C Library Functions  - generate_uuid (3)

NAME
generate_uuid(3f) - [M_uuid] generate a UUID (Universally Unique IDentifier) string per RFC 4122 (LICENSE:BSD-4-Clause)

CONTENTS

Synopsis
Description
Authors
Options
Examples

SYNOPSIS
interface: 

       function generate_uuid(version) result(uuid)
       integer, intent(in), optional :: version
       character(len=36)             :: uuid

DESCRIPTION
A universally unique identifier (UUID) is a 128-bit number used to identify information in computer systems. When generated according to standard methods UUIDs are for practical purposes unique. generate_uuid(3f) converts the UUID to a standard string format per RFC 4122.

AUTHORS
based on previous work from Alberto Garcia & Jon Wakelin, 2003-2004. RNG routines from Scott Ladd <scott.ladd@coyotegulch.com>, and the libFoX library( Toby White <tow@uszla.me.uk>, Gen-Tao Chiang <gtc25@cam.ac.uk>, Andrew Walker <a.walker@ucl.ac.uk>).

OPTIONS
version
  Indicates which standard method as described in RFC 4122 is used to generate the string. Versions 0,1, and 4 are supported.
0. Nil UUID (ie. ’00000000-0000-0000-0000-000000000000’)
1. time-based UUID
2. Not implemented
3. Not implemented
4. pseudo-RNG(Random Number Generator) based
5. Not implemented

EXAMPLES
Sample usage: 

     program demo_generate_uuid
     ! generate 36-character UUID string
     use M_uuid, only : generate_uuid
     implicit none
     character(len=36)   :: uuid
     character(len=4096) :: filename
        !
        ! version 1 (time-based UUID)
        uuid=generate_uuid(version=1)
        write(*,’(a36)’)uuid
        !
        ! version 4 (pseudo-RNG-based), default
        uuid=generate_uuid(version=4)
        write(*,’(a36)’)uuid
        !
        ! RFC 4122 defines a Uniform Resource Name (URN) namespace for UUIDs.
        write(*,’("urn:uuid:",a36)’)uuid
        !
        ! a good scratch file name
        open(file=’/tmp/scratch_’//uuid,unit=10)
        inquire(unit=10,name=filename)
        write(*,’(*(g0))’) trim(filename)
        close(unit=10,status=’delete’)
     end program demo_generate_uuid
Results: 

   > afa6bfb4-65a3-11ef-7251-52dbfec73ce6
   > 717b923d-c12f-4d99-6446-21b4fbed1337
   > urn:uuid:717b923d-c12f-4d99-6446-21b4fbed1337
   > /tmp/scratch_717b923d-c12f-4d99-6446-21b4fbed1337

Nemo Release 3.1 generate_uuid (3) June 29, 2025
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