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Comment by geostyx | Hacker News Reader

Maybe you want a UUID within a shell script, CI/CD pipeline or orchestration framework which has native support for HTTP, but not UUID :)

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Little known feature on Linux:

    cat /proc/sys/kernel/random/uuid

Also:

  uuid -r

See https://linux.die.net/man/1/uuid

What's the -r do? Output as raw bytes? I always just do `uuid -v4`

-r is for "random". I've needed it for one of my scripts: if you generate many UUIDs at once on the same machine, there will be duplicates.

I believe v4 is what you actually want [1]. By default it looks like `uuid` generates a v1 id, which as you said will produce duplicates if you call it too quickly.

Maybe your tool is different from the one installed on my machine because when I use the `-r` option I just get garbage back. This leads me to believe it's returning the uuid as raw bytes when I pass that option.

   $ uuid
   97af2898-cb54-11ea-8d75-176c10241ffd
   $ uuid -v4
   0b8d75f5-a148-466c-b1b5-9d9d1022c327
   $ uuid -r
   ����T꧚�����.

[1] https://en.wikipedia.org/wiki/Universally_unique_identifier#...

I checked in my code, I actually used `uuidgen`, not `uuid`. Thus the mixup!

Awesome, thanks! I will read up on that! Wonder if it's as stable as using dedicated uuid programs or libraries.

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