Generate random UUID

Question

I need a UUID. Your job is to generate one.

The canonical UUID (Universally Unique IDentifier) is a 32 digit hexadecimal number with hyphens inserted in certain points.The program should output 32 hex digits (128 bits), in the form of xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx (8-4-4-4-12 digits), where x is a random hexadecimal number. Assuming that your language's PRNG is perfect, all valid outputs must have the same probability of being generated.

TL;DR

Generate 32 random hexadecimal digits in the form 8-4-4-4-12 digits. Shortest code wins.

EDIT: Must be hexadecimal. Always generating decimal only is invalid. EDIT 2: No built-ins. These aren't GUIDs, just generic hex digits.

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Example output:

ab13901d-5e93-1c7d-49c7-f1d67ef09198
7f7314ca-3504-3860-236b-cface7891277
dbf88932-70c7-9ae7-b9a4-f3df1740fc9c
c3f5e449-6d8c-afe3-acc9-47ef50e7e7ae
e9a77b51-6e20-79bd-3ee9-1566a95d9ef7
7b10e43c-3c57-48ed-a72a-f2b838d8374b

Input, and standard loopholes are disallowed.

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This is code-golf, so shortest code wins. Also, feel free to ask for clarifications.

Answer 1

Pyth, 20 bytes

j\-msm.HO16*4hdj83 3

Demonstration.

Encodes [1, 0, 0, 0, 2] as 83 in base 3, then adds one and multiplies by four to get the length of each segment. Then makes hex digits and joins on hyphens.

Answer 2

CJam, 26 25 bytes

8 4__C]{{Gmr"%x"e%}*'-}/;

Try it online in the CJam interpreter.

How it works

8 4__C]{              }/   For each I in [8 4 4 4 12]:
        {         }*         Do I times:
         Gmr                   Pseudo-randomly select an integer between 0 and 15.
            "%x"e%             Apply hexadecimal string formatting.
                    '-       Push a hyphen-minus.
                        ;  Discard the last hyphen-minus.

Answer 3

Julia, 80 bytes

h=hex(rand(Uint128),32)
print(h[1:8]"-"h[9:12]"-"h[13:16]"-"h[17:20]"-"h[21:32])

Generate a random 128-bit integer, get its hexidecimal representation as a string padded to 32 digits, and divide that into segments joined with dashes.

Thanks to ConfusedMr_C and kvill for their help!

Answer 4

Perl 5, 43 bytes

Saved 2 bytes thanks to @Xcali!

printf"%04x"."-"x/[2-5]/,rand 2**16for 1..8

Try it online!

Answer 5

PowerShell, 77 69 67 bytes

((8,4,4,4,12)|%{((1..$_)|%{'{0:X}'-f(random(16))})-Join""})-Join"-"

edit: extraneous parens:

((8,4,4,4,12)|%{((1..$_)|%{('{0:X}'-f(random(16)))})-Join""})-Join"-"

edit: was able to remove the trailing .Trim("-") from the original:

(((8,4,4,4,12)|%{((1..$_)|%{('{0:X}'-f(random(16)))})+"-"})-Join"").Trim("-")

It may be clearer with some whitespace given the nature of the flags (-f and -Join). I would still like to lose the final Trim("-"):

(((8,4,4,4,12)|%{((1..$_)|%{('{0:X}' -f (random(16)))}) + "-"}) -Join "").Trim("-")

Or, using the built-in functionality (ala the C# answer above)

'{0}'-f[System.Guid]::NewGuid()

However, it seems a wee bit shortcut-y even if it comes in at 31 bytes.

Answer 6

Python 2, 86 84 bytes

from random import*;print'-'.join('%%0%ix'%i%randint(0,16**i-1)for i in[8,4,4,4,12])

This chains string formatters to make Python format the hex numbers uniquely for each segment.

Ungolfed:

import random

final = []
for i in [8, 4, 4, 4, 12]:               # Iterate through every segment
    max = (16 ** i) - 1                  # This is the largest number that can be
                                         # represented in i hex digits
    number = random.randint(0, max)      # Choose our random segment
    format_string = '%0' + str(i) + 'x'  # Build a format string to pad it with zeroes
    final.append(format_string % number) # Add it to the list

print '-'.join(final)                    # Join every segment with a hyphen and print

This could use some improvement, but I'm proud.

Answer 7

PHP, 69 72 75 bytes

foreach([8,4,4,4,12]as$c)$r[]=rand(".1e$c","1e$c");echo join('-',$r);

This does not output hex digits (a, ... f). They are allowed, but not required by the question body.

No digit group starts with 0 (also not required).

edit: saved 3 bytes thanks to @IsmaelMiguel

Answer 8

R, 63 bytes

x=sample(c(0:9,letters[1:6]),36,1);x[0:3*5+9]='-';cat(x,sep='')

Try it online!

The code first builds a 36 character random string, and then places the four hyphens. It outputs a UUID to stdout.

Answer 9

JavaScript, ES6, 106 bytes

"8-4-4-4-12".replace(/\d+/g, m => {t=0;for(i=0; i<m; i++) {t+=(Math.random()*16|0).toString(16)}return t})

Uses Regex replace. Treats the format string as a count for generating a hex char. Hoisting wherever I can; omitting semicolons where possible.

Answer 10

C#, 65 Bytes

using System;class C{void Main(){Console.Write(Guid.NewGuid());}}

edit: Yes ! C# is shorter than another Language (besides Java) :)

Answer 11

gawk, 86

BEGIN{for(srand();j++<32;printf(j~"^9|13|17|21"?"-":E)"%c",x+(x>10?87:48))x=rand()*16}

You can use this once every second to generate a unique random "UUID". This is because srand() uses the system time in seconds since epoch as argument if there is no argument given.

for n in `seq 100` do awk 'BEGIN{for(srand();j++<32;printf(j~"^9|13|17|21"?"-":E)"%c",x+(x>10?87:48))x=rand()*16}'; sleep 1; done

I think the awk part is rather elegant.

BEGIN{
    srand()
    for(;j++<32;) {
        x=rand()*16
        x+=(x>10?87:48)
        printf "%c", x
        if(j~"^8|12|16|20")printf "-"
    }
}

If you want to use it more often than once every second you can call it in bash like this. Note that the awk part is changed too.

echo `awk 'BEGIN{for(srand('$RANDOM');j++<32;printf(j~"^9|13|17|21"?"-":E)"%c",x+(x>10?87:48))x=rand()*16}'`

The echo is added there to print a new line every time.

Answer 12

K5, 35 bytes

"-"/(0,8+4*!4)_32?`c$(48+!10),65+!6

To generate a hex alphabet I generate a character string (`c$) from a list of digits (48+!10) and the first 6 capital letters (65+!6). An alternate way of generating the digits which is the same length is ,/$!10.

With the string "0123456789ABCDEF" generated, the rest is simple. Select 32 random values from this set (32?), slice (_) the resulting string at 0 8 12 16 20 computed via (0,8+4*!4), and then join the resulting string fragments with dashes ("-"/).

In action:

  "-"/(0,8+4*!4)_32?`c$(48+!10),65+!6
"9550E114-A8DA-9533-1B67-5E1857F355E1"

Answer 13

Kotlin, 175 bytes

fun main(a:Array<String>){
fun f()="0123456789abcdef".get((Math.random()*16).toInt())
var s=""
for(i in listOf(8,4,4,4,12)){
for(j in 1..i)
s+=f()
if(i!=12)s+="-"}
println(s)}

Try it online!

My first ever Kotlin program & PPCG submission

Answer 14

APL (Dyalog Unicode), 115 78 bytes

a←⊣,'-',⊢
H←⊃∘(⎕D,819⌶⎕A)¨16∘⊥⍣¯1
(H 8?16)a(H 4?16)a(H 4?16)a(H 4?16)a H 12?16

Try it online!

This is my first APL submission. Huge thanks to @Adám for bearing with me at the PPCG's APL chat and for the hexadecimal conversion function.

Thanks to @Zacharý for 1 byte

Edited to fix byte count.

Answer 15

Japt, 32 bytes

[8,4,4,4,12]m@MqG**X sG ù0X} q"-

Try it online!

Answer 16

Perl 6, 53 bytes

The obvious one:

say join '-',(0..9,'a'..'f').flat.roll(32).rotor(8,4,4,4,12)».join # 67

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Translating the Perl 5 example using printf, results in code that is a bit shorter.

printf ($_='%04x')~"$_-"x 4~$_ x 3,(0..^4⁸).roll(8) # 53

Answer 17

Perl, 51 bytes

say"xx-x-x-x-xxx"=~s/x/sprintf"%04x",rand 65536/reg

Requires perl5 >= 5.10 I think. For the /r modifier and for say().

Answer 18

C++, 194 193 221 210 201 bytes

+7 bytes thanks to Zacharý ( detected a - that should not be at the end )

#include<iostream>
#include<random>
#include<ctime>
#define L(a)for(int i=0;i<a;++i)std::cout<<"0123456789abcdef"[rand()%16];
#define P(a)printf("-");L(a)
void t(){srand(time(0));L(8)P(4)P(4)P(4)P(12)}

If someone has a way to get a different value every execution without changing srand and without including <ctime>, that would be great

Answer 19

J, 42 39 37 27 bytes

echo'-'(8+5*i.4)},hfd?36#16

Try it online!

Answer 20

Befunge-93, 97 bytes

v>4448v,+<    <
0*    :  >59*0^
62v0-1_$:|>*6+^
>^>41v < @^99<
v<*2\_$:54+` |
?0>+\1-^ v*68<>
>1^

Try it online!

I'm sure this can be shrunk, but this is my first try :)

Answer 21

Bash, 67 bytes

for l in 4 2 2 2 6;{ o+=`xxd -p -l$l</dev/random`-;}
echo ${o::-1}

Answer 22

C (gcc), 143 110 103 96 94 bytes

Golfed down to 94 bytes thanks to ceilingcat and Jonathan Frech.

(*P)()="\xf\x31À";*z=L"\10\4\4\4\14";main(n){for(;*z;*++z&&putchar(45))for(n=*z;n--;printf("%x",P()&15));}

Try it online!

Explanation:

/*
  P is a pointer to a function.
  The string literal contains actual machine code of the function:

  0F 31     rdtsc
  C3        ret

  0xc3 is the first byte of the UTF-8 representation of the character À
*/
(*P)() = "\xf\61À";

// encode uuid chunk lengths as literal characters
// we use wide characters with 'L' prefix because
// sizeof(wchar_t)==sizeof(int) for 64-bit gcc C on TIO
// so z is actually a zero-terminated string of ints
*z = L"\8\4\4\4\14"

main (n)
{
    for (
        ; 

        // loop until we reach the trailing zero
        *z;

        // increase the pointer and dereference it
        *++z 
             // and output a hyphen, if the pointer does not point at zero
             && putchar(45) 
    )
        // output a random hex string with length pointed at by z
        for (n = *z; n--; printf ("%x", P()&15));
}

Answer 23

C (gcc),  94   91  86 bytes

main(i){srand(&i);i=803912;for(;i--%16||(i/=16)&&printf("-");printf("%x",rand()%16));}

Try it online!

I would have liked to suggest this version in a comment to Max Yekhlakov (his answer), but unfortunately I do not have the 50 needed reputation points yet, so here is my answer.

803912 is C4448 in hexadecimal, it describes how the output should be formatted (12-4-4-4-8), it is reversed because least significant digits will be read first.
 

Edits:

• saved 3 bytes thanks to Jonathan Frech
• saved 5 more bytes by replacing srand(time(0)) with srand(&i)

Answer 24

JavaScript REPL, 79 bytes

'66-6-6-6-666'.replace(/6/g,_=>(Math.random().toString(16)+'00000').slice(2,6))

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Math.random may return 0. Adding 5 zeros make the slicing get 4 0s

Answer 25

Forth (gforth), 91 89 bytes

include random.fs
hex
: f 0 4 4 4 8 20 0 do dup i = if + ." -" then 10 random 1 .r loop ;

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Explanation

Changes the base to hexadecimal, then outputs numbers/segments of the appropriate length with dashes at specified intervals

Code Explanation

include random.fs          \ include the random module
hex                        \ set the base to hexadecimal
: f                        \ start a new word definition
  0 4 4 4 8                \ enter the intervals to place dashes
  20 0 do                  \ start a counted loop from 0 to 0x20 (32 in decimal)
    dup i =                \ check if we are on a character that needs a dash
    if                     \ if we are
      +                    \ calculate the next character that gets a dash
      ." -"                \ output a dash
    then                   \ end the if block
    f random               \ get a random number between 0x0 and 0xf
    1 .r                   \ output it right-aligned in 1-character space
  loop                     \ end the loop
;                          \ end the word definition

Answer 26

Java with Ten Foot Laser Pole v. 1.06, 126 bytes

String u(){return sj224.tflp.util.StringUtil.replace("aa-a-a-a-aaa","a",s->String.format("%04x",(int)(Math.random()*65536)));}

Tested with version 1.06 of the library, but this should work with any version 1.04 or newer.

Answer 27

MATLAB/Octave , 95 bytes

a='-';b=strcat(dec2hex(randi(16,32,1)-1)');[b(1:8) a b(9:12) a b(13:16) a b(17:20) a b(21:32)]

Answer 28

Tcl, 95 bytes

time {append g [format %x[expr [incr i]%4|$i<7|$i>21?"":"-"] [expr int(rand()*16)]]} 32;puts $g

Try it online!

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Tcl, 97 bytes

time {append g [format %x[expr [incr i]%4||$i<7||$i>21?"":"-"] [expr int(rand()*16)]]} 32;puts $g

Try it online!

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Tcl, 98 bytes

time {incr i;append g [format %x[expr $i%4||$i<7||$i>21?"":"-"] [expr int(rand()*16)]]} 32;puts $g

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Tcl, 101 bytes

time {incr i;append g [format %x[expr !($i%4)&&$i>7&&$i<21?"-":""] [expr int(rand()*16)]]} 32;puts $g

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Tcl, 104 bytes

proc D {n\ 4} {time {append g [format %x [expr int(rand()*16)]]} $n;set g}
puts [D 8]-[D]-[D]-[D]-[D 12]

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Answer 29

Jelly, 17 bytes

ØhWẋ36X€”-“µÇŒð‘¦

Try it online!

Answer 30

SmileBASIC, 65 62 bytes

DEF G H?"-";:END
DEF H?HEX$(RND(65536),4);
END H G G G G H H H

I created a function to print 4 random hex digits: DEF H?HEX$(RND(65536),4);:END as well as 4 digits with a - after them: DEF G:H?"-";:END. Then it just has to call these functions a bunch of times.

Answer 31

Chip, 109 + 6 = 115 bytes

Requires flags -wc36, causing +6 bytes

!ZZZZZZZZZZZZZZZZZZZZZZ
,-----.,+vv--^----^---z
?]]]--R\acd
?xx+-)\\b
?x+x-)\\c
?^xx\--\d
`-xx]v~\e
f*`)'`-\g

Try it online!

Generates 4 random bits (the four ?'s) and converts to hex digits:

• 0x0 - 0x9 => 0 - 9
• 0xa - 0xe => b - f
• 0xf => a

...a bit unconventional, but it saved me some bytes at no expense to the distribution of outcomes.

Answer 32

Ruby, 51 47 + 14 = 65 61 bytes

Run with ruby -rsecurerandom (+14 bytes)

[8,4,4,4,12].map{|n|SecureRandom.hex n}.join ?-

Returns output

Answer 33

Java, 192 181 bytes

interface T{static int t(){return (int)(Math.random()*65536);}static void main(String[]a){System.out.printf("aa-a-a-a-aaa".replaceAll("a","%04x"),t(),t(),t(),t(),t(),t(),t(),t());}}

Answer 34

Octave, 106 105 103 99 96 bytes

function[]=f,g=@(l)[48:57,'a':'f'](randi(16,[1 l]));strjoin({g(8),g(4),g(4),g(4),g(12)},'-'),end

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Answer 35

Pyth, 34 bytes

VS32 aYO16)s.e?}km*d4r2 6+\-bb.HMY

Try it online!

trying to generate the indexes of where the "-" should go, and doing the replacement in a smaller way than hardcoding was an interesting challenge, and probably the hardest part.

Explanation

VS32 aYO16)                          // for N in range(32), append a random number 0-15 to the list Y
                              .HMY   // convert each number in Y to its Hex equivalent
                 m*d4r2 6            // make an array (of indexes) containing [8 12 16 20]. *4 mapped over (range(2,6) -> [2,3,4,5])
            .e                       // enumerating map on the random hex list. For each digit, index is k and value is b.
              ?}k        +\-bb       // map onto each digit the ternary question "is index k in the array of idexes?"
                                     // if no, replace with b (the value that was already there), if yes replace it with "-b".
           s                         // "".join( ) to make the list into a string

Answer 36

MBASIC, 92 bytes

1 FOR I=1 TO 32:PRINT HEX$(INT(RND*16));:IF I=8 OR I=12 OR I=16 OR I=20 THEN PRINT"-";
2 NEXT

Generates 32 "random" hex digits, adding a hyphen in the appropriate places.

Output:

D36A49D6-85AC-51DC-6D84-3BB1EB1A0816

Answer 37

Pushy, 34 bytes

12N4448s$:Z15U&T)?39+;48+'.;L?45'.

Try it online!

12                                 \ Push 12 to stack
  N                                \ Remove printing delimiter (normally a newline)
   4448s                           \ Push 4448, then split into digits
                                   \ The stack is now [12, 4, 4, 4, 8]
        $                          \ While items left on stack:
         :                         \ (top item) times do:
          Z15U                     \    Push random(0, 15)
              &T)?                 \    If bigger than 10 (a hex digit):
                  39+;             \      Add 39 (offset from ASCII numbers to lowercase)
                      48+          \   Add 48, converting it into the correct character
                         '.        \   Print and pop this character
                           ;L?45'. \ Print a dash ('-'), unless stack is now empty.

Answer 38

05AB1E, 19 bytes

ŽΣÌvy4*F15ÝΩh}'-}J¨

Try it online.

Explanation:

ŽΣÌ                   # Compressed integer 21113
   v            }     # Loop over each of its digits `y`
    y4*               #  Multiply `y` by 4
       F     }        #  Loop that many times
        15Ý           #   Create a list in the range [0,15]
           Ω          #   Pick a random number from it
            h         #   Convert it to hexadecimal
              '-     '#  Push string "-"
                 J    # After the loops, join the entire stack together
                  ¨   # And remove the trailing "-" (and output the result implicitly)

See this 05AB1E tip of mine (section How to compress large integers?) to understand why ŽΣÌ is 21113.

Answer 39

Python 3.8 (pre-release), 31 bytes

import uuid;print(uuid.uuid4())

Try it online!

Python has an inbuilt package for this specific task. Enjoy :P

Answer 40

JavaScript (ES6), 79 bytes

a=>[8,4,4,4,12].map(g=e=>e?(16*Math.random()|0).toString(16)+g(e-1):"").join`-`