Show HN: Givemeguid.com – CLI/curl friendly GUIDs | Hacker News Reader

Show HN: Givemeguid.com – CLI/curl friendly GUIDs

givemeguid.com

32 pointsdeweyair46 comments

I'm having trouble imagining who would want to use this. What's the environment where you would have curl and a need for generating UUIDs, but wouldn't have access to uuidgen or similar?

Yeah, I'm just really confused. If you're at a CLI, you probably have uuidgen. And I'd assume there's something similar on Windows.

If you're writing some kind of application, pretty much every language/framework can generate UUIDs, and even if yours doesn't, just generate a 128-bit number, stamp the v4 UUID bits into it, reformat it, and you're done. Calling out to a 3rd-party service is insane for that use case anyway.

> Yeah, I'm just really confused. If you're at a CLI, you probably have uuidgen. And I'd assume there's something similar on Windows.

uuidgen is provided by the Windows SDK - exactly the same usage than in *nix

Understandable! I made it for the few times I'm manually testing an API using Swagger or something similar and need a valid(ish) GUID to stand in for some field being sent to the api.

There's no shortage of ways to generate GUIDs, that's for sure!

This, and also, are GUID that pose a problem with CLI/curl really a thing?

Maybe a JS App which is made completely out of third party APIs, without anything self-hosted? Not discussing wether this is a good idea or not, though...

I was surprised to see that there is no "built-in" mechanism in JS to generate a GUID. As a C# dev, I'm used to Guid.NewGuid()

Why would you make an http request if you can just google a 3-line JS solution? You're just generating a large random number and formatting it as a UUID.

https://gist.github.com/jed/982883

If you google "generate uuid javascript" you can find approaches from Math.random to node/browser `crypto` module to shelling out OS random.

One of the main benefits of guid generation is that you don't need to synchronize with anything to generate a unique ID, so it's weird to incur an http request, especially to someone else's service. At that point you might as well just phone home to your own service.

JavaScript Math.random() should never be used for UUID generation. You will get collisions even at small scale.

window.crypto.getRandomValues() should be used instead.

The quality and seeding of Math.random() is implementation-dependent and not generally good enough everywhere to prevent collisions. Many seed with the just the system time.

Source: I have personally seen such collisions in a production web app with 700k users. A Web search for “Javacsript GUID collision” shows that many others have as well. We switched to the cryptographic generator and the collisions disappeared.

UUIDs also have a hashed namespace in them, don't they? Not sure if that version implements them.

Only uuid v3/v5. Anything is possible if that's what you want. But 128 (or 122) bits of random are usually what you want when you think of guid.

Most people format 128-bit random numbers into a UUID just so it's obvious at a glance what it is: a guid. Even if it's not technically a UUIDv4 because it doesn't have the magic bits.

In what world is it safe to rely on an external service to provide GUIDs for you? Where's the guarantee that the service won't one day start manipulating GUIDs? Now you have a major attack vector.

> major attack vector

That seems hyperbolic to me. If you rely on UUID for security, it seems, to me, something is wrong in your architecture and the security flaw lies there.

When would you, legitimate, rely on GUID/UUID for security?

You can totally use uuid4 as password reset tokens, and they could be slightly nicer than random urlsafe strings for your database, provided they’re generated securely, not from givemeguid.com.

You can use the UUID v4 as a secret I guess.

If a programmer isn't able to code a GUID generator and uses a HTTP request instead, he really shouldn't code.

Depends on the GUID. Some of them include version numbers, timestamps etc... I would need to code the http request too. The problem with web services is that they might disappear again, so I would maybe use it on a website, but not for production software.

Quick GUID's in JavaScript

    Math.random().toString(32).slice(2,10)

Gives you an 8 character GUID.... but maybe don't use it for anything important....

Maybe a NPM module for generating UUIDs? /s

If you use Linux:

cat /proc/sys/kernel/random/uuid

This doesn't work on macOS :(

cat: /proc/sys/kernel/random/uuid: No such file or directory

I edited, it's a Linux feature.

TIL something new, thanks!

Is this just a "random" UUID or does it meet specs of RFC 4122? I have seen countless times when it was just generated as {8}-{4}-{4}-{4}-{12} with complete random numbers. Well, works for most applications...

This is what I use to generate guids with autohotkey: ::;guid:: guid := GUID() StringLower, guid, guid Clipboard := guid SendInput,^v return

GUID() { format = %A_FormatInteger% ; save original integer format SetFormat Integer, Hex ; for converting bytes to hex VarSetCapacity(A,16) DllCall("rpcrt4\UuidCreate","Str",A) Address := &A Loop 16 { x := 256 + *Address ; get byte in hex, set 17th bit StringTrimLeft x, x, 3 ; remove 0x1 h = %x%%h% ; in memory: LS byte first Address++ } SetFormat Integer, %format% ; restore original format h := SubStr(h,1,8) . "-" . SubStr(h,9,4) . "-" . SubStr(h,13,4) . "-" . SubStr(h,17,4) . "-" . SubStr(h,21,12) return h }

I will just leave it here: https://www.uuidgenerator.net/api

And why would you do that?

It looks very relevant and has more features?

Well, yeah, of course. The link itself is fine, it's the remark next to it that I find to be in poor taste and uncalled for.

I remember several years ago using https://newguid.com which was pretty much the same thing - no page furniture, just the new guid. Sadly the domain seems to be on sale now!

There's also https://www.newguid.org/

> Sadly the domain seems to be on sale now!

Which is a perfect example why it is bad to rely on a service like this to generate your IDs.

What if I bought it and started emitting predictable IDs? Or non-unique IDs?

Usage information in response headers, me like :)

Thanks!

Nice! I think this will still have a use and is a nice addition to add another alternative way to generate uuids

I use the following alias to generate uuids

   function uuid() { uuidgen | tr "[:upper:]" "[:lower:]" | tr -d "\n\r" }

I then pair it with pbcopy on the mac

   uuidgen | pbcopy

one of my most used non-trivial shell commands must be

    uuidgen | awk '{ printf "\"" $1 "\"" }' | xclip -selection clipboard

Instructions are in the headers. Query string params for returning multiple GUIDs, and optionally returning JSON.

- https://www.givemeguid.com/?json=1

- https://www.givemeguid.com/?number=5

If you use Visual Studio, typing the word (with quotes) “nguid” in the code IDE generates one for you.

I spend a fair amount of my day in Visual Studio and didn't know this, thanks!

I made one for fun (and as a QA exercise for my GF): https://aloisdegouvello.gitlab.io/guid/ GUID as a service. What a time to be alive :)

If you need a unique identifier on the command line there are a few ways to do it.

uuidgen is one. My personal favorite is this snippet.

$ id=$(openssl rand 1000 | openssl sha1) && printf "%s${id:0:8}\n"

Why would you want to hash random bytes? The only thing you could theoretically achieve by that would be decreasing entropy. Just do openssl rand -hex 20 (or any other number of bytes as needed, or -base64 for another encoding).

I have uuidgen in my Mac, but also have a tiny alias:

    alias uuid='python -c "import uuid;print(str(uuid.uuid4()))"'

Thanks I'll probably use this. I often want to get a static uuid - usually for adding as static data in a test.

Or from PowerShell: [Guid]::NewGuid()

Which is in turn, derivated from .NETs 'Guid.NewGuid()'

> New-Guid

Is shorter and easier.

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