Spew Id

It’s a command-line utility to generate unique identifiers (UUID, ULID, ObjectId) written in Rust.

The executable name is spwd, which is a vowelless continuous writing of “spew id” — easy to remember and quick to type.

Motivation

Sometimes I just need a random identifier, sometimes not so random. Sometimes it’s an ObjectId, yet sometimes it’s a UUID v7. Sometimes I need ten of those. And what is the simplest and fastest way to get one? Is it REPL, web search, or a terminal? Probably the latter. Especially if I want it in my shell scripts. But what options do I have?

For UUID, it’s the standard uuidgen. How standard? Well, the macOS version is quite limited. And brew search uuid gives me one other option from 2008. Can I build the Linux version of uuidgen? Sure. Do I want to do it? Not really.

For ULID, there’re no standard options, and brew search ulid gives nothing useful. There are a few options in the wilds, like timclicks/ulid-lite and technosophos/ulid, but nothing I can simply brew install.

For ObjectId, which is my favorite, there’s nothing. Nope, I’m not counting anything JavaScript. With mongosh, it’s quite easy to write a shell function that’ll do the job, but doesn’t it require Node.js? Well, thank you, but no, thank you.

As for an option that covers all three, I never found one. So, it turns out, the simplest way right now is to use web search or the online tools I found earlier. And that’s quite sad.

UPD: Later I found various implementations among crates.io packages but none of those ticked all my boxes and were available through Homebrew.

So, here’s my take on a single utility — a one-stop shop if you like — to cover all those cases.

Usage

The spwd is available as stand-alone binaries, Cargo and Homebrew packages, and a container image.

Binaries can be found on the repo’s releases page. If there’s no platform you’re looking for, you can compile an appropriate binary yourself. Or feel free to create a PR or an issue.

The Cargo package can be installed as usually:

cargo install spwd

The Homebrew package can be obtained through the tap:

brew install aeron/tap/spwd

The container image is available as docker.io/aeron/spwd and ghcr.io/Aeron/spwd. You can use them both interchangeably.

docker pull docker.io/aeron/spwd
# …or…
docker pull ghcr.io/aeron/spwd

Arguments

Running the app with -h or --help option will give you the following:

Usage: spwd [OPTIONS] <COMMAND>

Commands:
  uuid  Generate a new UUID
  ulid  Generate a new ULID
  oid   Generate a new ObjectId

Options:
  -n, --num <NUMBER>  Number of results [default: 1]
  -h, --help          Print help
  -V, --version       Print version

Simply run --help for a certain command to see command-specific options.

For usage examples, see USAGE.md.

Identifiers

UUID

UUID (Universally Unique Identifier) supports versions 1, 3, 4, 5, 6, 7, and 8. Version 4 (random) is the default.

Version	Algorithm	Extra Options
1	Time-based, MAC address node	--timestamp (ns), --node-id
3	Name-based, MD5	--namespace, --name (both required)
4	Random (default)	—
5	Name-based, SHA-1	--namespace, --name (both required)
6	Reordered time-based, sortable	--timestamp (ns), --node-id
7	Unix Epoch time-based, sortable	--timestamp (ns)
8	Custom	--data (hex-encoded 16 bytes, required)

Supported namespaces for versions 3 and 5: dns, oid, url, x500.

ULID

ULID (Universally Unique Lexicographically Sortable Identifier) is a 26-character, Crockford Base32-encoded identifier composed of a 48-bit millisecond timestamp and 80 bits of randomness. It is always monotonically sortable.

Accepts an optional --timestamp in milliseconds.

ObjectId

ObjectId is a 12-byte (24 hex character) MongoDB/BSON identifier composed of a 4-byte Unix timestamp, a 5-byte random value, and a 3-byte incrementing counter.

Available via both oid and objectid commands. Accepts an optional --timestamp in seconds.

Performance

In case the performance is a consideration, here are the benchmarks against the standard uuidgen utility (macOS 26.3 @ Apple M1 Max):

$ hyperfine --warmup 10 -N 'target/release/spwd uuid' 'uuidgen'

Benchmark 1: target/release/spwd uuid
  Time (mean ± σ):       1.7 ms ±   0.1 ms    [User: 0.8 ms, System: 0.5 ms]
  Range (min … max):     1.5 ms …   3.1 ms    1528 runs

Benchmark 2: uuidgen
  Time (mean ± σ):       2.5 ms ±   0.2 ms    [User: 1.2 ms, System: 0.6 ms]
  Range (min … max):     2.3 ms …   3.2 ms    1218 runs

Summary
  target/release/spwd uuid ran
    1.52 ± 0.15 times faster than uuidgen

Acknowledgments

This project relies on the following excellent libraries for identifier generation:

• uuid by uuid-rs, available under Apache-2.0 OR MIT
• bson by MongoDB Inc., available under MIT
• ulid by Dylan Hart, available under MIT