characters long string including prefix   Sample Output    OID-XZ2J32XM

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This is almost as ugly but perhaps as step in right direction     1  8  map  i    a    z   to a rand 26    join

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My favorite is   A   Z  to a shuffle 0 8  join   Note that shuffle requires Ruby   1 9

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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  lt  lt  chars rand chars length-1     end   string end

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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

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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

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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

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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  lt  lt  chars rand chars length-1     end   string end

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Array new 8  inject      r r lt  lt   0    z   to a shuffle 0      57  1  8  inject      r r lt  lt   0    z   to a shuffle 0            51 e    8 times e lt  lt   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

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10 times do    alphabet     a    z   to a   string    alpha rand alpha length   end

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require  sha1  srand seed    --  rand 10000  --  Time now --  Digest  SHA1 hexdigest seed  0 8

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10 times do    alphabet     a    z   to a   string    alpha rand alpha length   end

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SecureRandom base64 15  tr     lIO0    pqrsxyz     Something from Devise

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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  lt  lt  CHARS rand CHARS length       s end

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To make your first into one statement    0   8  collect    n  value   lt  lt   65   rand 25   chr   join

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Another trick that works with Ruby 1 8  and is fast is    gt  gt  require  openssl   gt  gt  OpenSSL  Random random bytes 20  unpack  H    join   gt   2f3ff53dd712ba2303a573d9f9a8c1dbc1942d28    It get s you random hex string  Similar way you should be able to generate base64 string   M

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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

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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  lt  lt  specials sample unless password join    Regexp new Regexp escape specials join     password  lt  lt  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

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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

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For devise secure validatable you can use this   0   8  map     65  97  sample   rand 26   chr   push rand 99   join

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tap   v  4 times   v  lt  lt    a    z   to a sample

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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  lt  lt  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

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I just write a small gem random token to generate random tokens for most use case  enjoy    https   github com sibevin random token

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require  securerandom  SecureRandom urlsafe base64 9

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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

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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

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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

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Use  SafeRandom  Gem GithubLink  It will provide the easiest way to generate random values for Rails2  Rails 3  Rails 4  Rails 5 compatible

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To make your first into one statement    0   8  collect    n  value   lt  lt   65   rand 25   chr   join

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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  lt   0      chars    n   length   1   shuffle 0  n-1  join     end end   Example    ATCG  random 8    gt   CGTGAAGA    You can also allow a certain character to appear more frequently    AAAAATCG  random 10    gt   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

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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

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pwgen 8 1  chomp

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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

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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  lt  lt  CHARS rand CHARS length       s end

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Others have mentioned something similar  but this uses the  URL safe function   require  securerandom  p SecureRandom urlsafe base64 5     gt   UtM7aa8  p SecureRandom urlsafe base64    gt   UZLdOkzop70Ddx-IJR0ABg  p SecureRandom urlsafe base64 nil  true     gt   i0XQ-7gglIsHGV2 BNPrdQ      The result may contain A-Z  a-z  0-9     -    and                  is also used if padding is true

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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

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Since Ruby 2 5  it s really easy with SecureRandom alphanumeric   len   8 SecureRandom alphanumeric len    gt   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  amp  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

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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

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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

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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  lt  lt  chars rand chars length-1     end   string end

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This solution needs external dependency  but seems prettier than another    Install gem faker Faker  Lorem characters 10      gt   ang9cbhoa8

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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  amp  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     gt   Kc5zOGtM0H796QgPp8u2Sxo1

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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  lt  lt  chars rand chars size       password end

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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  amp  to a  flatten string    0   50  map   o rand o length     join

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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

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I just write a small gem random token to generate random tokens for most use case  enjoy    https   github com sibevin random token

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a    8 times a lt  lt    a    z   sample  p a   or  8 times collect    a    z   sample  join

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Array new n     0    9   sample  join  where n 8 in your case   Generalized  Array new n     A    Z     0    9   sample  join  etc    From   Generate pseudo random string A-Z  0-9

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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  lt  lt  CHARS rand CHARS length       s end

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My favorite is   A   Z  to a shuffle 0 8  join   Note that shuffle requires Ruby   1 9

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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

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require  sha1  srand seed    --  rand 10000  --  Time now --  Digest  SHA1 hexdigest seed  0 8

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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

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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  lt  lt  chars rand chars length-1     end   string end

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This is almost as ugly but perhaps as step in right direction     1  8  map  i    a    z   to a rand 26    join

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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

[ruby] How to generate a random string in Ruby

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